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Araújo Jr., W.P. and Asp, N.E., 2013. Hydrodynamic connectivity between two macrotidal Amazonian estuaries
The hydrodynamic connectivity between the Taperaçu and the Caeté estuaries at the east sector of the Amazon Coastal Zone, through the Taici channel was investigated. Water levels, currents, salinity and suspended solid concentration (SSC) were measured at both ends and at the middle of the channel. The measuring campaigns were carried out during neap and spring tides, including also the wet and dry seasons. The results have showed a strong tidal asymmetry, with ebb phases lasting approx. 40% longer than the flood. On the other hand, the flood phase is longer and takes place first and reaches higher levels at the Caeté side in comparison to the Taperaçu side, despite neap/spring or wet/dry variations. During the wet season the depth-integrated ebb current velocity reached 1.5 m.s−1 at the Taperaçu side and 1.4 m.s−1 at Caeté side, whereas during the flood it reached 0.9 and 0.8 m.s−1 at Taperaçu and Caeté sides, respectively. During dry season velocities were smaller, especially during the ebb. Maximum SSC was around 1 g.L.−1 during neap tides, whereas during the spring tide the SSC reached 2 g.L−1 at the Taperaçu and 1.5 g.L−1 at the Caeté side. Beside current direction, the salinity was meaningful for the investigation of the hydrodynamic connectivity, as the Taperaçu and Caeté waters show important salinity differences. Combining hydrodynamic data, SSC and salinity, it is possible to state that there is an effective hydrodynamic connection between the estuaries through the Taici channel. The connection is represented by the water flux from Caeté into the Taperaçu during the beginning of the flood phase, which took place first at the Caeté side in all measured situations. This is caused by the substantial infilling of the Taperaçu hindering the incoming tidal wave, as well as by the differences in estuarine position and orientation. Thus, a Caeté to Taperaçu pressure gradient is established, resulting in the observed flow. However, this flux is reduced at neap tides, especially during the dry season, due to lower water levels. When the tide also rises at the Taperaçu, that flow is interrupted. During the ebb phase there is no evidence of the opposite process. Therefore, the flux between the estuaries is effective and is the result of a complex interaction of tidal asymmetry, tide delay between the estuaries, seasonal variations of precipitation and fluvial discharge, as well as morphologic differences among the estuaries.
Asp, N.E., Freitas, P.T.A., Gomes, V.J.C. and Gomes, J.D., 2013. Hydrodynamic overview and seasonal variation among the estuarine diversity at the eastern sector of the Amazon coast. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
At the eastern sector of the Amazonian coast a macrotide, abundant rainfall and a low relief result in numerous estuaries. According to variation in rainfall, fluvial discharge and geology, there is also a substantial variation among these estuaries. To evaluate this diversity, short measuring campaigns were carried out, including currents, water levels, discharge, salinity, bathymetry and sedimentology. Results indicate four main types of estuary: typical macrotidal estuaries; estuaries with large fluvial discharge; shallow, frictionally-dominated macrotidal estuaries, with negligible fluvial discharge; and estuaries with structural control. At the typical macrotidal type the ebb phase was longer than the flood, however the current velocities tend to be higher during the ebb, due to substantial fluvial discharge influence, especially during the wet season. Regarding salinity, longitudinal gradient and vertical homogeneity is observed. Mean water depth is at the same order of the tidal range. Mean fluvial discharge varies from several tens to few hundreds, within this category. Where the fluvial discharge is negligible, there is no significant longitudinal salinity variation, although the seasonal variation is substantial. There, substantial asymmetry and flood dominance is observed. However, there is no substantial seasonal variation in the current pattern. Mean depths are small, compared to the tidal range. However, some river valleys and estuaries seem to be associated to local faults and present depths of up to ten times the tidal range and relatively weak currents. Results have showed that the differences are substantial among the estuaries, although they are closely located and similar in form.
Carol, E; Kruse, E and Tejada, M, 2013. Surface water and ground water response to the tide in coastal wetlands: Assessment of a marsh in the outer Río de la Plata estuary, Argentina
On the coast of the outer Río de la Plata estuary (Argentina) there is a vast coastal wetland occurring in a marsh environment. The hydrodynamics of this wetland is subject to a semidiurnal microtidal regime which causes a wedge of estuary salt water to penetrate below the freshwater coming from continental discharge. This paper analyzes the hydrodynamics of surface and groundwater, and it assesses how anthropogenic changes affect the natural hydrological behavior of the coastal wetland in the southern sector of the outer Río de la Plata estuary. Water level and temperature measurements were carried out on water from the canals flowing into the estuary and the phreatic aquifer located in the marsh. The salinity of the water column was measured at one high tide which was above and one which was below the regional groundwater discharge level. The results show that in natural conditions the wetland has a complex hydrological behavior conditioned by the tidal flow. Surface and groundwater saline stratification is a distinctive characteristic, and the variations in level, temperature and salinity of groundwater depend on its interaction with estuary and continental water. At present, 47 % of the marsh is excluded from the tidal cycle due to anthropogenic action (levees, roads and canals with floodgates), causing a major alteration to the hydrological behavior and the environmental characteristics of the wetland.
Costa, A.K.R., Pereira, L.C.C., Costa, R.M., Monteiro, M.C. and Flores-Montes, M., 2013. Oceanographic processes in an Amazon estuary during an atypical rainy season. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
This study examined short-term and spatial fluctuations in hydrodynamic and hydrological variables in an Amazon estuary (Taperaçu). The campaign was conducted during the neap tide of an atypical rainy season (April, 2012). Three stations were established in the upper, middle and lower sectors of the estuary to obtain surface and bottom data during flood and ebb tides. Water samples were collected simultaneously in Niskin bottles to determine pH and chlorophyll a levels. In the mid-estuary sector, a mooring was mounted to the bottom with a tide data logger, a CTDO and a mini-current meter for 25 hours. Precipitation levels in April, 2012, were 31% lower in comparison with the same month of the previous year, reflecting the effects of an El Niño event. The temperature of the water was high and stable, varying from 28.5 to 30°C. Salinity was higher and turbidity was lower when compared to a typical rainy season. The higher levels of dissolved oxygen in the lower sector of the estuary appear to be related to the greater hydrodynamic energy in this sector, where wave forces increase the exchange of oxygen in the water-air interface. The lower turbidity appeared to have promoted an increase in chlorophyll a concentrations due to a higher penetration of sunlight, mainly in the upper sector. Many variables recorded in the present study appear to have deviated from the typical range of values for the time of year due to the below-average precipitation recorded during the first half of 2012 (rainy season) in the study area.
Costa, M. S., Rollnic, M., Silveira, O. F. M., Miranda, A. G. O. and Santos, R. R. L. 2013. Morphological and sedimentological processes of an Amazon Estuary, Maguari River (Pará - Northern Brazil). Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1110–1115, ISSN 0749-0208.-->
The Maguari river is an area influenced by both tide and waves with gentle declivity from downstream to upstream to provide until −42 m depth, averaging 24m in the channel and −5m in the margins and distal areas. These sectors offer hazard to navigation by exposing muddy-sandy bars. The river expresses the geological evolution of the region, having been originated by a tectonic fault oriented to NW-SE, through a filling process. Furthermore, it is characterized as importer of the sediments masking channel dimensions confirmed by the high current speeds. The river has about 65% of the substrate covered by mud, with extensive tidal flats. According to the sedimentological analysis, the environment has a high to very high hydrodynamic pattern ranging from silt to sandy-silt according to ratings. The low concentrations of clay show that the environment is highly energetic agreeing with other studies in the region. The organic matter concentration ranged from 0 to 12.5% with peak concentrations in the clay samples, being the entry to various chemical reactions.
Costa, K.G., Bessa, R.S.C., Pereira, L.C.C., Costa, R.M., 2013. Short and medium-term changes of Pseudodiaptomidae copepods in the Amazonian Mangrove Coast: the Paracauari River estuary. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Given the importance of copepods in pelagic food webs, short- and medium-scale temporal variation in the distribution and abundance of copepods of the genus Pseudodiaptomus was investigated in an oligo-mesohaline estuary (Paracauari) in northern Brazil. This system is characterized by high local hydrodynamics and nutrient input from the Paracauari River and Marajó Bay, and marked seasonal variation in rainfall levels. The temporal variation in the abundance of copepods was analyzed in the context of some hydrological variables — tide height, salinity, temperature, pH, and concentrations of suspended particulate material, dissolved oxygen and chlorophyll a. Samples were collected in 2009 at a fixed station (00°44′15.4″S, 48°31′07.5″W) every 3 hours during a nycthemeral cycle in the neap and spring tides of February, May, June, August, November, and December. Zooplankton samples were collected using horizontal hauls of plankton nets with a 120 μm mesh. Following identification, the abundance and density of Pseudodiaptomus copepods were determined. Data were analyzed using an ANOVA (to assess the significance of diurnal, fortnightly and seasonal variations), PCA, and Bray-Curtis similarity. Four species were identified: Pseudodiaptomus richardi, Pseudodiaptomus marshi, Pseudodiaptomus gracilis, and Pseudodiaptomus acutus. The results indicate that variation in composition and density of the Pseudodiaptomidae copepods in the Paracauari estuary is determined by the interactive effect of the freshwater influx from Marajó Bay, tides, and the rainfall regimen, which modulate local salinity. The absence of diurnal variation in species composition and density was determined by the high local hydrodynamics, which provoke the constant mixing of the estuary's water.
Ernstsen, V.B., Lefebvre, A., Kroon, A. and Niemann, S.L., 2013. Oblique second-order sand transport patterns on an intertidal sand flat in a natural tidal inlet system. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
A detailed digital elevation model (DEM) of an intertidal sand flat in the Knudedyb tidal inlet in the Danish Wadden Sea, derived from high-resolution Light Detection And Ranging (LiDAR) data, reveals a large elongated bedform field with complex bedform morphologies and drainage channel networks. This indicates distinct second-order sand transport pathways oblique to the main tidal transport pathways. A conceptual model for the development of the bedforms and channels is presented, which comprises hypotheses of the hydrodynamic forcing of the different second-order sand transport pathways. During flood tide, sand is transported along ESE-oriented pathways across the intertidal flat towards the inner tidal basin. During the late stages of ebb tide, sand is transported in drainage channels (WSWoriented) from the intertidal flat towards the inlet channel. During storm events with winds from SW, wave-generated currents transport sand along a NE-oriented transport pathway from the inlet channel towards the intertidal flat.
Fernandes, A., Figueira de Sousa, J., Vicente, T., Ferreira, J. C., 2013. Challenges to an Integrated Delta Approach: the case of the Tagus Estuary In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The Tagus estuary is the largest wetland and estuary in Portugal and one of the most important estuaries in Europe. This estuary occupies a central position in the territorial context of the Lisbon Metropolitan Area. However, the competitive relationship between the multifunctional land uses and economic activities present in this estuary and the specific ecological values of the area, result in an unbalanced development of the estuary. The exchange of experiences with other estuary and delta regions through the Deltanet Project, proved that the Tagus estuary faces important challenges in finding a balance between economic development (port development, tourism) and the ecological conservation of this estuary. In this sense, the present article aims: (i) to identify the main problems in the Tagus estuary in the context of an integrated Delta approach; (ii) to present the lessons learnt from other estuary/delta regions in a benchmarking exercise and (iii) to propose good practices for a better integrated delta approach in the Tagus estuary. Based on the authors' experience in the Deltanet Project, the article is structured in four main parts: (i) summary of physical and human features of the Tagus estuary, (ii) institutional framework, (iii) identification of the main problematic issues, (iv) good practices and lessons learnt by the Tagus estuary. Focusing these lessons, the article concludes that only by developing and integrated approach is it possible to deal with the very dynamic development of urbanization, economic activities, infrastructure, natural and technological risks faced by delta and estuary regions.
Gaspar, F.L; Montes, M. de J.F; Nascimento-Filho, G.A.;Lins, I.C.; Paulo, J.G.; Longo, A.P. 2013. Spatial and seasonal sediment phosphorus species and its relation with granulometry, organic matter and CaCO3 in a tropical estuary In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The identification of phosphorus species in sediments is a useful approach for the assessment of potential sources or sinks of phosphorus in estuarine regions, and helps to understand the biogeochemical processes that control the availability of phosphorus in tropical areas. This study aimed to identify the spatial and seasonal distribution of the occluded, bioavailable and organic phosphorus fractions, in sediments of a polluted estuary (Botafogo river), and other considered as a background area (Carrapicho river), and determine the correlations between the concentration of phosphorus in sediments with the grain size, calcium carbonate, organic matter, dissolved phosphorus and salinity. No significant seasonal variation of phosphorus fractions concentrations was observed. The highest concentrations of occluded phosphorus was registered at Santa Cruz Channel sampling station with median value of 558,80 μg.g−1. In the Botafogo river estuary were found the highest concentrations of organic, and bioavailable phosphorus with median values of 209,19 μg.g−1 and 398,09 μg.g−1 respectively, due to the high content of fine sediments in this area. The organic matter content was positively correlated with the organic, bioavailable and occluded phosphorus fractions r2 = 0.9335; 0.8882; and 0.7750 respectively. The occluded phosphorus was the major fraction of the total phosphorus in the whole study site and showed a high correlation (r = 0.8218) with the percentage of CaCO3 in sediments, unlike the others phosphorus fractions with r < 0.6.Weak correlations between the phosphorus fractions and the dissolved phosphorus were found, the bioavailable phosphorus showed the higher correlation with the water column concentrations (r = 0,5362).
Gomes, V.J.C., Freitas, P.T.A., Asp, N.E., 2013. Dynamics and seasonality of the middle sector of a macrotidal estuary
This study presents the results on the hydrodynamic evaluation of the middle sector of the Caeté estuary (North Brazil), considering seasonal variations of rainfall and fluvial discharge, as well as neap-spring tidal cycle. Measuring campaigns were performed over 13 hours at spring and neap tides during 2011. There, cross-sectionally averaged current velocities and direction, water levels, salinity and SSC (suspended solid concentration) were monitored. The evaluated estuarine sector showed an asymmetric tidal pattern as expected, with higher current velocities during the ebb, although this tidal phase was persistently longer. The flood phase presented two discernible velocity peaks, especially during the spring tide, where the main peak occurs at the first half of the flood, as it flows landwards into the channel, and a secondary peak, as the large contiguous mangrove areas are flooded. Ebb currents were generally higher (e.g. 1.3 m.s−1 at spring/wet season) than during the flood (e.g. 1.1 m.s−1 at spring/wet season). The flood tidal currents surpass the ebb currents only during neap cycles at the dry season (0.74 m.s−1 at ebb and 0.78 m.s−1 at flood phase). The SSC could be directly related to the current velocities, therefore with the resuspension process. Nevertheless, SSC, as well as current velocities, were substantially higher at the spring tides, when the suspended sediment is effectively transported. During spring tides at the wet season SSC reached more than 3 g.L−1. Salinity variation within a tidal cycle was much higher during the spring tide (e.g. 22 at dry and 2 at wet season) than during the neap (e.g. 14 at dry and 0 at wet season), as well as at the dry season, in comparison with the dry season. This process would be the result of the seasonal longitudinal displacement of the mixing zone due to strong fluvial discharge variation. At the same time the mixing zone is also displaced according to the spring/neap variation. The same process would explain SSC variations, due to turbidity maximum zone migration in association with salinity, as SSC measurements suggest. Therefore, the presented results have showed the substantial relevancy of flood/ebb, spring/neap and wet/dry season variations for hydrology at this estuarine sector.
Leite, N.R., Magalhães, A., Palma, M.B., Flores Montes, M., Pereira, L.C.C. and Costa, R.M. da, 2013. Diel variation in the zooplankton of a highly dynamic Amazonian estuary. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1146–1151, ISSN 0749-0208.-->
The short-term dynamics (circadian and tidal cycles) of the zooplankton community were investigated in the Taperaçu estuary in northern Brazil. The plankton samples were collected in April (rainy season) at a fixed station, located in the middle sector of this estuary, through horizontal tows (plankton net with 200 μm mesh), every 3 hours over a 24-hour period, during the spring tide. Altogether, 51 zooplankton taxa were identified, of which the copepods Paracalanus quasimodo (34.6 to 13,852.8 ind.m−3; mean: 2,320.8±3,842.2 ind.m−3), Labidocera fluviatilis (2.0 to 3,209.2 ind.m−3; mean: 484.5±804.4 ind.m−3), Pseudodiaptomus marshi (9.7 to 1,599.6 ind.m−3; mean: 453.9±580.5 ind.m−3), and Acartia tonsa (27.6 to 3,953.6 ind.m−3; mean: 694.4±1,269.4 ind.m−3) were the dominant species. While no significant short-term variation was observed in hydrological or biological parameters, fluctuations related to tidal height were recorded in abiotic parameters and the density of the principal zooplankton taxa. The temporal variation in copepod populations tended to reflect that of total zooplankton abundance. Mean zooplankton density varied from 509.1 ind.m−3 (ebb tide, at 16:30 h) to 25,514.3 ind.m−3 (flood tide, at 10:30 h), with an overall mean of 5,872.1±8,286.4 ind.m−3. Oscillations in the density of P. quasimodo, L. fluviatilis, and P. marshi were influenced by the morphological and morphodynamic characteristics of the Taperaçu estuary, associated with the recruitment of individuals from the adjacent Caeté estuary, which constitutes an important factor determining the structure of the zooplankton community recorded in the present study.
Lima, N. G.B, Galvani, E., Falcão, R. M. and Cunha-Lignon, M., 2013. Air temperature and canopy cover of impacted and conserved mangrove ecosystems: a study of a subtropical estuary in Brazil. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The aim of this study was to analyze and compare the variation of air temperature between impacted and conserved mangrove areas by monitoring the microclimate and canopy cover of mangrove forests in the southern coast of São Paulo State, Brazil. Data were collected from September 2011 to August 2012 using meteorological towers installed below the canopy at a height of 2 m. Hemispherical photographs were processed to acquire the canopy opening and Leaf Area Index, which quantifies the area with leaves, trunks and branches. The mangrove vegetation structure was characterized in permanent plots located in conserved and impacted areas. All plants were identified and described. Evaluations of the temperature data using Pearson linear correlation, T Paired and Wilcoxon tests with a significance level of 5% indicated a 94% correlation with r = 0.973. The vegetation was dominated by Rhizophora mangle (red mangrove) in both areas. The conserved mangrove forest presented a continuous recruitment of red mangrove seedlings and saplings, whereas the impacted mangrove forest was characterized by mangrove associate species and aquatic macrophytes, indicating environmental alteration. The absolute maximum temperatures recorded in the impacted and conserved mangrove forests were 36.1°C and 35.6°C, respectively. Moreover, the minimum recorded temperatures in the impacted and conserved mangroves were 8.6°C and 9.7°C, respectively. These results indicate that the temperature amplitudes are lower in the conserved mangrove (25.9°C) than in the impacted mangrove (27.5°C) and that the conservation status of the mangrove canopy contributes to the temperature variation in this environment.
Lopes, C.L., Plecha, S., Silva, P.A., and Dias, J.M., 2013. Influence of morphological changes in a lagoon flooding extension: case study of Ria de Aveiro (Portugal) In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Coastal lagoons are interface zones where land, water and atmosphere interact in a dynamic balance that is constantly being changed by natural and human influence. The hydrodynamics and morphology of these coastal systems continuously adapt to changes in the forcing agents and show a complex interconnection. Worldwide studies show that tidal propagation is strongly dependent on local morphologic features. Attending to these concerns, the present study aims to assess the changes in flooding extension at Ria de Aveiro, as well as in the tidal prism, induced by local morphological modifications. The analysis of the topo-hydrography available for the Ria de Aveiro, comprising two general surveys carried out in 1987/88 and 2011 and two updates of the inlet bathymetry performed in 2001 and 2012, shows the deepening of the lagoon main channels and of the inlet evolving region. A flooding assessment of the lagoon margins and the determination of the tidal prism were performed applying the hydrodynamic model ELCIRC considering the four morphologic configurations described and different tidal conditions. The numerical results show the importance of lagoon morphological changes, which induce an increase of about 16% between 1987/88 and 2012 in the lagoon flooded area for spring tide. The new flooded regions correspond to the margins of S.Jacinto channel head and lagoon central areas. Additionally, the tidal prism results evidence a redistribution of the water volume flowing into the lagoon among their main channels during the period under analysis.
Magalhães, A., Nobre, D.S.B., Bessa, R.S.C., Pereira, L.C.C. and Costa, R.M. da, 2013. Diel variation in the biomass and productivity of Acartia tonsa (Copepoda: Calanoida) in a tropical estuary (Taperaçu, northern Brazil). In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Diel variation in the productivity of the copepods Acartia lilljeborgii and Acartia tonsa was investigated in the Taperaçu estuary in July (rainy season) and October (dry season), 2004. The estimated productivity of A. lilljeborgii (min-max: 3.932,385.41 mg C m−3 d−1; mean: 246.60 mg C m−3 d−1) and A. tonsa (min-max: 0.32–160.21 mg C m−3 d−1; mean: 16.99 mg C m−3 d−1) highlight the importance of their contribution to zooplankton production in the Taperaçu estuary. The absence of significant short-term variation in the productivity of A. lilljeborgii and A. tonsa in relation to the period of the day may be related to the combined effect of the shallow depth of the waters of this estuary and its strong tidal currents. These factors rendered the water column homogeneous, reducing the effect of the vertical migration of the zooplankton as a potential factor responsible for oscillations in the density of these organisms during the course of the day. The influence of tidal variation (flood/ebb) on the dynamics of these two species was also unclear in this study due to a number of morphological and morphodynamic characteristics of the estuary, such as the absence of any measurable fluvial discharge and the small catchment area, which resulted in an minor and infrequent inflow of freshwater into the estuary.
Mazzolari, A., Trigo-Teixeira, A., and Araújo, M.A.V.C., 2013. A multicriteria meshing method applied to a shallow water model. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
In this study a multi-criteria meshing method for a 2D shallow water model is tested for a domain encompassing several spatial and hydrodynamic scales, from the Western Atlantic Ocean shelf in front of the Iberian Peninsula to the Lima River (Portugal) and its estuary. For the mesh design, a series of scalar meshing criteria are identified from known physical factors of the relevant processes being studied, such as the bathymetry, the topographical length scales and the expected characteristics of the flow motion. Computational constraints are applied as well. Each criterion is expressed in terms of a node spacing function. The final node spacing function driving the meshing process is obtained by merging the requirements of the previously defined criteria. An advancing front mesh generator performs the discretization in a single, unstructured and well graded mesh, having element side lengths varying over three orders of magnitude (from tens of km to meters). A shallow water model application tests the generated mesh, where tide elevations and phases are imposed at the ocean boundary and freshwater inflow at the upstream boundary. The model validation shows a general good agreement between computed and observed water elevations, currents and the asymmetry of the tidal signal, with an underestimation of the high water levels for the most upstream station. The wet and dry process is reproduced realistically, as the position of the wetted front matches closely the submerged areas of time-referenced aerial images.
Bezerra, M.O.M.; Freitas, P.P.;Baltazar, L.R.S.; Rollnic, M., 2013. Estuarine processes in macro-tides of Amazon estuaries: A Study of Hydrodynamics and Hydrometeorology in the Marajo Bay (Pará-Brazilyn: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The work carried out a hydrodynamic and hydrologic characterization in the estuary of the Para River (Marajó Bay), near the Colares and Guaras Islands (pará, Brazil). The goal is to verify the behavior of the semi-diurnal macro-tide in large Amazon estuaries with an emphasis on hydrodynamic and hydrological characterization of the pará River estuary. The work proposed as targets; to investigate the hydrodynamics as to stream and water level, and the physicochemical variations of the water body. The studies were conducted in quadrature and consisted of measurements of streams, salinity, temperature and tidal range. The main results showed that the pará River estuary, as to the hydrological characteristics of the system, showed no significant variations in salinity throughout the water column in most profiles during the surveys. However, in Colares, there was an increase in the salinity over time, ranging from 3 to 5. On the Island of Guarás, the salinity was around 4 in the entire water column. The temperature in both, Colares and Guarás, did not vary, it was always 29°C. These results show that, even during the drought period, with low flow, the effect of river water is one of the main forces of circulation, and even more important than mixing processes generated by the tide. As to the hydrodynamic characteristics of the system, it was found that stream direction during sampling varied widely, and was usually followed by low speeds. Overall, the estuary shows circulation of a very mixed kind, being mainly controlled by river discharge and secondarily by the oscillations of the tide. It is important to continue studies in this region, because the estuarine processes in macro-tides of Amazon estuaries are complex and do not have characteristics in common with other macro-tides estuaries due to the great flows of rivers in the Amazon region.
Marília Borges Palma, Kelli Garbosa da Costa, André Magalhães, Manuel de Jesus Flores Montes, Luci Cajueiro Carneiro Pereira, Rauqrírio Marinho da Costa
Palma, M.B., Costa, K.G. da, Magalhães, A., Flores Montes, J., Pereira, L.C.C. and Costa, R.M. da, 2013. Zooplankton it gl spatial and temporal distribution in an equatorial estuary (Amazon littoral, Brazil). In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Few data are available on the zooplankton communities of the Amazonian littoral zone. Given this, the present study investigated the structure and spatial-temporal variation in these organisms in the Taperaçu estuary. Samples were taken at three different stations during neap flood tides in rainy and dry seasons. Samples were taken from the subsurface water with a plankton net coupled to a flowmeter. Additional water samples were collected from the sub-surface in order to determine the chlorophyll-a concentrations. Salinity and pH were measured in situ. The lowest salinity (3.25) was recorded in the innermost station in February (2011), favouring the development of a number of oligohaline species, such as Bosmina sp., Daphnia sp., and Diaphanossoma sp. The highest salinity recorded at this station was 27.88. A total of 68 taxa were identified. The copepods were the most important group. Oithona oswaldocruzi and Acartia lilljeborgii were the predominant species in the rainy and dry seasons, respectively. The highest mean zooplankton densities were recorded during the rainy season at the innermost station (4,459,354.58±7,666,682.09 ind.m−3). While the Taperaçu estuary was dominated by saline waters throughout the study period, both coastal and estuarine species were able to develop during the rainy season. A limited freshwater pulse was observed in the rainy season, when adjacent marshes fed into the estuary, indicating that salinity (influenced by rainfall rates) was the main factor controlling the composition and density of the local zooplankton community.
Portela, L.I., Ramos, S. and Trigo-Teixeira, A., 2013. Effect of salinity on the settling velocity of fine sediments of a harbour basin. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Salinity is known to increase the cohesion of clay minerals, and thus the flocculation of fine-grained sediments in suspension. However, the influence of salinity on the settling velocity of natural particles is often unclear, due to organic and biological aggregation and other controlling factors. This paper examines the effect of salinity on the settling velocity of fine sediments collected in a harbour basin in the Tagus estuary. The sediment sample consists of silt- and clay-sized particles (D10 = 2 μm; D50 = 9 μm; D90 = 37 μm). Quartz is the main constituent and illite the main clay mineral. The experiments were conducted in a 2.25-m high settling column, for a constant initial concentration of fine sediment (1.5 g l−1) and different salinity values (0, 5, 10, 15 and 30). During each experiment, samples were collected at 10 vertical levels and at 10 time instants. Settling velocities were calculated on the basis of the time- evolution of suspended sediment concentrations. At the start of the experiments, after cessation of turbulence, settling velocities increased in direct relation with the increase in salinity, the maximum values ranging between 0.3 mm s−1 under freshwater conditions and 0.9 mm s−1 for a salinity of 30. After 5 hours, the proportion of the initial sediment remaining in suspension was 45% under freshwater conditions and only about 10% for salinities between 10 and 30. Using the mass-weighted mean settling velocity to describe the deposition fluxes, it is concluded that settling increases by a factor of 6.5 between freshwater and marine conditions.
Rangel, C.M.A., Baptista Neto, J.A., Lima, L.G., Oliveira, P.S. 2013. Speciation of Phosphorus in an estuarine system inside Guanabara Bay, RJ - SE Brazil. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1194–1199, ISSN 0749-0208.-->
The Guanabara Bay, located in the metropolitan region of Rio de Janeiro, comprises an urbanized and industrialized area in Brazil, which over the past decades has undergone an intense degradation process caused by the eutrophication of river systems that surround this bay. This process occurs through anthropogenic activities developed within the watershed adjacent to this estuarine environment. This article investigates the controls on sediments phosphorus (P) speciation dynamics as a function of its fractionation into chemically defined operational pools along an estuarine system. This work analyzed a total of 10 variables samples of superficial sediments collected along a Mangue estuarine system inside Guanabara Bay, RJ – SE Brazil. Monitoring phosphorus in sediment dynamics in this area is important to control the influence of seasonality and anthropogenic activity in this nutrient impact. Through analysis of the sediment total phosphorus in this system, there was contamination by phosphorus in Mangue estuarine system. Regarding the phosphorus fractionation, the various form of P are influenced by human impacts, where the main chemical fraction, in the winter and summer, associated with Fe in a reducing environment, typical of polluted environments.
Reyes-Merlo, M.Á., Díez-Minguito, M., Ortega-Sánchez, M., Baquerizo A. and Losada, M.Á., 2013. On the relative influence of climate forcing agents on the saline intrusion in a well-mixed estuary: Medium-term Monte Carlo. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12 International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1200–1205, ISSN 0749-0208.-->
In this work we analyze the estuarine circulation and the dependence of the salt intrusion on the climate forcing agents in the Guadalquivir river estuary. The salt flux driving mechanisms are discussed. Exchange flow is identified and characterized by means of estimates of the effective vertical turbulent viscosity Nz, which decreases from 1.2·10−3 m2/s near the mouth to 3.3 · 10−4 m2/s in the middle reach of the estuary due to the decrease of the shear stress and to the longitudinal density gradient. Power-law relationships are obtained to assess the relative influence of the tidal current amplitude, river flow, and wind conditions at the inner shelf on the saline intrusion. It is found that the dependence of the salt intrusion on the river flow increases with the flow, and the gravitational circulation is greatly enhanced during the fluvially-dominated regime. The influence of tides increases after high discharges due to the reduction of the boundary shear stresses associated to the mud entrainment. Easterly winds favors the baroclinic circulation, increasing the injection of saltier water, which replaces the superficial, low-salinity water flushed out of the estuary. The obtained relationships are used to predict on a medium-term basis the effect of different management strategies on the saline intrusion, by means of Markov Chain Monte Carlo simulations. Results show that the mean intrusion length would increase about 8% under the expected scenario in which the freshwater discharges decrease by 15% the next 15 years.
Schindler, R.J., Bass, S.J. and Manning, A.J. Effects of non-cohesive particles on suspended particle characteristics in a partially flocculated estuary during spring tides. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
We present unique, in-situ data describing suspended particle populations in a meso-tidal estuary over the tidal cycle where the proportion of cohesive and non-cohesive sediment varies temporally. Simultaneous measurements of sediment concentration and hydrodynamics reveal that suspended particle characteristics are highly variable over the tidal cycle primarily due to the variable presence of non-cohesive sands, rather than changes in suspended particulate matter concentration (SPMC) and turbulent shear stress (τ). The particle distributions reveal that sand fractions appear in suspension throughout the tidal cycle as part of flocs and as individual grains. Non-cohesive or dense, consolidated mud fractions are sourced primarily from bedload under high τ, particularly during flood acceleration. However, the flood-deceleration phase experiences an influx of advected marine sands that increase suspended sand content despite declining velocity and turbulent shear stress. This generates bimodality in particle distributions and mean particle characteristics are misleading. Comparison with data collected at the turbidity maximum zone, beyond the extent of non-cohesive particles, shows that population size, settling velocity and density vary significantly between locations despite being <10 km apart. The implications of this spatial variation for our understanding of estuarine sediment transport are discussed.
Shaeri, S., Tomlinson, R.B., Etemad-Shahidi, A., Strauss, D. and Hunt, S., 2013. Field measurement for investigating the dynamics of Currumbin Creek entrances In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1212–1217, ISSN 0749-0208.-->
Currumbin Creek is a small tidal inlet in south-eastern Queensland, Australia. There is a long history of morphological changes, entrance stabilization works and maintenance dredging activities. Despite these activities an effective long-term management plan is yet to be implemented. A key component of the development of such a plan is a model of morphological change, and this paper addresses an investigation of the dynamics of the whole system. A field campaign carried out in March, 2011 and included measurement of nearshore wave regimes, tidal levels and currents inside the creek, and also drogue tracking in the inlet entrance. Wave data was collected over six weeks by ADCPs in water depth of about 7-8 m. Tidal current discharges were also measured by an ADCP over two tidal cycles of 14.4 (spring) and 15 (neap) hours. Water levels were recorded using a Valeport Water Level Recorder during the whole measuring period. The investigations show that the creek is mixed, but mostly flood dominated and therefore, there is a reasonable potential for sediment to rapidly infill the entrance and for the entrance to be dominated by natural bypassing. This study is part of a broader research project aiming to maintain longer, more durable and stable tidal-inlet entrance channels in Currumbin Creek. These findings will contribute to the design of alternative entrance geometry or maintenance strategies in the next phase.
Silva, E.M., Costa, M.F., Barletta, M., 2013. Small-scale water quality monitoring networks. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The monitoring of seawater physico-chemistry using automated buoys is well developed for large oceanic scales. Accessible and easy to handle small-scale monitoring buoys and land-based receivers are still missing in coastal water monitoring. River basins, reservoirs and estuaries are the most stressed aquatic environments as a result of their intensive use. These water bodies, and adjacent coastal waters, are priority candidates for continuous and reliable water quality monitoring. Environmental Agencies establish monitoring programs that involve water sampling and laboratorial analysis. Small-scale automated monitoring systems work with relatively low costs if simple materials and readily available technologies are used. We propose the development of a monitoring system that involves small plastic buoys/moorings with temperature and salinity probes, signal emitter/receptor devices, and Programmable Logic Controller (PLC) with wireless communication. The proposed technologies already exist, but need to be developed to work together in inhospitable environments as salt water and high temperatures. It is indicated for the continuous monitoring of shallow water bodies within coastal conservation units, municipal water reservoirs and even by environmental agencies in an upstream/downstream design to monitor water intake and effluents discharges from industries and water treatment plants. Private users may also be interested in installing the system if they are responsible for the maintenance of the water quality of coastal environments. Cheaper and efficient water quality monitoring is key to the building of meaningful time series that can be statistically treated to allow predictions of water quality changes.
Sottolichio, A., Hanquiez, V., Périnotto, H., Sabouraud, L. and Weber, O., 2013. Evaluation of the recent morphological evolution of the Gironde estuary through the use of some preliminary synthetic indicators. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Drastic evolution of the physical coastal environment are expected in the future under the effect of climate change. They make necessary to better understand the past morphology evolution, especially considering areas that are the habitat for some specific ecosystems. Moreover, because the context of the water framework directive (WFD), EU members need to generate indicators to evaluate the status of estuarine water masses. To satisfy these two obectives, the recent evolution of the Gironde estuary has been studied by the analysis of bathymetry with GIS. The Gironde is the largest estuary of western Europe, and one of the most turbid. In this study, the analysis extents from 1962 to 1994. Results show that the zone of maximum volume of deposited sediment has migrated continuously towards the upstream portion of the estuary, which is coherent with the decrease of summer river flow and the upstream shift of the turbidity maximum toward the riverine sections. In addition, zones with relative stable and unstable morphology were identified, showing rythmic distribution similarly to those previously recognized through the evolution over 160 years (1825-1984). This seems to be independent from the fluvial regime, but rather related to the interaction between tidal cooscillations and estuarine morphology, which is not elucidated yet. Finally, some hydro-morpho-sediemntary (HMS) indicators useful to the WFD have been described : distribution of depths, changes on cross section areas, changes of intertidal areas. They are discussed to discriminate the “natural” and “anthropogenic” contribution to morphological changes observed.
Souza Júnior, A.N., Magalhães, A., Pereira, L.C.C. and Costa, R.M. da, 2013. Zooplankton dynamics in a tropical Amazon estuary. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
While some data are available on plankton diversity in Amazonian coastal ecosystems, little is known about the seasonal variation in the zooplankton community of the Taperaçu estuary. In order to identify the zooplankton species in this estuary and to evaluate the relationship between these species and hydrological parameters, 48 samples were collected at a fixed station located in this estuary during rainy and dry season months. Salinity, temperature, pH, and dissolved oxygen varied significantly between seasons, and were directly influenced by rainfall. Chlorophyll a concentrations did not vary seasonally, although significant variation was recorded in nutrient concentrations. The zooplankton included seven phyla, of which the subclass Copepoda was the most diverse, with 17 species identified. Of these, the most important in terms of density and frequency were Pseudodiaptomus marshi, Oithona oswaldocruzi, Acartia lilljeborgii, Paracalanus quasimodo, Oithona hebes, Parvocalanus crassirostris, and Acartia tonsa. Fluctuations in diversity, evenness, and richness were associated with changes in salinity and density of the different taxa. A cluster analysis revealed the formation of two distinct groups, which were determined by rainfall patterns. Overall, the population structure of the zooplankton in the Taperaju estuary was influenced primarily by rainfall, which affected the salinity of the system, and secondarily by the strong local hydrodynamics (in particular tidal currents) and mixing processes, which in turn regulate the importation and exportation of species and the distribution of zooplankton organisms in the water.
Chao W., Aiyu Q., Peifang W., Jun H., 2013. Estuarine ecosystem health assessment based on the DPSIR framework: a case of the Yangtze Estuary, China In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
With population growth and regional economic development, the relationship between estuaries and human activities grows ever closer. Meanwhile, estuaries and adjacent coasts are facing serious threats from excess resource utilization and adverse environmental changes, making it both necessary and urgent to conduct studies on estuarine ecosystem health. This paper developed an approach using the Driver-Pressure-State change-Impact-Response (DPSIR) framework to evaluation of estuarine ecosystem state, causes of degradation and the legislative and management responses meant to improve conditions. Correlation analysis was used to analyze the linkage of indicators to avoid double counting of the aspects. Sensitivity analysis was also applied to analyze the small changes in indicator values resulting in changes of the integrated health value. The assessment results showed that the health state of the Yangtze Estuary ecosystem has been progressively declined since the late 1990s; and it reached the worst situation in the middle 2000s. The indicators of driver, pressure and impact systems showed the obvious sensitivity to the integrated health value. Due to the implementation of a series of ecological restoration measures, the estuary has shown some improvement trends in the late 2000s.
Yoon, B.I. and Woo, S.B., 2013. Tidal asymmetry and flood/ebb dominance around the Yeomha channel in the Han River Estuary, South Korea In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Several field measurements were conducted to study the characteristic of tidal asymmetry and flood/ebb dominance in the Han River Estuary (HRE), Gyeonggi Bay (GGB) on the western coast of Korea. Tidal currents at this area were simultaneously measured at four stations during the winter season, and previously observed tidal data were analyzed. The HRE is macro-tidal coastal zone with a mean depth less than 12m and a tidal range varying 3.5 (neap) to 8.0m (spring). The tidal amplitude to depth ratio is large enough to generate non-linearity in the tidal wave. The relative phases (2M2-M4) are represented flood dominant using harmonic constants from previously observed tidal data. However, there exists a limitation to apply this kind of method for tidal asymmetry to an area in which freshwater discharge is assumed to be relatively small. Statistical analysis of tidal current data in HRE indicated that ebb current is stronger than flood. Analysis of slack time of tidal current showed that ebb duration time is longer than flood. To find the mechanisms for the features of ebb dominance, a tidal curve was reconstructed the major component (M2), in combination with the shallow water component (M4). This tidal curve presented domination of flood current. However, these curves showed ebb dominance after incorporating the non-harmonic components that included ebb-directional flow, calculated from tidally-averaged current. The results show that the flood current is overcome by enhanced ebb directional effect, which occurs around the Yeomha channel in the HRE owing to the seaward effect of averaged flow. These ebb directional current could be produced by freshwater and nonlinear effects of long-term variation of sea surface slope due to estuary non-linearity.
Yoon, B.I. and Woo, S.B., 2013. Correlation between freshwater discharge and salinity intrusion in Han River Estuary, South Korea In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The salinity distributions of estuaries and tidal rivers exhibit unique characteristics due to the effects of various external forces, such as tides, freshwater discharge, wind, and topographic effects. The interpretation and understanding of the structure of salinity profiles in coastal and estuarine areas is necessary for addressing issues related to oceanography, water quality, ecology, and engineering. To identify the salinity distribution of Han River Estuary (HRE), South Korea the surface salinity of the southern and northern regions of Yeomha Channel were observed from May to June, 2007. Variations in the salinity were clearly correlated with long- and short-term tidal fluctuations. Furthermore, the salinity strongly decreased when additional freshwater was discharged relative to the dry period, and more than 25 days were required following a high-discharge period to restore the salinity to that of the normal flow conditions. The characteristics of the axial salinity distribution in the Yeomha Channel of the HRE were studied using data from the National Marine Monitoring Network of the National Fisheries Research and Development Institute, and the length of the salinity intrusion relative to the tidal range, the amount of freshwater discharge, and topographic effects were expressed using an empirical equation. A correlation between the saltwater intrusion limit at the HRE and the freshwater discharge rate was expressed using an empirical equation. Based on this simple analytical approach, we believe that the structural characteristics of the salinity distribution in estuaries and tidal rivers vary not only due to freshwater discharge and tidal mechanisms but also due to topographic effects.
Yu, Y., Zhang, H. and Lemckert, C., 2013. Seasonal variations of the salinity and turbidity in the Brisbane River estuary, Queensland, Australia. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The Brisbane River estuary, Queensland, Australia, is a vital ecological region and of importance for people who live nearby. The estuarine health status has been influenced by both marine and riverine conditions. The estuary experiences high turbidity and salinity throughout most of the year, however, little is known about the actual turbidity and salinity structures within it. This study examined ten-years of field data to investigate the seasonal variations in salinity and turbidity. The results revealed that the salinity at the Brisbane River mouth was estimated to be 31.7 and 32.8 ppt during wet and dry seasons, respectively. The surface longitudinal salinity then decreased along the estuary, with the highest decreasing rates of 0.7 and 0.6 ppt/km occurring within the mid-estuary. The average salinity flux was 8.19×104 and 8.25×104 ppt m3/s during the wet and dry seasons, respectively. The slight discrepancy of salinity fluxes between two seasons may be attributed to the lack of consideration of the other freshwater inflows to the estuary. The actual salinity flux through the estuary will therefore fall within the two estimated flux values. It was also found that the length of the turbidity maximum was approximately 35 km during wet season, which was three times as long as it is during the dry seasons. The values indicate the perceived, and actual, health of the estuary changes with season and location and thus care must be taken when interpreting ad-hoc measurements.
Zheng, J.H., Peng, Y.X., Zhang, C. and Ju, Y., 2013. Recent evolution of Jiuduansha Shoal in Yangtze Estuary and its corresponding to engineering projects. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The Jiuduansha Shoal is located in Yangtze Estuary of China and has attracted a lot of attentions with respect to its historical bathymetry evolution because it involves rich environmental resources. Based on the measured bathymetry data from 1997 to 2008, the digital elevation model of Jiuduansha Shoal was developed and used to analyze the recent shoal evolution. It is of particular interest to investigate its corresponding to engineering projects. Results show that from 1997 to 2008, the shoal area increased very slowly but the increasing rate gradually decreased, which is well correlated to the decreasing of sediment discharge due to dam construction at the upstream of Yangtze River. The deep- water navigation channel project in Yangtze Estuary has obvious effects on the nearby hydrodynamic condition and the morphology of the Jiuduansha Shoal. Remarkable deposition in north and erosion in south occurred at the middle and lower parts of the shoal. A 10.2 km long sand spit formed along the outer edge of the south jetty of the navigation channel project, which is due to both the jetty construction and the flow circulation in the North Passage.
Barboza, E.G., Rosa, M.L.C.C., Dillenburg, S.R and Tomazelli, L.J., 2013. Preservation potential of foredunes in the stratigraphic record. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Foredunes occur worldwide on shorelines, especially those which are wave-dominated and with moderate to high sediment supply. Pelotas Basin, located in southern Brazil, has a significant record of foredunes which are present on modern beaches as well as in the geological record. Many locations along the Holocene coastal plain of Pelotas Basin were investigated with a Ground Penetrating Radar (GPR). Foredunes are present in almost all the investigated areas. However some peculiarities were found along these areas. At some places it is still possible to see foredune morphology in the field. At these places GPR profiles show a convex ridge morphology preserved and its separation by concave, sometimes filled swales. At other sites foredunes are covered by transgressive dunes, the morphology is not preserved and erosive surfaces are found on the top of the unit. Along the progradational sectors, dip profiles show that even where foredunes have their morphology preserved, some erosive scarps are found at the seaward face. These patterns indicate that high frequency events lead to the erosion of foredunes. The combination of sedimentary budget with climatic events sets foredune preservation and its pattern. Where sedimentary budget is high, progradation occurs faster and foredunes are preserved. However, where the sedimentary budget is not very expressive, the progradation is slower and part of the foredune is destroyed forming transgressive dunes or sand sheets.
Cabrera-Vega, L.L., Cruz-Avero, N., Hernández-Calvento, L., Hernández-Cordero, A.I. and Fernández-Cabrera, E., 2013. Morphological changes in dunes as an indicator of anthropogenic interferences in arid dune fields. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Coastal dunes systems have been widely modified by human activities, especially in recent decades. Some of the changes have modified the aeolian landforms which characterize these environments. The dune systems of the Canary Islands can be considered as arid systems due to its temperature and rainfall levels. For this reason, the speed at which the geomorphologic process (natural or induced by human activities) occur are more significant than in dune systems located at either temperate or tropical regions. In this sense, the Canary Islands beach-dune systems are ideal for testing the effects of human activity on these environments. This work identifies major alterations, from the 60's, on three dune systems where the tourism activity has developed to a considerable extent: Maspalomas (Gran Canaria), Corralejo (Fuerteventura) and Famara (Lanzarote). To analyse these changes, historical and current aerial photographs and orthophotographs were used, as well as field work. Changes have been classified by the causes that induced them: I) urban development; II) beach equipment; III) beach users; IV) maintenance activities; V) a combination of some of these former causes. Results indicate that urban development is the main cause of the alteration of these dune fields. In Maspalomas and Famara less than 35% of their surfaces are free of human actions capable of producing morphological changes, while in Corralejo this percentage reaches 63%. In the analyzed period, the surface of the dune fields have been reduced, some of the existing dunes have been modified, and new morphologies (natural and artificial) have appeared. The latter process is mostly associated with mismanagement in these areas.
Delgado-Fernandez, I., Davidson-Arnott, R.D.A., Bauer, B.O., Walker, I.J. and Ollerhead, J., 2013. Evaluation of the optimal resolution for characterizing the effect of beach surface moisture derived from remote sensing on Aeolian transport and deposition. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
This paper explores new possibilities offered by moisture maps obtained from a remote sensing system to evaluate the effect of measuring moisture at different spatial resolutions. The data are derived from a moisture map generated from an image taken during an aeolian event on October 21, 2007 at Greenwich Dunes, Prince Edward Island National Park, Canada, using a camera mounted on a mast on the foredune crest at a height of about 14 m above the beach. Data from the original, fine resolution (0.05 m) moisture map was gradually aggregated through pixel coarsening. The simple method of local variance was used to identify the grid resolution at which changes in moisture were best depicted. Results indicate that the optimal spatial resolution at which most moisture variability was conveyed within a moisture map was 0.6-0.9 m, which suggests that finer resolutions do not necessarily provide the best representation of surface moisture that could be used in predictions of aeolian sediment transport.
El Mrini, A., Anthony, E.J.,Taaouati, M., Nachite, D. and Maanan, M., 2013. A note oncontrastingmorphodynamics of two beach systems with different backshores, Tetouan coast, northwest Morocco: the role of grain size and humanaltered dune morphology. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The Mediterranean coast of Tetouan, in Morroco, comprises headland-bound beach-dune systems bordering small coastal plains that have been considerably altered by socio-economic activities and coastal infrastructure essentially related to tourism development. To analyze the response of the beach-dune systems to high-energy winds and storms, three successive surveys covering storm and fair-weather conditions were conducted in February and March 2008 in two sites with contrasting grain-size and morphological characteristics. Ksar Rimal beach is characterized by coarse to very coarse sand and the finer-grained dunes on the backshore have been largely flattened, while Cabo Negro beach exhibits fine sand but the aeolian dunes associated with this beach are still partly intact. The results show that morphological changes are larger and faster on Ksar Rima beach (modally intermediate to reflective) than on Cabo Negro beach (modally intermediate to dissipative). The former beach has a greater tendency to erosion during storms but also shows rapid recovery expressed essentially through berm cut and fill. Mild aeolian accretion seaward of a recently constructed wall on the upper beach also occurred under the influence of strong offshore winds. The changes on Cabo Negro beach were relatively mild and were dominated by dune reworking. Sand transported from the dunes to the beach was reworked into a large swash bar, prelude to landward sand recycling towards the source dunes.
Farrell, E.J. and Sherman, D.J., 2013. Estimates of the Schmidt Number for vertical flux distributions of wind-blown sand. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
From studies of suspended sediments in water or dust in air it is recognized that the Rouse profile represents a theoretically sound, first approximation of characteristic sediment concentration gradients. Rouse (1938) combined the influence of grain size and shear velocity changes into a universal equation. The Rouse number relates sediment size (in the form of settling velocity, w0) to shear velocity, the von Kármán constant (0.4) and the Schmidt Number, typically assumed to be equal to 1.0 but with much larger values reported. The shape of the Rouse concentration profile is controlled by the Rouse number exponent. We applied the Rouse profile model to 14 vertical flux profiles of wind-blown sand measured during a field experiment in Jericoacoara, Brazil in 2008. These data were supplemented with 96 vertical flux profiles obtained from fourteen wind tunnel and field experiments reported in the literature, for a total of 110 profiles. The analyses show that the performance of the Rouse model is not sensitive to changes in the range of variability we can expect to observe in values of fall velocity, shear velocity and the von Kármán constant but is very sensitive to changes in the values of the Schmidt number. First, the Rouse model was applied to vertical flux profiles using the common Schmidt number value of 1.0 in the Rouse number exponent. The model performed poorly in predicting the shape and magnitude of the vertical flux distributions (38% and 18% of the observed transport rate in field and wind tunnels, respectively). Alternative values were derived by adapting the profiles to equivalent concentration Rouse-type ratios and obtaining the slope values of the fitted power functions. With this approach, in field and wind tunnel experiments, the values of the Schmidt number ranged from 4.46 - 19.10 and 0.68 - 23.24, respectively, and predicted, on average, 82% and 90% of the observed transport rate. We tested a third method that does not require measuring vertical flux profiles. We found a strong relationship between the Schmidt number and a shear velocity - fall velocity ratio (r2= 0.65), with values ranging from 6.11 – 14.80 and 0.86 – 17.83, for field and wind tunnel experiments, respectively. These modified values of the Rouse exponents also resulted in vertical profiles that predicted similar distributions to the observed flux data and provide good predictions of the total transport rates (86% and 81% in field and wind tunnels experiments, respectively). To our knowledge, these are the first values of the Schmidt number derived for aeolian sand transport and the first successful application of the Rouse model to vertical flux profiles of saltation.
Hesp, P.A., 2013. A 34 year record of foredune morphodynamics at Dark Point, NSW, Australia In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Incipient foredunes are formed by æolian deposition in plants on the backshore. They commonly evolve into established foredunes, and are present on many of the world's coasts, yet there are very few medium to long term studies on how they evolve and change over time. An incipient foredune suite has been monitored at Dark Point, NSW, Australia since 1978, providing a 34 year record of dune evolution and dynamics, and therefore representing one of the very few medium term foredune monitoring sites in the world.
The foredune was initiated by the growth of a zone of discrete pioneer plant species (principally Spinifex) on the backshore following the destructive 1974–75 storms. Over a period of 24 years, 5 separate incipient foredunes developed as sediment was gradually returned to the surfzone and beach, and the beach prograded 70m. Sometime after 1998, storms cut back the seawardmost foredune and former foredunes were reactivated landwards of the 1998 foredune. This study demonstrates (i) how incipient foredunes form by both discrete seedling development, and seawards rhizome extension over time, (ii) how ramp and terrace morphologies eventually evolve into ridges, (iii) rates of beach accretion following storm erosion and backshore response, (iv) how wave erosion drives morphological changes and evolutionary sequences on foredunes, (v) the relationships between backshore height, foredune development and sea levels, and (vi) indications for the initiation and evolution of so-called ‘beach ridges'.
Jackson, D.W.T., Cruz-Avero, N., Smyth, T.A.G., Hernández-Calvento, L., 2013. 3D airflow modelling and dune migration patterns in a mobile coastal dune field In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Mobility patterns within dune fields are driven by wind action, antecedent form and local conditions, which determine their temporal and spatial morphodynamics. This mobility can have considerable impact on human activity and infrastructure, as well as forming an important element of the sedimentary system. Understanding how dune fields migrate over time should form an essential part of future management. Although particularly important in arid and semi-arid locations due to their enhanced sand transport dynamics, research on these systems has received surprisingly limited attention, with studies largely focused on temperate and tropical examples.
Here, we utilise 3D airflow modelling, in-situ wind measurements and high resolution topographical measurement of surface features at an arid coastal dune field site in Gran Canaria, Spain. Using the Computational Dynamics (CFD) software OpenFOAM, air flow is simulated over a section of dunes along a northeast-southwest orientation, representing predominant local wind direction. A 3D surface was generated using a 1m resolution LiDAR survey (conducted 2006) to provide an accurate surface topography for CFD model runs. Output from the model provided information on surface airflow, allowing forcing winds to be located on top of the 3D surface. Using a 2008 LiDAR survey we compare the response of the dune field to that forcing and dune migration patterns. Modelled surface wind speed clearly corresponds to the resulting migration patterns of dune migration. Results show, for the first time at this resolution, that migration patterns and modelled wind flow provides useful information for arid dune studies in coastal regions.
Miot da Silva, G., Hesp, P., Keim, B., Martinho, C.T. and Ferligoj, Y., 2013. Changes in dunefield geomorphology and vegetation cover as a response to local and regional climate variations. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Published analyses of aerial photographs show a marked increase in vegetation cover of coastal transgressive dunefields along the Southern Brazilian Holocene Barrier around the late 1970s. This phenomenon is reflecting an increase in precipitation and a decrease in aeolian sediment transport. These climatic changes are associated with recurring high intensity El Niño events related to the 1976/1977 regime shift of the Pacific Decadal Oscillation (PDO).
Montreuil, A-L., Bullard, J.E., Chandler, J.H., 2013. Detecting seasonal variations in embryo dune morphology using a terrestrial laser scanner. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Coastal embryo dunes are rarely the focus of research efforts despite the fact that they are often precursors to the development of established coastal dune fields. The aim of this paper is to quantify morphological changes within an embryo dune field using a terrestrial laser scanner (TLS), with particular emphasis on determining how the number, height and orientation of dunes changes from season to season in relation to external forcing factors. The study site was located on the upper (> MHWS) section of a macrotidal beach on the north Lincolnshire coast (UK) where the wind regime includes both onshore and offshore components. Dune morphology was monitored approximately every three months over a period of 16 months (July 2009– October 2010) using TLS. The volume of sand within the embryo dune field ranged from a minimum of 12,622.54 m3 in January 2010 to a maximum of 13,263.17 m3 in June 2010. The majority of volume gain was a result of seaward accretion in response to onshore aeolian sediment supply as opposed to either a gain in height or an expansion of the dune field in an alongshore direction. Sediment volume was reduced in the embryo dune field as a result of two severe storm surge events that occurred during the winter months. The storm surges caused elongated areas of erosion between dunes, aligned with the dominant wind direction. Between October 2009 and January 2010 the volume of the dunes decreased by 315.49 m3 corresponding to a volumetric ratio of sand thickness of −0.026 m month−1. However, subsequent surveys show that the dunes then progressively recovered. This research demonstrates the potential of high resolution terrestrial laser scanning for identifying small-scale morphological changes in coastal dune fields, essential for relating detected change to evolutionary processes.
Moulton, M.A.B., Oliveira Filho, S.R., Rocha, T.B., Fernandez, G.B. 2013. Foredunes of Rio de Janeiro coast: genesis, structure and morphology. Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1319–1324, ISSN 0749-0208.-->
The formation of foredunes is one of the most important processes that occur during the evolution of the coastal sandy barriers, and can be observed along the coast of Rio de Janeiro State (Brazil) in both regressive, aggradational or transgressive barriers. The aim of this paper is to demonstrate the main processes of foredune development in areas with distinct patterns of coastal sand barriers along the Rio de Janeiro coast, subject to onshore and/or offshore winds. For this purpose we studied three areas in which foredunes present a representative morphology and show different types of coastal barrier. In each area, morphological aspects and foredune sedimentary structure where analyzed. Using total station and DGPS to generate 2D and 3D profiles, and a GPR antenna (400 MHz) to examine the sedimentary structure, an overall picture of the foredune formation process and the barrier type associated was made. The results showed that, foredunes developed on top of the regressive barrier (Atafona Beach) represent less than 2 m of sediment accumulated above the well-preserved beach ridges, suggesting that the main source of sediment supply comes from the river. In the aggradational barrier (Peró Beach) the intense aeolian transport (onshore winds) masks any sequence of beach signal, forming significant sequences of foredunes/blowouts (in this case sediment supply comes from the shoreface). The last area (Massambaba Beach), where winds blow offshore as result to the change of coastline orientation, we registered overwash deposits and occasionally foredune development on top of the transgressive barrier.
Plomaritis, T.A.,Puyana, I., Benavente, J. Rodríguez-Polo, S 2013. Is the grain size trend analysis useful for aeolian sediment transport? The case of Bolonia dune (SW Spain). In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Grain size trend analysis (GSTA) has been used in various marine environments for the study of sediment transport pathways with a range of results. However, its use in cases of aeolian transport has been limited, despite the fact that the transport mechanisms are very similar. The GSTA was applied to the dune field of Bolonia (SW Spain) located at the western extremity of headland controlled log spiral bay. The principal factors of the formation of the dune are the dominant easterly winds that are locally accelerated due to the topography of the strait of Gibraltar and the forest plantation that started in 1960, as a measure of retraining the sediment transport. In the present study a total of 80 sediment samples were collected on the dune on a 15×30m grid. At the same time, a detailed topographic survey of the dune was conducted using a RTK-DGPS. The granulometric analysis showed little textural variation of parameters on the dune and a tendency to better classification towards the dune crest. The results obtained show a mixed behaviour, with good estimation of the transport pathways at the foot of the dune and opposite pathway direction near the crest. The presence of secondary transversal dune forms and deflation zones has been identified as the main reason for the poor results of the GSTA over this area.
Sherman, D.J., Houser, C., Ellis, J.T., Farrell, E.J., Li, B., Davidson-Arnott, R.G.D., Baas, A.C.W., and Maia, L.P., 2013. Characterization of aeolian streamers using time-averaged videography. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Aeolian streamers are common in prototype saltation systems. Streamers are elongate, flow-aligned features within which the concentrations of saltating grains are large relative to a spanwise average concentration. The occurrence of streamers introduces substantial spatial and temporal variability in local sand transport rates. There have been few studies to attempt to characterize the scales of streamers, and the results of those studies have been constrained because they use Eulerian approaches to measure an inherently Lagrangian process. We describe the results from a field experiment designed to address this methodological problem. Field experiments were conducted at Jericoacoara, Ceará, Brazil, in October, 2011. The wind field was measured with ultrasonic anemometers and ruggedized thermal probes. Transport rates were measured using Miniphones, Wenglor Particle Counters, and hose traps. A set of three video cameras, deployed in a triangular array, was used to capture images of streamers. The field of vision for the central, upwind-facing camera was a minimum of about 15 m, expanding to more than 100 m in the middle distance. Video images were time-averaged over a number of intervals, ranging from 1 – 64 seconds, to establish characteristic path lengths and spatial and temporal scales. The results of these analyses show that this methodological approach is technically sound. Streamer characteristics are center-to-center spacings of about 1 m, length-scales exceeding 50 m and time scales of individual streamers exceeding 64 s.
Wakes, S., 2013. Three-dimensional Computational Fluid Dynamic experiments over complex dune topography In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
For modeling coastal dune systems the topography is often complex with complicating factors such as dune vegetation, sediment transport and the sand properties. Strategies such as simplifying the geometry and vegetation and no sediment transportation have been applied and provided insight into mechanisms of flow over the coastal dunes at Mason Bay, Stewart Island, New Zealand. Simulations building on the complexity of this modeling process are undertaken with a targeted mesh. Included was surface roughness signifying areas of vegetation but no Aeolian sediment transportation. Comparing preliminary results against the existing two and three-dimensional simulations and field data shows that although the strategy of splitting the domain in order to achieve three-dimensional results originally is workable simulating the whole domain is ideal. Grid adaption allows targeting of mesh in areas of most interest, mostly close to the dune surface and within the first 10m above the surface but needs to be done with care. There were distinct differences in wind velocity profile when comparing the results. It is also showed that the model choice has significance for turbulence parameters, with possible implications for sediment transportation, particularly at lower heights. In spite of the complex topography, the flow is strongly two-dimensional in some parts of the domain whilst strongly three dimensional in other areas. Therefore each level of simulation has a role in understanding the underlying flow mechanisms involved and what insight to the flow is required. Understanding gained from the previous work was invaluable in the extension to full three-dimensional simulations.
Azzopardi J., Deidun A., Gianni F., Gauci A. P., Angulo Pan, B. and Cioffi M., 2013. Classification of the coastal water bodies of the Maltese Islands through the assessment of decadal ocean colour data set
Nine coastal water bodies off the Maltese Islands (Central Mediterranean) were identified within the Water Framework Directive. The degree of spatial and seasonal variability in the ocean colour chlorophyll-a values (monthly re-analysed values originating from MODIS, MERIS and SeaWiFS sensors available from the MyOcean Marine Core Service) for these water bodies in the 2003–2011 period was evaluated graphically and statistically. Weekly values from the same satellite platforms were only available for the period 2010–2011 and these were analysed separately. The nine coastal water bodies were characterized by ocean colour values consistent with an oligotrophic water body, with seasonal mean values ranging from 0.06 to 0.35 mg/m3. The same nine coastal water bodies were classified according to an arbitrary ocean colour index based on seasonal mean values calculated over the entire 2003–2011 period.
The seasonal pattern of variability within ocean colour values across the different coastal water bodies over a single year was highly homogenous, with highest values being recorded during the December–February period, and lowest values being recorded during the May–August period, with very few exceptions (solely recorded in 2010 and 2011). Although statistical analyses (PERMANOVA) showed significant inter-annual differences between seasonal ocean colour values of the different water bodies, spatial variations among the same values were statistically significant only in the spring and summer seasons, over the entire nine-year period. However, the pairwise tests revealed that most of these significantly different comparisons were registered during the 2010–2011 summer seasons. These spatial differences could either be due to an artefact (the 2010 and 2011 ocean colour data sets were derived using a different chlorophyll-a algorithm and different satellites than the 2003–2009 ones) or else they could be real (e.g. some of the coastal water bodies exhibiting higher ocean colour values are optically more complex since they host large coastal embayments, intensive aquaculture activities, treated sewage discharges and other anthropogenic activities).
Cenci, L., Disperati, L., Sousa, L.P., Phillips, M. and Alves, F.L., 2013. Geomatics for Integrated Coastal Zone Management: multitemporal shoreline analysis and future regional perspective for the Portuguese Central Region. Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1349–1354, ISSN 0749-0208.-->
Shoreline mapping and change detection are critical for Integrated Coastal Zone Management (ICZM) and all that it represents. This research utilized previous studies that combined both Remote Sensing and Geographical Information System (GIS) techniques to assess, map and forecast shoreline evolution from short-term perspectives. The study area is located in the central region of Portugal, between the counties of Ovar and Marinha Grande (circa 140 km) and the time period assessed was from 1984 to 2011. Historical data were used to calculate advance and retreat rates in order to support environmental scenarios for the Portuguese Central Region's Coastal Management Plan. To ensure accuracy, a repeatable procedure was validated using Landsat TM and ETM satellite images, which were subsequently enhanced and elaborated by Remote Sensing analyses to detect and extract shorelines. They were subsequently integrated within an Esri ArcGIS software application (DSAS - Digital Shoreline Analysis System) to determine and predict rates of coastline change. Graphical DSAS plots identified coastline phases and shifts and were used to simulate the 2022 coastline scenario. These results will be integrated into the Coastal Zone Management Plan (Horizon – 2022). Importantly this methodological planning approach provides visual coastline change information for regional decision-makers and stakeholders.
Cho, D., Han, K., 2013. Feasibility Study of Structural Behavior Monitoring with GPS and Accelerometer
Coastal structures could be damaged or even collapsed by abnormal ultimate loadings because they are exposed to the extreme natural environmental conditions such as strong winds, earthquakes, and tsunamis, etc. Due to these loadings, they need to be evaluated through a health monitoring continuously. As the displacement of the structures can represent structural behaviors, precise measurement for the displacement of the structures in order to assess reliably the state of the structures is required. In this study, problems of RTK (Real Time Kinematic)-GPS (Global Positioning System) and an accelerometer sensor when applied to structures were experimentally identified through a comparison between results from the experiments. In order to compare the displacements precisely, a steel cantilever beam was fabricated and a variety of displacements by loadings was measured. An integrated displacement was calculated by the improved RTK-GPS and accelerometer on the frequency of observation and positioning accuracy. This integrated displacement was also compared with that of LVDT (Linear variable differential transformer) to check the validity of application and feasibility. Positioning data from the RTK-GPS and the data from the accelerometer sensor were integrated by using extracting substitution displacements. Long and short period displacements were extracted from the RTK-GPS positioning data and the accelerometer positioning data respectively. The maximum and minimum error and average error were calculated for each case to determine whether some degree of accuracy of the data. The integration method with a RTK-GPS and an accelerometer could replace the LVDT when it is difficult to apply LVDT to the field. And also this method is expected to be used for the long-term health monitoring in real-time by measuring global behaviors and local dynamic displacements of the coastal structures.
Cho, J. M., Lee, D. H., Lee, M. R., Cho, J. H., Yun, H. S., Jeong, T. J., Jang, A. and Kim, T. Y., 2013. Comparison of Geostrophic Current Estimation around the Korean Peninsula from Remote Sensing-based MSS models
Altimetry satellites like Geosat, ERS-1/2, Envisat and Topex-Poseidon, which have been developed and deployed since the 1970s, have collected immense arrays of data on the sea, and the data thus gathered have been used in oceanography as well as in a variety of scientific disciplines, such as geophysics and geodesy. The mean dynamic ocean topography or Sea Surface Topography (SST), obtained by calculating the difference between the Mean Sea Surface (MSS) and the geoid surface, plays a critical role in determining the earth's shape and geoid as well as in the precision modeling of the earth's gravity field, ocean currents, and tidal waves. In the study, the MSS_CNES_CLS10 (Centre National d'Etudes Spatiales Collectre Localisation Satellites 2010) and DTU10MSS (Danmarks Tekniske Universitet 2010) MSS models calculated with the data obtained by a number of altimetry and gravity observation satellites, such as Topex/Poseidon, CHAMP, and GRACE, as well as a geoid model calculated from the EGM2008 gravity field model, were employed to determine the SST around the Korean Peninsula and to calculate its geostrophic current, the key source of the sea surface current. The SST and geostrophic current were also calculated using the MSS_CNES_CLS10 and DTU10MSS MSS model calculated from the satellite data, as well as a geoid model calculated from the EGM2008 earth's gravity field model, with a maximum degree and order 20 In the study, comparing calculated velocity with measured data and previous researches, calculated velocity of current is as 2 to 4 times faster than measured velocity at the East Sea which changes depth rapidly. However, it is similar to velocity and direction at over 40km far from the coastal area and the Yellow Sea which changes depth gradually. Also, as a result of comparison with two MSS models, MSS_CNES_CLS10 model is more accurate than DTU10MSS model, but the difference was trivial. If it is possible to estimate the movement of oceanic current which are affected by wind, pressure, density, tides and temperature of ocean, and add onto method of estimating geostrophic current used in this research, we will be able to estimate in more detail at the oceanic current. This study would provide some useful data for maritime voyage and fishery.
Choi, J. K., Hyun Yang, H. J. Han, Ryu, J. H. and Park, Y.J., 2013. Quantitative estimation of the suspended sediment movements in the coastal region using GOCI
The Geostationary Ocean Color Imager (GOCI), the world's first geostationary ocean color observation satellite, is useful for monitoring the temporal dynamics of coastal water turbidity because it can obtain satellite images every hour during the daytime. Temporal variation in turbidity is the key to understanding sediment dynamics in coastal regions. For example, a certain patch of suspended sediment in surface water can be traced every hour by generating a GOCI- derived map of suspended sediment concentration (SSC). By calculating the variations in the position of the patch every hour quantitatively, we can obtain information on the current movement in the region quantitatively. Here, we investigate the applicability of GOCI data to monitoring of the temporal movement of suspended sediment in coastal areas and to the development of algorithms for calculating the current speed and direction. Our study was performed in areas near Gyeonggi Bay on the mid-west coast of the Korean Peninsula. Field work was performed to obtain in situ measurements of SSC and optical properties of the water surface. These data could then be combined to derive an SSC algorithm based on the relationship between the SSC and remote sensing reflectance (Rrs) values. We calculated the suspended sediment movement from hourly SSC images. Current velocity and direction were also measured in the field to validate and identify the calculated movement. GOCI images acquired on the same day as the samples were used to generate a map of turbidity and to estimate the differences in SSC displayed in each image. We found that GOCI could be effectively used to monitor the temporal dynamics of the turbidity of coastal waters, i.e., sediment movements driven by currents along the west coast of the Korean Peninsula. Sediment movements can be applied to develop GOCI-based algorithms that calculate current velocities and generate maps of current vectors in this coastal area.
Eom, J., Choi, J.K.., Lee, Y.K., Ryu, J.H., Won, J.S., 2013. Standardization of sedimentary facies and topography based on the tidal channel type in Western coastal area, Korea
The tidal flat area along the west coast of the Korean Peninsula is among the largest in the world. The Ganghwa-do tidal flat, which is an open type, the Geunso-bay tidal flat, which is a semi-closed bay, and the Hwang-do tidal flat in Cheonsu Bay have different benthic environments, formed by different surface sedimentary facies and topographic features. These benthic environments in each tidal flat are influenced mainly by the tidal channel network. In other words, knowledge of the tidal channel distribution pattern is a key for understanding the geophysical and surface-sedimentary facies. From a quantitative estimate of the tidal channel distribution pattern, it is possible to estimate the surface sedimentary facies and topographical features. In this study, we standardized the surface sedimentary facies and topography by developing a tidal flat index in terms of the tidal channel distribution pattern. To extract tidal channel data in the study area, we used remotely sensed data, such as those from the Korea Multi-Purpose Satellite-2 (KOMPSAT-2), Landsat Enhanced Thematic Mapper Plus (ETM ), and aerial photographs. In addition, we generated a digital elevation model (DEM) using the waterline method to standardize the topographic features. Surface sedimentary facies maps were generated based on field data using an interpolation method. From these data, we calculated the tidal channel index by a fractal method. We also analyzed the spatial correlation of the tidal channel index with surface sedimentary facies and topography, respectively, using a GIS tool. Low values of the tidal channel index, which indicated a simple pattern of tidal channel distribution, were identified at areas having low elevation and coarse-grained sediments. By contrast, high values of the tidal channel index, which indicated a dendritic pattern of tidal channel distribution, were identified at areas having high elevation and fine-grained sediments.
Frias, P., Horta, J., Almeida, L.P., Pacheco, A., Ferreira, Ó., 2013. Development of a WebGIS tool to determine tidal inlet evolution. In: Conley,D.C., Masselink, G., Russel, P.E.and O'Hare, T. J. (eds.)
Research into the consequences of engineering works on the long-term behaviour of inlet systems has been hindered by the absence of suitable datasets, the shortcomings of existing formulae and evaluation tools. Cross-sectional channel areas adjust to hydrodynamics and sediment transport conditions. The impacts of a new inlet on the adjacent shoreline can be unpredictable and are difficult to quantify. This paper presents the development of a Web GIS tool (WebInletAnalyst) that allows any coastal or hydraulic engineer to autonomous extract the evolution of key tidal inlet parameters such as minimum cross-section area, inlet width, maximum depth and migration distance, from a set of bathymetric charts and raw data surveys. The tool is built on a web interface written and compiled using source codes. The tool was applied to a test case (Ancão Inlet, Ria Formosa, Portugal) using available datasets and compared with results from other studies, following the Coastal Engineering Manual guidelines. Overall results showed that mean differences between manual and automate techniques were small and randomly distributed. The user' definition of the location and orientation of minimum cross-section profile affects the accuracy of the tool. Further improvements on the available web interface tool are being tested to allow a magnified view of the inlet channel area and a better precision on sketching the minimum cross-section profile. The tool will be ultimately made available on Python code, allowing future further improvements and adaptations by the scientific community.
Jong-Gyu Han and Seong-Pil Kim, 2013. Spatial Zonation of Storm Surge Hazardous Area in the Nakdong Estuary of Korea using High Precision Terrain Data Acquired with Airborne LiDAR System and Geospatial Analysis.
In this study, we estimated hazardous area vulnerable to storm surge and also investigated the areal increases under sea level rise condition. For quantitative assessment together with geospatial analysis with GIS we used precise one-meter-gridded airborne LiDAR-based topographical models, the relative vertical accuracies of which fall within ca. 30 cm excluding outliers. According to the inundation prediction the storm surge hazardous area is predicted to range approximately from 6 to 20 km2 depending on the storm power. The result shows also that in the higher sea level condition in 2100 the areal extent could be increased by up to 68 %. Being noteworthy the areal increase was greater in the small-scale storms than in the large. The elevation models and cross-sectional profiles of the barrier islands protecting the Nakdong estuary were acquired for further assessment and discussion on their roles of natural underwater dykes. As larger inundation potential could be transferred into greater socioeconomic damages, the authors expect that precise quantitative estimation of vulnerability could be used for efficient and rational information for long-term coastal management planning.
Holman, R.A. and Stanley, J., 2013. cBathy Estimation in the Mixed Wave-Current Domain of a Tidal Estuary.
The last decade has seen considerable progress in the development of algorithms for nearshore bathymetry estimation based on celerity observations of ocean surface waves. This work has evolved into a robust algorithm called cBathy which produces operational results that compared well to 16 CRAB surveys at Duck, NC, collected over two years (bias 0.19 m, rmse 0.51 m over a 1000 by 500 analysis region). However, cBathy is presently based on a wave dispersion implementation that neglects the effects of currents. In May 2012, cBathy was tested in a tidal inlet environment at the RIVET experiment at New River Inlet, NC, a location with a complex ebb tidal delta and strong tidal currents. Initial analyses without Doppler correction to the algorithm show up to 50% overestimation of depth excursions at tidal time scales, presumably associated with wave-current effects. Data from in situ instruments at the RIVET experiment are used to test the adjustments to the algorithm needed for Doppler shifting and found to explain some, but not all, of the bias. The algorithm also estimates dominant wavelengths and wave directions associated with a suite of incident wave frequencies. Both the dominant frequencies and wave directions were found to vary systematically through the tide as the changing water depths alter dissipation and refraction patterns over the shoals.
Horta, J., Moura, D., Gabriel, S., Ferreira, Ó., 2013. Measurement of pocket beach morphology using geographic information technology: the MAPBeach toolbox
The measurement and evaluation of the morphological response of a beach to changes on wave conditions has been the subject of several studies over the past years. This paper presents and discusses a methodology to compute variations in pocket beaches after morphological monitoring performed trough topographical surveys. The GIS toolbox MAPBeach – GIS tools for Morphological Analysis at Pocket Beaches – was developed to simplify the morphological analysis of pocket beaches. The methodology was applied and tested at two beaches (Galé and Olhos de Água, Algarve, Portugal) with different exposition to the predominant swell. The morphological monitoring used the Global Navigation Satellite System (GNSS) and was performed with relative positioning in real time kinematic (RTK) mode. The obtained data were compiled and used to produce digital terrain models in a Geographic Information System (GIS) environment. The developed GIS toolbox enabled a quick and efficient evaluation of the morphological changes occurred at the selected beaches, associated to different forcing conditions, through the determination and further analysis of a set of pre-defined morphological parameters, including beach profiles, beach slope, elevation, volumes, beach curvature, beach rotation, among others. The developed tools proved to be robust and easy to operate, facilitating both the scientific analysis as the determination of useful parameters for coastal management, being therefore of broad application.
Hwang, J.S, Yun, H.S., Kang, I.G., Choi, Y.S., Lee, D.H. and Hong, S.
For this study, a system capable of measuring the absolute position and shape of nearby rocks that cover and uncover along the shore precisely and remotely was devised. The system, consisting of a GPS/INS and a stereo digital camera, can be attached to the side of a ship. A surveying ship equipped with the system may sail around the rocks, obtaining GPS and INS data on the rocks, and digital images captured with a stereo cameras. The data can then be post-processed to obtain precise 3D spatial information on the rocks. The key methods used to realize the system was GPS/INS integration method, real-time direct geo-referencing method for a digital camera, and 3D scanning technology that automatically matches stereo images. Among these methods, the stereo image matching method was developed for this study. The method was realized by combining the conventional SURF descriptor generation algorithm, the matching methods using the scanning area reduction method based on the epipolar geometric theory, and matching line-based filtering, thus allowing faster and more accurate image matching and 3D surveying on the rocks. To verify the feasibility of the technology, a test survey was conducted on a rock and a dyke near Incheon, South Korea. The test run showed that the system could obtain 3D spatial data on the rocks with an average 10.45 cm planar and 14.32 cm elevation errors.
KEYWORDS: Geostationary Ocean Color Imager (GOCI), cloud-free image, hourly varying image data, ROMS operational mode, convergence of satellite data with model data
Kim, C.S., Park, Y.J., Park, K.S., Shim, J.S. and Lim, H.S., 2013. Application of GOCI Satellite Data to Ocean Modeling
This study demonstrates possible application of satellite data to numerical modeling, and vice versa, to improve the quality of the processed information. A new geostationary satellite with the three missions of communication, ocean and meteorology was launched in June 2010. The ocean mission part, GOCI (The geostationary Ocean Color Imager), is now in data service of ocean color images at every hour during daytime with a spatial resolution of 500 m. The scanned data covers the north Pacific with focusing on Korean Peninsula and adjacent seas. Using the optical sensors, the GOCI images usually contain the cloud-blocked zone. We investigate a method to acquire the cloud-free images of environment information by using the operational 3-D ocean model, the ROMS. The clear-image data are used as boundary condition to the numerical modeling, and then the model results are used to recover the cloud-covered area. The hourly varying image data are also excellent data for the ocean numerical modeling in terms of temporal and spatial variation of the ocean environment. By close examination of hourly producing images from GOCI, the temporal variation is very useful for operational purpose along with the three-dimensional ocean model such as ROMS. Being in operational mode, the ROMS ocean model produces temporal and structural variation of coastal features by using the compatible GOCI data, or the GOCI images can be improved by using the model results for cloud-free images. This study shows some excellent test cases on various coastal phenomena, such as a river plume of highly turbid waters, coastal upwelling, transport of algal bloom, typhoon tracking and the distribution of surface suspended sediment concentration. A method for the convergence of GOCI data and ocean model results has been introduced. The clouding network system for the convergence of satellite data and ocean model data is a promising method that combines two different media, thus yielding dynamically validated products.
Kim, I.H., Lee, H.S. and Song, D.S., 2013. Time series analysis of shoreline changes in Gonghyunjin and Songjiho Beaches, South Korea using aerial photographs and remotely sensed imagery
Given the speed and pervasiveness of anthropogenic landcover changes, especially in coastal areas, monitoring shoreline alterations and their impacts is critical for intelligent coastal development and beach use management. In this study, we describe a monitoring and analysis framework that uses aerial photography, remotely sensed imagery, and field surveys to detect changes in beach width and area along Gonghyunjin and Songjiho Beaches in South Korea. We used IKONOS imagery acquired in 2004; aerial photographs captured in 1991, 2005, 2009 and 2010; and field surveys conducted in 2010 and 2011. Based on comparisons of these data sources, we detected widespread erosion on both beaches starting in 2004, resulting in 12% reduction in the plane area of these beaches between 2004 and 2010. Most dramatically, we noted that beach width eroded by 28.5 m at the point 700 m south of Gonghyunjin Harbor, and similar declines occurred at several other locations. Erosion occurred at these locations because extended breakwaters in the Gonghyunjin Harbor either blocked or interrupted drift sand transport processes, causing sand to be carried away from some locations without accretion to replenish it. In addition, according to field surveys, we determined that erosion and accretion processes continued to vary seasonally in 2010 and 2011, resulting in smaller overall changes than those in the study years prior to 2010. However, we suggest that severe erosion may occur in the future at some locations if sand continues to be transported north onto Songjiho Beach without replenishment. Thus, we demonstrated that the construction of artificial structures around the harbor caused changes along the shoreline. Our monitoring framework has important applications for future observation of anthropogenically driven changes to this coastal area and serves as an applicable tool in other coastal regions worldwide.
Gonéri Le Cozannet, Ahmed Ait-Kaci, Sébastien Colas, Xavier De Lacaze, Sophie Lecacheux, Carola Mirgon, Cédric Peinturier, Manuel Garcin, Carlos Oliveros
Le Cozannet, G., Ait-Kaci, H., Colas, S., De Lacaze, X., Lecacheux, S., Mirgon, C., Peinturier, C., Garcin, M., and Oliveros, C., 2013. Recent GIS based national assessments of climate change consequences in France: methods, results and lessons learnt
This paper reviews two recent assessments undertaken in France for evaluating national scale consequences of global change for coastal hazards and risks, namely marine submersion and coastal erosion. In a first approach, the potential consequences of climate change were evaluated in a direct quantitative way, however with high uncertainties in the final evaluation. Recognizing that uncertainties could hardly be reduced, a second assessment based on a multi-criteria evaluation was then undertaken. Geomorphological and marine factors that account for physical vulnerability to coastal hazards were evaluated for 21 coastal entities in metropolitan France. The evaluation was structured using the analytical hierarchy process (AHP). The results highlighted the fact that in some specific regions such as Languedoc-Roussillon (Mediterranean coast) and Pertuis (Atlantic coast), the population is expected to increase more than the mean average, while the coastal zone are also likely to be more strongly affected by coastal hazards. While such national scale evaluations in highly diversified coastal environments are still arguable, they may help identifying unsustainability in current trends and help defining priorities for future adaptation strategies.
Lee, D.H., Yun, H.S., Jung, H.I., Cho, J.M.., Cho, J.H., Jung, W.C. and Hwang, J.S., 2013. Transformation of Vertical Datum Surface in the Coastal Area using Hybrid Geoid Models
The national height system (NHS) of Korea is currently separated into land and sea, which makes it difficult to acquire homogenous and accurate height information throughout the nation. The NHS for land is defined by a bench-mark (BM) based on the mean sea level (MSL) of Incheon bay, which is managed by the National Geographic Information Institution (NGII), and that for seas is defined by the tidal bench-mark (TBM) based on the local MSL, which is managed by the Korea Hydrographic and Oceanographic Administration (KHOA). This is because these two institutions have different agendas in the use of height data. Therefore, once the differences between the vertical datum surfaces (VDS) on land and sea are considered, such differences could be converted into height information that is measured with different VDS. This study was conducted to homogenize height information for land and sea using the differences between hybrid geoid models fitted to the VDSs for land and sea and to develop a VDS transformation model that allows accurate transformation, with which to continuously and effectively unify the separated NHS throughout the whole area in Korea. For a precise hybrid geoid model, a precise gravimetric geoid model was first developed using the remove and restore (R-R) technique, based on all available gravity observations. Next, the differences between the height results based on each VDS of land and sea using 70 TBMs that had both results were compared and analyzed, and the geometric geoid height of TBM was calculated based on the VDS of land and sea through the precise GPS observations for 4 or more hours. Finally, the gravimetric geoid model was fitted to the acquired geometric geoid heights of TBMs to develop two hybrid geoid models, each of which is based on the VDS of land or sea, and to determine the differences between the two models as the VDS transformation model. The VDS transformation accuracy based on this model was approximately ±3 cm. It is expected that the results of this study can help minimize not only the confusion in the use of land and sea spatial information due to the disagreement between the two NHSs in Korea, but also the economic and time losses in the execution of coastal development and disaster prevention projects in the future.
Mole, M.A., Mortlock, T.R.C., Turner, I.L., Goodwin, I.D., Splinter, K.S. and Short, A.D., 2013. Capitalizing on the surfcam phenomenon: a pilot study in regional-scale shoreline and inshore wave monitoring utilizing existing camera infrastructure.
Driven by dynamic inshore wave climates, sandy beaches oscillate around long term mean trends at daily (storm events) to inter-annual timescales (regional climate cycles). Coastal imaging technology provides a practical means for sustained, autonomous beach morphology and inshore wave monitoring at high temporal resolution. However, existing, scientifically-proven systems are limited in their application due to cost and required infrastructure. A potential alternative has been identified in the existing surfcam networks operating at 100 sites around Australia and many sites around the world. This work reports a critical evaluation of this new, low-cost monitoring method which has the potential to significantly expand spatial coverage of coastal behavior; capturing both real-time forcing (waves) and effect (shoreline change). In this study, seven embayed beaches in New South Wales, Australia, are used to examine the potential for a sustainable regional monitoring network using existing surfcam infrastructure to provide daily measurements of shoreline position and inshore waves at the break point. Surfcam image-derived shorelines are compared at daily frequency over 10 months at one site to co-located Argus image-derived shorelines and at monthly frequency over 18 months at nine camera sites to concurrent on-ground RTK-GPS surveys. Preliminary comparisons to Argus image-derived and RTK-GPS surveyed shorelines indicated promising qualitative agreement. A simple geometric correction was shown to significantly improve the surfcam-derived shoreline measurements. Surfcam-derived inshore wave heights and periods are compared to three months of concurrent hourly nearshore (depth ~10m) wave buoy measurements at two camera sites. Initial evaluation of the wave measurement capability suggests a consistent over-estimation of smaller waves and under-estimation of larger waves. It is suggested that these “bottom-heavy” measurements are due to pixel rectification error associated with obliquity from a single low-angle camera; and the high variability in measurements due to beach and wave type.
Sobral, F.N.C., Pereira, P.S., Cavalcanti, P.G., Guedes, R.M.C., Calliari, L.J., 2013. Intertidal Bathymetry Estimation Using Video Images on a Dissipative Beach.
Located at southern of Brazil, Cassino beach is a multiple sandbar beach. A video technique to map intertidal bathymetry changes was applied using CMYK color model to find the waterline position, hydrodynamic data and runup 2% (R2) parameterizations. Linear regression between waterline video detected and elevation estimated with in situ measured maximum swash, showed a correlation coefficient of r2=0.82 and r2=0.91, respectively. Rmse values for those comparison was 10.14 m (horizontal detection) and 0.12 m (elevation). The empirical swash coefficient (Kosc) was 1.08 with a total error δz of rms=0.25 m and represents a waterline underestimated to compensate the overestimated horizontal determination. The principal error was found to be at horizontal position, which means that the R2 parameterization was efficient. The estimated bathymetry temporal evolution changes showed a similar morphologic evolution when compared with beach profile with a total rmse of 0.13 m.
Song, D.S., Kim, I.H. and Lee, H.S., 2013. Preliminary study of 3D Assessment of Coastal Erosion by Data Integration between Airborne LiDAR and DGPS Field Observations
The airborne Light Detection And Ranging (LiDAR) system has been allowed in monitoring various natural hazards, so highly accurate and airborne LiDAR data have been used in the field of oceanic sciences, including a digital terrain modeling and bathymetric mapping. In this study, we adopted airborne LiDAR measurements to assess coastal erosion for the first time. The airborne LiDAR data were acquired along the east coastal zone of Korea (shoreline is about 205km). The 3D topographical data and digital orthophotos, which were obtained from aerial LiDAR with a digital camera, were integrated with the beach profiles conducted by the VRS-based DGPS surveying. The integrated dataset were relocated into a developed flight simulator module, which is a Dynamic geographical information system solution with Digital AirScape (D-DAS), for the 3D visual analysis of erosion status. The 3D visual result of seasonal and yearly variability with respect to beach width is validated to understand the evolution trends of the coastal environment on the test areas. Preliminary result from this study shows the potential availability of LiDAR data and the additional opportunities within the 3 dimensional monitoring of coastal evolution, for a detailed evaluation of erosion supported by the Coastal Erosion Monitoring Program (CEMP). Additionally, we expect that the early introduction of the airborne LiDAR Bathymetry (ALB) system in Korea, such as Scanning Hydrographic Operational Airborne Lidar Survey (SHOALS), will be used for more effective and deliberative monitoring of coastal erosion in the coastal zone management program.
Yoo, J., Choi, J.-Y., Yoon, J.-J., Jun, K.-C., Shim, J.-S. Kim, S. and Min, I.-K., 2013. Measurements of wave runup over breakwater observed in field using optical imagery.
In this paper, wave run-up on the seaward slope of a breakwater in field was measured remotely using optical video imagery and investigated through comparisons with an empirical formula. In order to extract properties of wave run-up and over-topping on the breakwater slope from field videos, individual image frames were sequentially sampled at 3 Hz from a video burst first. Then, the sampled sequential image frames were rectified into real world coordinates. A crossshore image timestack was generated by collecting an image pixel array, which was defined along the cross-shore transect on the seaward breakwater face of interest. Trajectory of the run-up on the seaward face evolving in time was extracted from the image timestack using a line detection method. The properties of the run-up estimated from field video bursts were combined to the measurements of incident waves, in order to derive an empirical relation between incident waves and run-up. The video-based relative wave run-up height (i.e. Ru,2% / Hs) at a typical armored breakwater with tetrapods was found to be about 2.15. This value is about in the range of the general formula, which was derived from laboratory experiments in earlier studies.
Altomare, C., Gentile, G.M., 2013. An innovative methodology for the re-naturalization process of a shingle beach
The gravel beach of Torre del Porto (Italy) was affected by a huge erosive phenomenon during the last 30 years. The causes which led to the erosion and the design lines through which to obtain the re-naturalization have been identified. Following a new methodological approach, the project consisted of entrusting assorted rubble stones with a proper weight to the area. Consequently the natural formation process can unfold again its effectiveness and the beach is recreated. The monitoring of the sediment transport was essential to provide the information about the correct results of prediction and analysis of the nourishment. The methodology, results and monitoring phases are described in this paper.
Ellis, J.T. and Cappietti, L., 2013. Storm-driven hydrodynamic and sedimentological impacts to an engineered coast.
We replicated a breakwater, seawall, and artificial gravel beach from Marina di Pisa, Italy in a 1:40 scale-model. The model was tested in a wave-current flume that is 50 m long, 0.8 meters wide and high, and located at the University of Florence. The gravel beach, berm, and breakwater models were constructed based upon in situ beach surveys. The laboratory quartz boulder beach and breakwater D50 approximated 3.0 mm and 3.6 cm, respectively. The laboratory hydrodynamics aimed to simulate a portion of storm measured at a local wave buoy during an event in October 2003 that lasted 54 hours. Ten wave runs were conducted with durations ranging from 9.5 - 43 min with programmed peak wave periods of 1.4 - 2.1 s and significant wave heights of 9.6 - 17.5 cm. Seven wave gauges were distributed along the wave flume, two adjacent to wave maker, three just offshore the breakwater, and two just onshore of the breakwater. The clear glass side of the flume was delineated to capture millimeter scale changes of beach and berm morphology. Wave transmission (Kt) values calculated using field-based measurements ranged from 0.33–0.52, suggesting that between 11–27% of the offshore energy is transmitted through the breakwater. In the laboratory simulation of the storm, the modeled Kt values under-predicted measured Kt values by 1–16% and the berm migrated onshore to the upper shoreface and flattened the overall beach profile.
Khalil, S. M.; Finkl, C. W., and Raynie, R. C., 2013. Development of new rRestoration strategies for Louisiana barrier island systems, northern Gulf of Mexico, USA
The rapid degradation of Louisiana's barrier island (BI) systems adversely impacts the vitality of strategic economic and biological resources (including aquatic habitat). Louisiana's BI systems have undergone landward migration through BI rollover, area loss and island narrowing as a result of complex interactions among land subsidence, sea-level rise, wave processes, inadequate sediment supply, and intense human disturbance. Consequently, the structural continuity of the BI shorelines has weakened as the islands narrowed, fragmented and, in some cases, submerged. Several multipronged restoration strategies are currently underway to develop effective interdisciplinary restoration projects that mitigate degradation of the Mississippi River delta plain and compensate for coastal land loss. Restoration of the BI systems requires strategies that protect interior wetlands and bolster the first lines of storm defense in a post- Hurricane Katrina-Rita-Gustav-Ike-Isaac and post-Deep Water Horizon era. Coastline degradation would have continued were it not for a series of massive barrier island restoration projects. Such efforts commonly consist of beach nourishment on the Gulfside and marsh creation on the bayside of barrier islands. Regionalizing monitoring, maintenance, and data management efforts support the still evolving scientific and engineering aspects of rebuilding BIs.
McCall, R.T., Masselink, G., Poate, T.G., Bradbury, A.P., Russell, P.E. and M.A. Davidson, 2013. Predicting overwash on gravel barriers.
A process-based non-hydrostatic flow model, which includes the effect of infiltration and exfiltration, but no morphology, is applied to simulate overwash events on gravel barriers. After calibration, the model is shown to produce similar predictions for overwash as the empirical Barrier Inertia Model for parameter combinations within the validity range of the empirical model. When applied to 25 historical storm impacts, the process-based model shows improvement over the empirical model in predicting overwash. The model is applied to study the sensitivity of overwash to input parameters outside the validity range of the empirical Barrier Inertia model. This analysis shows that two parameters currently missing in the Barrier Inertia Model, the depth of the gravel beach toe and the gravel beach slope, greatly affect the threshold criteria for overwash.
White, J.L., 2013. Measuring clast transport signatures at a barrier terminus.
At a macrotidal prograding and transgressive, mixed sand and gravel barrier, continuous gravel transport logging provides insights into the relationships between the incident hydrodynamics and the morphodynamics. Two piezoelectric gravel transport sensors (GTS) were aligned in either the cross-shore or the alongshore directions over two low and two moderate energy equinox spring tide events. GTS measure gravel transport as an electronic pulse, where the frequency and amplitude measures clast transport rate and presumably number coincident with the passage of a wave, or per event. Clast transport occurs in bursts characterised by greater than average amplitude peaks, thought to coincide with wave phenomena. Further, these bursts do not appear to progress in a linear relationship with the wave parameters. For example, series of burst can be greater before, or after high tide, and are often polymodal, and low wave energy transport rates can be greater than moderate transport rates. The cross-shore configuration measured the clast transport over a gravel substrate at a high water ridge, and the adjacent landward high tide swash zone. As expected transport frequencies were greater over the high water ridge than at the adjacent swash zone. However, the clast transport per wave can be greater at the swash than at the high water ridge, suggesting the importance of the prolonged breaking wave inducing clast transport. The average number of clasts transporting per event can be greater at the high water ridge than at the swash. Also, sediment volume changes were greater on the high water ridge, marked by small depositions, where as the swash zone could be depositional, or erosional. The longshore configuration measured the simultaneous clast transport over gravel or sand substrates. The transport frequencies were greater over the gravel than the sand substrate. Greater volumes of sediment were transported to landward over the sand than the gravel substrates. The clasts transporting over the sand substrate per wave can be greater than clasts transporting over the gravel substrate, suggesting the importance of sand transport and accumulation as a process associated with prograding gravel barriers. However, the average number of clasts transporting per event over the gravel were generally greater than over the sand substrates, hence gravel substrate clasts can transport but with little net transport direction. The deployment of GTS enables indications of gravel transport characteristics continuously within an active barrier system environment.
Abreu, T., Silva, P.A., Sancho, F. and Michallet, H., 2013. Use of the velocity defect law to assess sand transport rates.
This work uses a simple method based on the defect law that is able to reproduce the horizontal velocities within the wave bottom boundary layer, using a limited number of parameters. The theory is checked against the measured velocity profiles gathered with a high resolution Acoustic Doppler Velocity Profiler. The velocities were collected during an experimental project performed at the Large Oscillating Water Tunnel of Deltares under flat-bed/sheet flow conditions, allowing the analysis of the effects of wave nonlinearities and of a net current on the sediment transport processes. The velocity estimates are used to infer the time-varying bed shear stress, using the momentum-integral method. Secondly, the bed shear stresses are incorporated in a quasi-steady bed load formulation and the transport rate predictions are compared with the net transport rate measurements obtained in the same facility. The results show that the methodology presented in this work provides a suitable estimation of the horizontal near-bed sediment transport rates under non-linear oscillatory flows.
Bae, J.S., Kim, H.J., Choi, J., 2013. Surface Roller Effect Affecting on Shear Fluctuations of a SandyDuck Experiment under a Random Wave Environment.
Surface roller effect affecting on shear fluctuations of a SandyDuck experiment was investigated under a random wave environment by using the combination of SHORECIRC and SWAN. The surface roller, which is a strong turbulent region of waves that break and tumble shoreward, has been known to be significant for modelling of nearshore wave-induced motions. The surface roller forces to move the maximum of the cross-shore profile of the mean longshore current toward the shore, and it increases longshore current velocity in the sandbar trough region. Consequently its effect improves the predictions of mean nearshore circulations and surface elevation. The surface roller effect, which gives the corrections to surfzone dynamics, plays a significant role on the shear fluctuations of longshore current. In this study, shear fluctuation changes depending on the surface roller effect were numerically analyzed. As a result, since the surface roller effect moves the maximum of the cross-shore profile of the mean longshore current toward the shore, the location of shear fluctuations was moved toward the shore. And the surface roller effect suppressed rapid rip currents or separation of vortices due to shear fluctuation out of the surfzone, and decreased its fluctuation energy.
Calantoni, J., Landry, B.J. and Penko, A.M., 2013. Laboratory observations of sand ripple evolution using bimodal grain size distributions under asymmetric oscillatory flows
The heterogeneity of sand beds has been suggested to significantly impact the resulting sand ripple morphodynamics. However, the majority of previous experiments for sand ripple morphodynamics were conducted using only unimodal grain size distributions. Here we performed a series of ripple growth and transition experiments in a small oscillatory flow tunnel in the Sediment Dynamics Laboratory at the U.S. Naval Research Laboratory. Sand beds were constructed from mixtures of two unimodal sands median grain sizes of 0.30 mm (blue) and 0.70 mm (white), respectively. Experiments were performed with compositions of bimodal mixtures with percent by mass of 10/90, 25/75, 50/50, 75/25, 90/10. Additionally, similar experiments were performed for each of the unimodal cases (i.e., 100/0, 0/100). For each experiment, starting from a planar bed, three different flow forcing conditions were applied in sequential blocks (with minimum of one-hour duration) until the ripples appeared to be uniform and in equilibrium. We analyzed ripple characteristics such as migration rate, wavelength, height, and steepness as a function of the mobility number. Over a range of nearly identical mobility numbers, we observed opposing trends with migration rates increasing in one block forcing and decreasing in another, where the two blocks were comprised of different combinations of the semiexcursion amplitude and oscillatory frequency. The results suggested that the commonly used mobility number might not be appropriate to characterize ripple migration rates, especially for sediment beds composed of bimodal size mixtures. Overall, wavelength, height, and steepness are consistent with empirical ripple predictors. However, observed subtleties existed among the different forcing blocks across the same range of grain size distributions.
Ciavola, P., Contestabile, P., Aristodemo, F., and Vicinanza, D., 2013. Beach sediment mixing under drained and undrained conditions.
The paper describes a set of experiments undertaken at the Grosser Wellen Kanal (GWK) in Hannover on sediment mixing on a beachface exposed to the action of a buried drainage system. Experiments were performed using a set of drains (up to three working simultaneously), located at variable distance from the shoreline. Wave energy during the tests ranged from medium (0.59 m < Hs < 0.61 m) to high (0.76 m < Hs < 0.83 m). Beach profiles were measured at the end of each test. Further validation came from measurements using a grid of rods that were monitored at the same time as the beach profiles were surveyed. While some beach stabilization was observed for low energy conditions, for medium and high energy conditions the benefit of having the drains operative was not so clear. The comparison between beach profiler and rods showed good agreement regarding relative vertical accretion and erosion events. In any case, it was evident that the sedimentary effect on the beachface was confined to a narrow area above the drains. The drained area showed slightly lower values of sediment mixing under drained conditions, but evidently this factor was not important enough to trigger a widespread beach stabilization. Values of sediment mixing averaged across the whole beachface ranged between 2–4 % and 4–6 % of the breaking wave height respectively for high and medium energy wave conditions. Grain size, beach slope and drain configurations used here are fully comparable to field installations present in the literature.
Colenutt, A., Mason, T., Cocuccio, A., Kinnear, R. and Parker, D., 2013. Nearshore high resolution substrate and marine habitat mapping to inform marine policy and coastal management.
The Defra-funded National Network of Regional Coastal Monitoring Programmes of England, through collaboration with the Maritime and Coastguard Agency's Civil Hydrography Programme, are increasingly utilising cost-effective technology to achieve 100% seafloor coverage to International Hydrographic Organization (IHO) Order 1a standard, of the nearshore zone from about Mean Low Water Springs to approximately 1km offshore. Detailed specifications have been developed to ensure efficient acquisition of swath bathymetric data that are accurate, repeatable, maximise interoperability and are made freely available. Analysis of seabed substrate and habitat maps, which identify zones of exposed bedrock and surficial deposits of coarse, fine and mixed sediments, provide spatial detail of seabed features, such as sand waves, rock outcrops, pinnacles and scour and provide baseline conditions for monitoring of marine ecosystems. Interpretation and production of marine geology maps may also provide important information about seafloor composition and structure, physical properties and sedimentological and geological processes such as natural hazards. The methodology developed for data processing and interpretation combined with examples from a suite of detailed indicative substrate and marine habitat maps is presented. Interpretation of the full coverage swath bathymetry and acoustic backscatter information and ground-truthing data enables high resolution marine-related spatial and temporal substrate whilst habitat maps provide a sound multi-disciplinary scientific evidence base to inform development of European and UK marine environmental policy and planning, and are valuable tools for managing the sustainable use and conservation of coastal and marine resources, thus aiding the integration of terrestrial and marine planning regimes.
De Winter, W., Wesselman, D., Grasso, F. and Ruessink, G., 2013. Large-scale laboratory observations of beach morphodynamics and turbulence beneath shoaling waves and plunging breakers.
In 2012, large-scale laboratory experiments were carried out in the Deltagoot in the framework of the Hydralab IV-funded BARDEXII project. The overall project aims were to examine the effect of swash/groundwater interactions to sand transport and morphological development in the swash zone and, additionally, to investigate the sediment exchange between the swash and surf zone. Work package 5 in the BARDEXII project focused on this second aim and, therefore, paid particular attention to the effect of surface-generated turbulence on sand suspension and on the direction and magnitude of the subsequent sand transport. We know from earlier, predominantly small-scale laboratory experiments that breaking-induced surface-generated eddies can penetrate through the water column to hit the sea bed and suspend sand. The inherently intermittent nature of this turbulence and hence suspension is strikingly at odd with sand transport equations that assume sand transport to be related to the orbital flow to some power. Although attempts to include breaking-induced turbulence into sand-transport equations have been performed to improve the modeling of swash-surf sand exchange, our quantitative understanding of the effects of breaking-induced turbulence on sand suspension is limited because of a lack of simultaneous and accurate measurements of turbulence and sand suspension under breaking waves. This paper will describe the experimental design for this work package and present preliminary results on (1) the bathymetric evolution during the series of tests and (2) the vertical turbulence structure beneath shoaling and breaking waves.
ERM, A., BUSCHMANN, F., LISTAK, M., REBANE, J., and TOMING, G., 2013. Underwater experiments and a theoretical model – case study in Tallinn Bay. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
The aim of this study was to experimentally validate a theoretical shear stress model for calculating critical shear velocities that cause sediment resuspension and bed load transport. Long period measurements with an acoustic Doppler velocimeter were carried out in the Tallinn Bay, in three stations with different bottom geology. Water turbidity was measured at the same level and a camera system was used to register sediment resuspension. Measurements showed that a detailed model must be used in case of strong interactions of waves and currents near the bottom. If currents are weak then a simple Nielsen model can be used to estimate sediment resuspension conditions. Thickness of the bottom boundary layer was found being 1 – 10 cm and the skin friction layer being 0.07 - 0.7 cm. A pilot study using constructed autonomous underwater particle image velocimetry device (PIV) showed that the upper part of bottom boundary layer i.e. the wave boundary layer could be observed by a field PIV-device.
Flöser, G., Nauw, J., Burchard, H., Riethmüller, R., 2013. Observational evidence for the inward transport of suspended matter by estuarine circulation in the Wadden Sea.
Observational evidence is presented that corroborates the hypothesis that estuarine circulation represents a generic process in the Wadden Sea, independent of (the amount of) river runoff. Long-term current velocity data from three locations in the Wadden Sea, taken on moored acoustical current meters, onboard anchored ships and across-channel ship-of-opportunity platforms show in all cases features concurring with the predictions of the theory: a tidally residual outflow of Wadden Sea waters in the upper part and a residual inflow of seawater in the lower part of the water column. This may be regarded as a further confirmation for a generic process to import suspended sediments from the German Bight / North Sea into the Wadden Sea against the prevailing concentration gradient.
Grifoll, M., Gracia, V., Fernandez, J. and Espino, M. 2013. Suspended sediment observations in the Barcelona inner-shelf during storms.
This contribution describes in detail the Suspended Sediment Concentration (SSC) obtained from an observational set at 24 m depth in the Catalan inner-shelf (North-western Mediterranean Sea) analysing the dominant processes affecting sediment dynamics during storm events. A clear correlation between SSC, energetic waves, and along-shelf currents events has been found. Peaks in river discharge associated to rainy events are also correlated with SSC measurements. Measured conditions highlight the different sediment dynamic situations present during short-term events such as “wet” and “dry” storms with similar wave height. SSC observed during “dry” conditions are correlated with wave action. On the other hand, SSC peaks during “wet” conditions are primarily caused by wave action, along-shelf current, and river discharge. Observed sediment fluxes during storms are larger in spring than during fall. Although the observations present similar characteristics to other inner-shelf regions in the NW Mediterranean Sea, the results reveal a non-negligible influence of the along-shelf current in sediment dynamics. The results presented here contribute to advance in the understanding of sediment dynamics in wave-dominated regions such as the Catalan shelf.
Malvárez, G., Jackson, D.W.T., Navas, F., Alonso, I., Hernandez-Calvento, L. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1539–1544, ISSN 0749-0208.-->
The Corralejo dune system in Fuerteventura in the Canary Islands (Spain) is an aeolian landscape whose genesis and evolution has commonly been associated with a traditional input-output model by which sediments entered from northern beaches and accumulation occurred in the southernmost (land-locked) sections of the dune field. Satellite images as well as aerial photographic evidence over the last 60 years, however, shows that the evolution of the dunes may reflect a more complex scenario in which under current settings and orientation of the coast, a sediment leakage back into the southern coastal environment is occurring. Under these circumstances, longshore currents can then transport this sediment back along the coast toward its initial landfall location, thus re-joining a sediment-recycling pathway. Human occupation of such a system can sometimes interrupt this pathway, seriously impinging its functionality. Better understanding of its morphodynamics at this scale will help negate these impacts.
In this paper, we present a conceptual model for the functioning of the beach and dune systems of Corralejo, purporting that southbound winds and wave fields induce large-scale refraction patterns that in turn generate an intense increase in wave-induced radiation stress at the south tip of the dune field. The work highlights the need to further our knowledge of dune field dynamics in arid coastal settings, integrating aeolian and wave processes in order to promote appropriate science-led decision making for both environmental management and spatial planning.
Masselink, G, Turner, I.L., Conley, D.C., Ruessink, B.G., Matias, A., Thompson, C., Castelle, B. and Wolters, G., 2013. BARDEX II: Bringing the beach to the laboratory – again!
Proto-type laboratory experiments are particularly useful in coastal research when forcing parameters are modified in a way that is impossible to achieve in the field, and where installation and maintenance of instrumentation requires absence of waves. In 2008, the Barrier Dynamics Experiment (BARDEX) took place in the Delta Flume, the Netherlands. This project, funded by Hydralab III, focused on the effect of varying wave, sea level and beach groundwater conditions on a gravel beach (D50 = 10 mm). In 2012, a similar project was carried out, referred to as BARDEX II, this time funded by Hydralab IV and on a sandy beach (D50 = 0.42 mm). During the experiment, a 4.5-m high and 70-m wide sandy barrier was constructed in the flume with a lagoon situated to the landward. The barrier was instrumented with a very large number (> 200) of instruments and subjected to a range of wave conditions (Hs = 0.8 m; Tp = 4–12 s) and varying sea and lagoon water levels. Five distinct test series were executed over a 20-day period: series A focused on beach response due to accretionary/erosive wave conditions and a high/low lagoon water level; series B investigated the effect of a lower sea level on nearshore bar dynamics; series C simulated tidal effects; series D addressed the swash/overtopping/overwash threshold; and during series E the beach-barrier system was subjected to an extended period of energetic overwash conditions. This paper will describe the experimental design and the test programme during BARDEX II.
Mentaschi L., Besio G., Cassola G. and Mazzino A., 2013. Developing and validating a forecast/hindcast system for the Mediterranean Sea
In this work a study of the performances of the WAVEWATCH III (WWIII) model in the Mediterranean basin is presented. Analysis is carried out referring to seventeen case studies corresponding to heavy storms in northern Tyrrhenian basin (Ligurian sea) in the last twenty five years. Simulation results are validated using buoy data provided by the Rete Ondametrica Nazionale (RON). An analysis of the usage and performances of different statistical error indicators is provided, showing that widespread NRMSE indicator is biased towards models that underestimate prediction. The well established source terms parameterization by Tolman and Chalikov (1996) has been compared with the one proposed by Ardhuin et al. 2010, set up with the parameterization by Bidlot et al., 2005, and with the set known as ACC350. The obtained results reveal that the ACC350 parameterization works better in severe conditions, though tends to overestimate wave height and underestimate period. A further sensitivity analysis in the parameters space is carried out around ACC350 parameterization, finding that variations in the default set of parameters, involving small wave growth reduction or an increase of energy dissipation, lead to a slight improvement of the overall simulation performances.
Olivier.G., Senechal.N., In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1557–1562, ISSN 0749-0208.-->
Swash hydrodynamics were investigated on an intermediate beach under calm, constant offshore conditions using runup data from video measurements at the scale of a single high tidal cycle. Two different local profile changes occurred on the upper face of the beach between two consecutive days (20cm of erosion and 21cm of accretion). Two cross-shore transects have been chosen for each of the two maximum profile changes (two Accretive Transects and two Erosive Transects). The swash zone was associated with moderately reflective conditions (Iribarren parameters up to 0.9 and a beach slope of 0.058–0.072). Results show a strong disparity in the mean runup heights between transects of the two areas; mean runup elevation for Accretive Transects being twice higher than for Eroding Transects while energy partitioning between incident and infragravity energy was very similar and consistent with moderately reflective conditions. At the scale of the single swash event, results show that uprush typically exceeded backwash duration by ~ 0.8s for Accretive transects. Nevertheless, the general observed trend is a quasi-symmetrical uprush and backwash durations and velocities, consistent with previous observations. Regarding the upper beach slopes, the Accretive part became slightly flatter while the Erosive one became steeper but both tending towards the same beach slope, suggesting that the upper beach seems to adjust towards an equilibrium profile through a balancing of the upper beach face.
Oyedotun, T.D.T., Burningham, H. and French, J. R., 2013. Sediment sorting and mixing in the Camel Estuary, UK
The Camel estuary, north Cornwall, UK, is characterised by extensive intertidal flats and saltmarsh that grade into beach and sand dunes at the mouth. This and other Cornish estuaries have received considerable attention in terms of the impact of mining (principally for Sb and Sn) on sedimentation. Significant changes in sediment supplied to these systems from the local catchment occurred as a result of mining activity. The primary impacts were on supply, sedimentology and mineralogy, and the peak of these impacts occurred in the 19th century. Although pollution and chemistry indicators have been considered extensively in past studies, very little consideration has been given to the nature of estuary-coast linkages in terms of sedimentary processes. This study focuses on the sedimentological characteristics of surface and shallow intertidal sediments within the Camel estuary system. Short (15cm) sediment cores obtained from 44 sample sites were sliced at 1cm intervals and grain size analysis (using a Malvern Mastersizer 2000) was undertaken on these subsamples. A wide range of grain size parameters is examined to explore the evidence for sediment mixing and extensive sediment transport processes within the estuarine system. Results show that the sediments are dominated by medium to fine sands throughout except in the inner estuary. Sediment is moderately well sorted in the outer and mid-estuary and poorly sorted in the inner estuary. It is possible that valley shape influences sediment transport processes and inhibits the supply and active reworking of marine sands in the inner estuary.
Pedrozo-Acuña, A., Resendiz, D., Gutiérrez, C., 2013. Experimental study on sediment advection and beach response under plunging wave breaking.
This paper presents an experimental investigation into the morphological response of beaches under the action of plunging wave breaking. Experimental results performed under the same wave conditions, allowed the association of beach evolution to its porosity. Firstly a beach profile which presented the generation of a clear berm at the top of the profile and a beach step below the SWL (higher porosity) was illustrated. Secondly, an erosive condition of beach profile was characterised (lower porosity). The morphological responses of both beaches were differentiated in terms of the porosity of the beach, which highlight its role in the resulting spatio-temporal nature of the momentum balance under plunging wave breaking. Additionally, BIV derived velocities were utilised as a tool for the investigation of hydraulic regimes responsible of generating different beach responses and sediment sorting in the laboratory. Through Euler's equation the total acceleration was deconstructed, allowing a careful assessment of the contribution of each the acceleration terms to the resulting momentum balance. Notably, the contribution of the local acceleration term is insignificant all along the beach profile, while the role of advective terms cannot be overlooked.
Petruzzelli, V., Gracia Garcia, V., Gironella i Cobos, F.X. and Petrillo, A.F., 2013. On the use of lightweight materials in small-scale mobile bed physical models.
In this paper an evaluation of the morphodynamic response of different relatively common lightweight materials in small-scale physical models is presented. Results must serve to provide an overview of the various aspects likely to sensibly influence on sediments morphological response in small-scale tests and to determine the possible suitability of the low-density particles investigated for coastal modelling. Different granular materials, covering densities between 1150 kg/m3 and 2650 kg/m3 and median diameters from 0.07 mm to 1.5 mm have been selected to reproduce the experiments carried out in 1987 in the Groβen Wellen Kanal (Hannover, Germany). Tests have been performed at the Technical University of Bari (Bari, Italy) at scale 1:100 and at the Technical University of Catalonia (Barcelona, Spain) at scales ranging from 1:15 to 1:50, using irregular wave conditions and geometries based on Froude scaling. An analysis of the erosion and deposition volumes, the shoreline evolution and the beach profile slope has been done. Results show different mobility rates and beach profile morphodynamics depending on particles intrinsic characteristics, demonstrating that for lightweight materials not only settling velocity is paramount to determine particles suitability and morphodynamic response. Finally, a comparison between the morphological evolutions of the models and the prototype moving along the beach profile cross-section is presented.
Rollnic, M. & Rosário, R.P., 2013. Tide propagation in tidal courses of the Pará river estuary, Amazon Coast, Brazil. Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1581–1586, ISSN 0749-0208.-->
On the Pará River (estuary) there are approximately one hundred tidal channels. These channels are important systems in both ecological and socio-economic systems. This paper aims to determine the tidal propagation pattern in the tidal channels in the dry and rainy seasons. Three tidal channels were selected on the left margin ( Marajó Island). In a first experiment, two pressure sensors were installed in each channel for 13 hours during a spring tide, one in the mouth and the other approximately 3 km upstream. In a second experiment, 3 pressure sensors were installed in one of the channels (36 days): one outside the channel (Pará river), one in the mouth and another one upstream in the channel. The first experiment revealed that the channels have similar pattern and asymmetric tidal regime, whose flood takes approximately 4 h and the ebb, 8 hours. The absence of an effective river discharge may favour the flood. The presence of sandy banks in the mouth of these channels trap the water inside, which makes the ebb last longer. In the second experiment, harmonic tidal constituents were obtained at the outside point. In the channel and channel mouth there was no variation in the low tidal level during the dry season, possibly due to morphology effects. In the rainy season there was slight variation in low tide level and this was more evident on the spring tide.
Sclavo, M., Benetazzo, A., Carniel, S., Bergamasco, A., Falcieri, F.M., and Bonaldo, D., 2013. Wave-current interaction effect on sediment dispersal in a shallow semi-enclosed basin
The shallow northern Adriatic Sea (namely Gulf of Venice) serves as a model for exploring the interaction of surface gravity waves and oceanic currents and how they influence bottom sediment dispersal and bathymetry evolution. This wave-current interaction effect is investigated using the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. COAWST relies on the Regional Ocean Modeling System (ROMS), the Simulating WAves Nearshore (SWAN) model, and the CSTMS (Community Sediment Transport Modeling System) models and routines. The 2-way data transfer between wave and ocean circulation models is synchronous via MCT (Model Coupling Toolkit), with ROMS providing to SWAN the 2-D current field, free surface elevation, and bathymetry. COAWST modeling system is implemented on two computational grids at different horizontal resolution: a parent grid (with resolution of 2.0 km) covering the whole Adriatic Sea and a child grid resolving the Gulf of Venice at a resolution of 0.5 km. Simulated waves and currents are validated against in-situ observations at the CNR-ISMAR Acqua Alta oceanographic tower, located 15 km off the Venice lagoon. The analysis of wave-current interaction effect on sediment dispersal and sea bottom evolution are performed over the 2011 winter season (January-March) with particular focus on the waves generated by dominant and prevailing winds blowing on the Adriatic Sea: Bora and Sirocco. Results show that while the effects on bottom stress may vary depending on wave propagation and current direction, the effects on advective dynamics may become dominant particularly in presence of severe storms with parallel wave propagation and global circulation, which is the case of Bora storms in northern Adriatic Sea.
Thompson, C.E.L., Kassem, H. and Williams, J., 2013. BARDEX II: Nearshore sediment resuspension and bed morphology.
Sediment resuspension in the region outside the surf zone is known to contribute to the morphological response of barrier beaches to wave forcing, such as onshore bar migration processes. However, few measurements in this region exist, limiting our ability to quantify its contribution. These processes are complicated by the presence of bedforms in the nearshore, which alter the sand transport processes while modifying bed roughness in a complex feedback mechanism. The Hydralab IV funded BARDEX II experiments, which took place in the Delta Flume in 2012, were used to provide measurements of these processes in the nearshore of a sandy barrier beach (D50 = 0.42mm) under a range of wave conditions (Hs = 0.3 - 0.8 m; Tp = 4 – 12 s) and water levels, through deployment of a suite of acoustic instruments measuring flow velocity, near-bed turbulence, sediment resuspension profiles and bed morphology in cross-section and plan view. Initial findings indicate that sediment suspension in the nearshore appears to be controlled by a combination of near-bed turbulent bursting processes which results in near-instantaneous low concentration suspensions restricted to the bottom boundary layer, and vortex shedding from bedforms which results in higher concentration suspensions which are larger in scale than vertical eddy sizes, and perpetuate outside of the bottom boundary layer.
Umeda, S., 2013. Scour process around monopiles during various phases of sea storms
An understanding of scour processes during the passage of sea storms is particularly important for the design of structures and the development of effective scour protection works. This study investigates the scour process at a slender monopile during various phases of a storm to give a better understanding of scour and backfilling mechanisms. Laboratory experiments were carried out to simulate the scouring effect at a pile by a storm consisting of a succession of seven phases of irregular waves. Detailed examinations were conducted to explore variations in the scour depth and bed topography. It turns out that scour patterns resulting from irregular waves can be characterized using the Keulegan-Carpenter number and the Shields parameter (KC1/3, θ1/3), which require significant near-bottom velocities. The scour process during a heavy storm consists of four main phases: (1) no bed deformation, (2) accretion, (3) erosion, and (4) backfilling. The amount of scouring increases as the order of the phase increased during a storm. The scour during phase (2), accretion, is in the transient condition between clear-water scour and live-bed scour. The scour in phase (3), erosion, is distinguished by live-bed scour, horseshoe vortices, vortex shedding and cone-shaped scour holes with vortex ripples. The influence of backfilling, phase (4), as a storm decreases in intensity, has a significant effect on the scour depth around the perimeter of the pile. The scour depth at the end of the event is much lower than the maximum scour depth during the event. However, backfilling of the scour hole makes only a weak recovery in total sediment volume around the pile, because the backfilling is confined almost exclusively to the neighborhood of the pile.
Vaz, L., Plecha, S., Dias, J.M., 2013. Coastal wave regime influence on Ria de Aveiro inlet dynamics. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1605–1610, ISSN 0749-0208.-->
The adjacent coastal zone of Ria de Aveiro lagoon is exposed to a highly energetic wave climate, with a yearly mean significant wave height of 2–2.5 m and wave periods of 9–11 s, corresponding to WNW to NNW swell. Consequently, it should be expected that the lagoon inlet hydrodynamic be dependent on the coupled forcing of tidal wave and wave regime. Thus, the main goal of this study is to assess the influence of the coastal wave regime at the inlet channel dynamics. The modeling system MORSYS2D, comprising the hydrodynamic model ELCIRC coupled with the wave model SWAN, is used to perform this study. The methodology developed consists in forcing the numerical models with local tidal harmonic constituents and with different constant regular wave scenarios typical of the northern Portuguese coast (high and normal wave activity and absence of waves). Under the normal wave activity scenario results show that the inlet channel hydrodynamics is mainly dominated by the tidal forcing. For the highest wave regime are found higher sea levels induced by the wave set-up. Consequently, it was found that the storm events induce important wave's set-up that change the inlet hydrodynamics, requiring that the coupling between waves and tides should required to accurately represent the physical processes of the lagoon. Although the dominant forcing of the Ria de Aveiro inlet hydrodynamics is the tide, it may be concluded that fluctuations at the wave regime influences the sea level and current velocity at the Ria de Aveiro inlet.
Vonhögen-Peeters, L.M., Van Heteren, S., Wiersma, A.P., De Kleine, M.P.E. and Marges, V.C., 2013. Quantifying sediment dynamics in the Dutch Wadden Sea using bathymetric monitoring series.
During the last millennium, human intervention has had an increasing impact on the bathymetry of the Wadden Sea. The significance of these human-induced changes for the decadal-scale development of the Wadden Sea in light of natural sediment dynamics is still unknown. We compared a series of 20th-century bathymetric grids and the top of the Pleistocene to calculate the decadal- to millennium-scale net sediment dynamics within the study area. Mean annual net sediment dynamics as determined from these comparisons is dependent on the time period considered. It is as high as 53 million m3 for 1999–2006, the shortest period considered, but less than 3 million m3 for the entire Holocene. The annual increase in accommodation space within the present confines of the Wadden Sea, resulting from relative sea-level rise, local subsidence related to gas extraction, sand and shell mining, and increases in tidal amplitude, is less than 10 million m3. A comparison of this relatively small volume with calculated short-term annual net sediment dynamics shows that processes transporting sediment in the Dutch part of the Wadden Sea are easily capable to fill new accommodation space. The main factors governing long-term system resilience are the availability of sediment in source areas outside the tidal basin and the capacity of inlets to import this sediment at sufficient rates. Large-scale nourishment is carried out to prevent the Wadden Sea from cannibalizing adjacent island heads and ebb-tidal deltas. The present study may help in fine-tuning this regional nourishment strategy.
Yamada, F., Tateyama, R., Tsujimoto, G., Suenaga, S., Long, B. and Pilot, C. 2013. Dynamic monitoring of physical models beach morphology and sediment transport using X-ray CT scanning technique
A medical X-ray CT scanner was applied to dynamic measurements of beach profile changes, sedimentary structures, and sediment transport processes during wave actions in the laboratory experiments. An acrylic flume 7 m long and with an inner rectangular cross-section of 0.3 m × 0.3 m passes through the mobile gantry of a medical X-ray CT-scanner. The experiments were conducted at the Institut National de la Recherche Scientifique (INRS) at the University of Quebec from August 18 to October 16, 2011. The flume was filled with Ottawa sand (d50 = 0.147 mm) with uniform slope of 1/15. The water depth over a horizontal bed is 0.2 m. Regular waves were used with wave height of 4.0 cm and wave period of 0.7 s. In order to measure the cross-shore evolutions both of beach profiles and sediment transport process, the CT-scanner moves automatically along the flume. Therefore, the core samplings were not needed and the continuous measurements of beach profiles and sediment transport process in cross-shore directions can be conducted with non-destructive and non-contact conditions. By reconstructing three-dimensional images using Hounsfield units, the evolution of beach morphology was examined. Because medical X-ray computed tomography has the advantage of a data acquisition time of 1.0 seconds for sediment transport processes during wave action, the obtained data, such as that of the suspended and bed load, are useful for clarifying the mechanism of profile change and validating numerical models.
Azzellino A., Kofoed J.P., Lanfredi C., Margheritini L., Pedersen M., 2013. A Marine Spatial Planning framework for the optimal siting of Marine Renewable Energy Installations: two Danish case studies.
In this analysis two Danish case studies are investigated using a spatial planning approach. The first case study concerns the area on the west coast of Denmark that has been elected as test site by the Danish Wave Energy Center (DanWEC), a foundation constituted by local authorities, Aalborg University supported by the national wave energy industry. The second case study attains the Danish portion of the western Baltic sea, where many offshore windfarms are already installed and many projects are in construction or in the planning stage. The environmental background for the two areas is considered through set of multiple indicators (e.g. sea bottom topography and characteristics, marine biodiversity, presence of vulnerable species). Environmental indicators are aggregated into environmental impact indexes that constitute the basis for evaluating the site suitability for Marine Renewable Energy Installations (MREIs). Concurrenlty, areas of potential conflicts between the interests of MREI developers and commercial, recreational users are identified. Multivariate analysis techniques allow to disentangle the different components of the environmental vulnerability of the two areas and suggest sound criteria for the optimal siting of these infrastructures. The two case studies, concerning respectively a regional and local scale, offer good examples about how spatial planning has the potential to guide the transition from the single sector management toward the integrated management of sea uses.
Lawless, M.R and Rodger, D.W., 2013. Development of the European Tidal Database and its Potential Application to Marine Renewables
Tidal flows, sea levels and currents influence coastal flood and erosion risk, flood defence design, coastal management and renewable energy production. Historically data for these variables have been obtained from tide gauge records. However, this information is limited in both time and space. Consequently, analysis and planning for sites between gauges has traditionally been established through simple interpolation techniques, thereby leading to higher levels of uncertainty than desirable. For a more reliable application to coastal and ocean engineering, a more holistic approach is required.
Initially developed as a response to the increasing threat of flooding from the sea, JBA developed a comprehensive suite of high-resolution hindcast tide-surge models for Western Europe, collectively called the European Tidal Database. The models within this suite simulate every tide that has occurred around the coast of the UK, Ireland and Western Europe for the 45 years between 1957 and 2002. In addition to the tidal forcing, the models are also forced at the surface by windstress and atmospheric pressure data interpolated from the European Centre for Medium Range Weather Forecasts (ERA-40), simulating surge affects. The output from the models can be visualised as a high resolution ‘virtual tide gauge record', including a 45-year record of tide, current and surge levels for more than 20,000 closely spaced points along our coasts, estuaries and tidal rivers. This model data provides unprecedented long-term historical information that can be used to evaluate exposure to coastal flood risk at any location more accurately than previous approaches.
Currently the models within the UK Tidal Database are being used to determine surge relationships between real-time gauges for the purposes for flood warning and extremes analysis, although its application is planned to span a range of additional coastal engineering disciplines. In particular, the results of the model could be used to determine the potential power of harnessing tidal flows at any location by determining the energy returns that would have been achieved had devices been in the sea over the last 45 years. This paper described the modeling that underpins the European Tidal Database and discusses its broader applications.
Matutano, C., Negro, V., López-Gutiérrez, J.S., Esteban, M.D. and del Campo, J.M, 2013. Dimensionless wave height parameter for preliminary design of scour protection in offshore wind farms
The scour phenomenon jeopardizes the operating capacity of offshore structures since it compromises their stability. The study of this phenomenon in the field of offshore wind farms began few years ago. Considering that these structures are subjected to waves, currents and tides.
This article describes the results of an investigation aimed at the analysis methods used in the design of the protections against scour phenomenon on offshore wind farms in transitional waters, using medium and large diameter monopile type deep foundations.
In order to do this, a thorough review of those premises was performed, from one of the first experiences in 1991 (Denmark), to the recently implemented and proposed in the UK, defining its main characteristics (acting maritime climate, the correlation between wave height and period associated with a given recurrence) and the type of protection used (weight average, nominal diameter in the case of breakwater type protection, width and behavior).
Taking into consideration the experience with offshore wind farms in current operation, the design data analysis, the basis of climate and the soil-structure interaction, the dimensionless wave height parameter (H0), the erosion extension (Lext), and the quantification of maximum scour depth (Smax) have been calibrated for a preliminary design of protections around a large diameter pile, obtaining initial values for H0 in the vicinity of 6 and 15, and values for the extension of protection design between L/4 and L/2.
Posner, A.J., O' Sullivan, K., Murphy, J., 2013. Economic and Environmental Impact Appraisal of Commercial Scale Offshore Renewable Energy Installations on the west coast of Ireland
This study investigates the feasibility of installing a 250MW commercial scale marine energy park (wind and wave energy), both in terms of economics and environmental impacts, off the Belmullet coastline in Co. Mayo, Ireland. This site corresponds to the Atlantic Marine Energy Test Site (AMETS) where an environmental impact assessment has been carried out previously. A probabilistic economic model for the evaluation of wind and wave hybrid designs has been developed and is used in this study. This life cycle cost analysis (LCCA) uses discount rates suggested by industry and investigates the variation in the levelised cost of energy (LCoE) for various farm arrangements. A study using numerical wave modelling software has been undertaken to determine the modification to the wave field and thus the subsequent effects on sediment transport processes and shoreline evolution on the Mayo coast with the aim of optimising the arrangement of the marine energy park with respect to LCoE and environmental impacts. This methodology is a significant advancement in studies of the optimisation of wave farm arrangements. The methodology firstly consists of a capital expenditure model for pricing the farm infrastructure, secondly, a hydrodynamic analysis of the offshore wave conditions incident on the farm of devices is performed and the wave height incident on each device is passed as an input to the energy yield model, which is coupled with an operations and maintenance model. A financial calculator, which employs discounted cash-flow techniques, is employed to calculate the LCoE. This study demonstrates that there is an optimum arrangement for a renewable energy farm of wave energy converters (WEC), and that the addition of wind turbines can significantly alter this optimum arrangement.
Ransley, E., Hann, M., Greaves, D., Raby, A. and Simmonds, D., 2013. Numerical and physical modelling of extreme waves at Wave Hub
With a history of international failures, the survivability of coupled systems of wave energy devices and their moorings, particularly those to be installed at development sites like Wave Hub, is surrounded by uncertainty. Potential design solutions require a better understanding of the hydrodynamics and structural loading experienced during extreme events, like rogue wave impact, in order to mitigate the risk of device and mooring failure. Rogue waves are waves with amplitudes far greater than those expected, given the surrounding sea conditions. Intense study into these events stems from their potential for catastrophic impact on ocean engineering structures. However, little is known about their physical origins and, currently, there is no consensus on their definition or explanation of the mechanism which drives them. This paper concerns the numerical modeling and experimental validation of extreme rogue wave examples at the Wave Hub site. Using hindcast data, the 100 year extreme wave at the Wave Hub site is determined. This extreme wave is replicated in Plymouth University's new COAST Lab using a NewWave, dispersive focusing input. To simulate and analyse these events, we duplicate these conditions in a numerical wave tank (NWT), solving the fully nonlinear Navier-Stokes equations, with a free surface, using the Volume of Fluid (VoF) method and open source CFD library OpenFOAM®. The comparison shows that the CFD software is capable of simulating focused waves similar to those produced in the physical tank but tends to overestimate the crest heights. It is also noted that nonlinear effects are important when considering the shape and location of focused wave events.
Agustín Sánchez-Arcilla, Daniel González-Marco, Joaquim Sospedra, Ana Palomares, Joan Pau Sierra, Frieder Schuon, Manuel Espino, Manel Grifoll, Elena Pallarés, Pedro Angel Jiménez, Jorge Navarro
Sánchez-Arcilla, A., González-Marco, D., Sospedra, J., Palomares, A., Sierra, J.P., Schuon, F., Espino. M., Grifoll, M., Pallarés, E., Jiménez, P.A. and Navarro, J. 2013. Meteo-oceanographic simulations and observations to assess the potential of offshore wind farm in a NW Mediterranean shelf.
Renewable marine energy is important in squeezed Mediterranean coastal zones. Wind turbines deployed over the narrow Catalan continental shelf require accurate wind/wave/current fields for a reliable design, operation and maintenance. This paper presents the large (comparative to other open sea areas) errors in meteo-oceanographic predictions for semi enclosed domains such as the coastal sea off the Ebro Delta coast. The emphasis is on the sequence of high resolution coupled and nested models and the role of in situ collocated measurements for calibration and validation.
Shin, B-S, Kim, K-H, 2013. Effective tidal power generation with reduced environmental impact
Regarding ocean energies, tidal power generation has a great advantage on large development possibilities despite of its huge construction cost and difficulty in finding an applicable location. Once tidal power generation is developed, various developmental benefits are expected such as semi-permanent energy production, a bridge role, tourism resource effects, an adjustability of flood inundation at inner bay and other multi-development effects. Nevertheless, unfavorable impacts on bay environments have also been pointed out. The environmental problems include mud flat extinction and marine eco-system disruption. The participation of local residents is essential to resolve ecological and socioeconomic issues. In this study, the feasibility of tidal power generation is examined by reviewing the hydraulic characteristics of a target area on the west coast of Korea. The tidal flat at the site serves as a habitat and feeding ground for numerous aquatic species that the local residents benefit in their fishing industry, and also acts as a replenishment of water-table levels and a natural filter of pollutants. The purpose of this study is to predict negative effects of tidal power generation in ocean ecosystem. In addition, a desirable tidal power generation arrangement is proposed by investigating ecological and sociological effects on the environment. Field observations were carried out to understand hydraulic characteristics of the target area and to select the location of a water gate and a hydraulic turbine for tidal power generation development with its anticipated influence on the environment. Particularly, high quality data have been obtained by Ocean TMS(Telemetric Monitoring System) which is planned for continuous acquisition of real-time data. Environmental change prediction has become an increasingly important topic for public debate. Precise data is required for accurate predictions on artificial environmental changes.
Shin, S., Lee, K.-H., Kim, D.-S., Kim, K.-H., and Hong, K., 2013. A study on the optimal shape of wave energy conversion system using an oscillating water column
With the intention of diversifying energy sources, the use of natural and renewable energy sources such as sunlight, wind, tides, geothermal heats and waves is attracting favorable attention. Furthermore, current environmental issues, including global warming, ozone depletion and nuclear problems, promote development of renewable energy technologies. Many renewable energy technologies are however still under progress. Among these, the wave energy conversion system using an oscillating water column (OWC) is nearing commercial stage. OWC use the air flow induced by the vertical motion of water column in the air chamber as a driving force of turbine. Although it is well known that OWC is one of the most efficient devices to harness wave power, there is still much uncertainty about the relationship between the optimal shape and its hydrodynamic performance under the confined wave conditions. In this study, we propose a new computational fluid dynamics solver using on the immiscible two-phase (gas and water) flow model to simulate an OWC system in a two and three dimensional numerical wave tank. The numerical experiments focus on air flow velocity directly related to the working of turbine to survey the optimal shape. In order to validate the developed numerical model, laboratory experiments for the simplified OWC are carried out in a wave tank under regular wave conditions. The comparisons between the results of the developed numerical model and experimental data reveal a favorable agreement between the air flow velocity as well as the water surface profiles. Based on the validated numerical model, the effects of the inlet and chamber shapes including length, height, width and slope on the maximum air flow velocity are numerically investigated. As a result, in case the non-dimensional chamber width normalized by the incident wave length is in the range of 0.12 to 0.43, the maximum air flow velocity occurs with the increase of the inlet height and shortness of the inlet length.
Vicinanza, D., Nørgaard, J.H., Contestabile, P. and Andersen, T.L., 2013. Wave loadings acting on Overtopping BReakwater for Energy Conversion.
Any kind of Wave Energy Converter (WEC) requires information on reliability of technology and on time required for the return of the investment (reasonable payback). The structural response is one of the most important parameters to take in to account for a consistent assessment on innovative devices. This paper presents results on wave loading acting on an hybrid WEC named Overtopping BReakwater for Energy Conversion (OBREC). The new design is based on the concept of an integration between a traditional rubble mound breakwater and a front reservoir designed to store the wave overtopping from the incoming wave to produce electricity. 2D hydraulic model tests were carried out at the Department of Civil Engineering, Aalborg University (Denmark). The analyses of hydraulic model tests have identified the main shapes assumed by wave surfaces at the breakwater and respective spatial and temporal pressure distributions. Load measurements were compared with the most used prediction method for traditional breakwaters, available in the Coastal Engineering Manual (U.S. Army Corps of Engineers, 2002). These results suggest to use the experimental data as design loadings since the design criteria for the innovative OBREC are under development.
Cooper, J.A.G., Smith A.M., and Arnscheidt, J. 2013. Contemporary stromatolite formation in high intertidal rock pools, Giant's Causeway, Northern Ireland: preliminary observations.
Contemporary stromatolites are known from a variety of settings ranging from Antarctic dry valleys to hypersaline tropical lagoons. Their formation requires a source of calcium carbonate, binding by cyanobacteria and the elimination of other competing organisms by extremes of environmental conditions. In this paper we report the contemporary development of stromatolites in intertidal rock pools at the Giant's Causeway, Northern Ireland. The rock pools are high in the tidal frame and located on the landward margin of wide rock platforms that dissipate all but the most energetic waves. They are only infrequently inundated by marine waters but are fed by groundwater that emerges from surrounding high cliffs. Adjacent storm-swash deposits provide a potential source of calcium carbonate. The stromatolites occur in two distinctive settings. In one they are present as a thin covering close to the waterline in rock pools where their precipitation may be aided by wetting and drying of the associated microbial mats. Microscopic examination reveals a close intermeshing of cyanobacteria filaments and precipitated carbonate minerals. In a second setting, they occur on the base of rock pools as a semi-continuous covering. These have a much thicker development with the characteristic stromatolite growth forms forming mounds up to 3mm thick with multiple internal laminae. The occurrence of these structures is superficially similar to recently reported examples from rock pools in South Africa but their limited thickness requires explanation. This is either the result of changing environmental conditions that now favour stromatolite growth, or periodic cycles of formation and destruction driven by quasi cyclic changes in water chemistry.
Epifânio, B., Zêzere, J.L., Neves, M., 2013. Identification of hazardous zones combining cliff retreat with landslide susceptibility assessment.
Landslides are one of the main natural hazards which affect the coastal cliffs of Lourinhã council, located in Central Portugal. In this work, a methodology for hazard evaluation on coastal cliffs is presented, which combines the calculation of cliff retreat rates with landslide susceptibility assessment essential because landslide usually do not affect the cliff top. A landslide inventory was produced by aerial photo interpretation and a systematic field survey. The entire coastal stretch was split into 50m-long areas, resulting in 261 terrain mapping units. For each unit, 9 landslide predisposing factors were derived and classified. A predictive susceptibility model was developed using the Information Value method and the respective degree of fit was assessed using standard Receiver Operator Curves (ROC). Cliff retreat rates were calculated for a 60-year period using the ESRI′s Digital Shoreline Analysis System ArcGIS extension on a set of aerial photographs (which were manually geo-referenced and ortho-rectified) and a digital orthophotomap. Subsequently, predicted susceptibility data were integrated with the computed cliff retreat rates in a hazard matrix in order to create a map of the coastal cliff hazard. Cliff retreat rates ranged from 0.013 to 0.130m/yr and landslide susceptibility ranged from very high (4.2% of terrain unit) to low (0.8 % of terrain units). Approximately half of the study rocky coast is identified as being in a high hazard class. Thus, it is essential that hazard zones are considered for land use planning and management in order to reduce the probability of future incidents related to slope instability.
Giuliano, J., Godard, V., Dewez, T., Lebourg, T., Emmanuel Tric. and Marçot, N., 2013. Structural control on regional coastline orientations: example from South-eastern France
The morphology of rocky coastlines is the expression of the interaction between external forcings and the intrinsic rock mass properties, leading to a specific erosional response. Among these rock mass properties the contribution of structural discontinuities is still poorly understood. Nevertheless, recent studies suggest that geological structures may have a first order influence in controlling the coast morphology. Understanding how the structural pattern interacts with erosion processes is fundamental to assess the evolution of these environments. We propose a regional comparison between the orientation of rocky shorelines and faults segments in six different litho-structural units in the Provence and Côte d'Azur area (southern France). Our analysis reveals that in many of these sectors the dominant fault trend (E-W) is also present in the distribution of coastlines orientations. In some particular areas, a complex geological inheritance (Maures) blurs this apparent relationship between faults and coastal morphology. We conclude that, in our study area, the level of complexity of the structural setting seems to significantly control the nature and shape of the coastline.
Regard, V., Dewez, T., Cnudde, C. and Hourizadeh, N., 2013. Coastal chalk platform erosion modulated by step erosion and debris shielding: example from Normandy and Picardy (northern France)
Coastal platforms and cliffs compose an inter-dependant dynamic system. To understand how cliffed coast evolve, it is therefore crucial to quantify the magnitude and dependence of their processes. Here we question the role of erosion by waves at platform steps, often linked to lithological discontinuities. Along the French chalky coast of the English Channel, we determine, by comparison of aerial photographs at 23 yr interval that the mesoscale steps are retreating at a rate of ~2 cm/yr, ca. 10% cliff retreat rate. This corresponds to an average erosion rate of 0.32 ± 0.08 mm/a, quite uniform across the study area, suggesting that the geology has more of a control on erosion processes than the position in the tidal frame. In reality, erosion occurs only where platform surface is not shielded by debris fallen from the cliff. We study their size distribution (16% of the platform) and location and draw the conclusion that small falls are quickly erased by wave action while far reaching fans may cover the entire platform width. The peak shielding by fan debris occurs at a distance of ~40 m from the cliff. Step erosion by block quarrying is the process likely responsible for 20% to 100% of platform erosion.
Rohmer, J., Dewez, T., 2013. On the deviation of extreme sea-cliff instabilities from the power-law frequency-volume distribution: practical implications for coastal management. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1698–1703, ISSN 0749-0208.-->
Predicting very large sea cliff instabilities (extremes) are of primary importance for coastal risk management. Numerous works have addressed this problem based on the same paradigm: if events exhibit the same statistical properties across a broad range of sizes, the probability of very large extreme events can be evaluated by extrapolating the frequency-size distribution (traditionally represented by a power law model). We address this issue with an inventory of >8,500 sea cliff failures collated from repeated terrestrial laser scanning (TLS) surveys along a coastal chalk cliff in Normandy (France). The largest recorded event, a fault-bounded compartment of >70,000 m3, stands out as an extreme event. We use our inventory to revisit the techniques used to fit power-law distribution with a statistically robust weighted maximum likelihood estimator, which is much less sensitive to outliers. The estimator assigns a weight between 0 and 1 to observations according to their representativeness and rank order. We show that the low weight assigned to the largest sea-cliff instability is statistically significant (with p-value <1 %). Notwithstanding observation errors through the use of TLS, such statistical departure is discussed regarding two possible explanations: the moderate time resolution of the survey (every 6 months), and the physical mechanisms generating this large event. This issue motivates future work in high resolution coastal cliff monitoring, because the physical explanation might have strong practical implications for risk management, either in terms of frequency prediction of such extreme events or of identification of an informative precursor.
Vidal, M., Fornós, J.J., Gómez-Pujol, L., Palmer, M., Pons, G.X., Balaguer, P., 2013. Exploring rock coast bioerosion: rock fragment intestine transit time and erosion rates computation of the gastropod Monodonta articulata (Lamarck, 1822)
Coastal rock bioerosion research is well established. Otherwise there is the need to improve the way in which bioerosion rates are calculated. Since the findings of McLean (1967), it has been assumed that the dry weight of pellets collected after 24 hours provides an estimate of the amount of organism daily erosion. This is an assumption that relies largely on initial experimental procedures lacking any empirical ascertainment. This paper assess what is the transit time of the rock fragments through the intestine of the gastropod Monodonta articulata, and the implications of applicability of this temporal framework to the computation of a more precise estimation of the bioerosion throughout laboratory experiments. Our results suggest that for the gastropod Monodonta articulata, the major part of the eroded and ingested rock is defecated during feeding time. According to this, the confidence of bioerosion rates values calculated by means of faecal pellet collection based on 24-hour time frame can be concluded. Erosion rates for M. articulata activity in limestone rock samples have been estimated to range between 8.00 mg·ind−1·day−1 to 10.10 mg·ind−1·day−1.
Albuquerque, M., Espinoza, J., Teixeira, P., de Oliveira, A., Corrêa, I., Calliari, L., 2013. Erosion or Coastal Variability: an evaluation of the DSAS and the Change Polygon methods for the determination of erosive processes on sandy beaches.
There has recently been growing concern about issues related to erosive processes on sandy beaches and climate change in the scientific community. Several methodologies have been proposed in the worldwide literature to quantify coastline retreat on shorelines in an accurate way. It has been questioned whether these methodologies show the erosive process or the shoreline variability in a certain area. From this perspective, this paper aims at characterizing the accuracy of the Digital Shoreline Analysis System (DSAS) and the Change Polygon Method in the studies of regression on shorelines which are prone to erosion. Data collected by a GPS-RTK along Hermenegildo Beach, located in the south of Brazil, and the geo-referencing of satellite images enabled the outline of the shoreline in different periods with the use of both methodologies and the analysis of their accuracy. The DSAS showed good correlation among data; however, since it uses equidistant transects, it could not account for some features in the shape of crests or troughs in the area under study. The DSAS is based on the calculation of rates of statistical variations in a series of vector data that represents the shoreline. In order to correct those features that were not accounted for by the transects, more lines would have to be created so that a larger stretch of the area under study could be reached. The Change Polygon Method, based on the creation of polygons with lines from different periods, may be used to calculate the area of the region under study and compare it with areas from other periods. The calculated shoreline length led to the definition of the shoreline displacement in meters per year. The correlation was 13% (R2=0.131) in terms of reliability for the DSAS whereas it was 94% (R2=0.9418) for the Change Polygon Method, considering the same shorelines. Results showed that the Change Polygon Method is more reliable to evaluate variations in areas and shorelines by comparison with the DSAS. Choosing an efficient method to identify problematic areas with economic and social risks is fundamental to define strategies for proper management of places with erosive processes.
Aleman, N., Robin, N., Certain, R., Barusseau, J.-P. and Gervais, M., 2013. Net offshore bar migration variability at a regional scale: Inter-site comparison (Languedoc-Roussillon, France).
The Languedoc-Roussillon coastline is a large unit stretching out over 200 km of sandy low coast in a wave dominated environment. The nearshore is characterized by a quasi continuous system of double sandbar that displays a wide range of typology. The interannual sandbar dynamic was investigated using 2D bathymetric profiles and 3D LiDAR imagery. This study has allowed determining the sandbar systems affected by the Net Offshore Migration (NOM). At a regional scale, conditions necessary to NOM development depend on the sandbar morphologies (crescentic or straight), the wave energy and the associated coastal orientation (low or high energy, sheltered area), the coastal structures (harbour and coastal defences) and the nearshore sedimentary budget. The areas where the NOM occurs show cycle dynamic differences. This regional inter-site comparison highlights that nearshore morphology and bar parameters seem to influence the nearshore bar behaviour. Interaction between the nearshore slope, width of the bar zone and the migration rate control the NOM duration. The sandbar volume and the regional wave climate influence also the migration rate of the system. On the Languedoc-Roussillon coast, the sediment grain size does not appear to influence the seaward bar migration.
Bass, S.J., 2013. Characterising the ambient noise wave breaking environment on a sandy beach.
The interest in wave-generated noise is driven by the relationship with energy dissipation. Studies of deep-water waves show that the sound intensity due to wave-breaking correlates with the energy dissipation rate and it has been demonstrated that passive acoustic methods are a viable means of monitoring local wave breaking. Ambient noise measurements in the surf zone of a sandy beach are analysed for one four-hour measurement period over high water and the results are used to identify individual locally breaking waves from which dissipation rates are estimated. Estimates of wave energy dissipation agree broadly with those estimated using a weighted Rayleigh distribution to predict the breaking wave probability distribution. However, predicted dissipation rates displayed greater variability and an overall lower net dissipation over the measurement period when compared with dissipation estimated using the measured breaking wave fraction.
Birrien, F., Castelle, B., Dailloux, D., Marieu, V., Rihouey, D. and Price, T.D., 2013. Video observation of megacusp evolution along a high-energy engineered sandy beach: Anglet, SW France.
We present an 18-month period of video monitoring of both the nearshore sandbars and the megacusps at Anglet Beach, SW France. The study site covers a 2-km long stretch of beach that is constrained to the North by a groin that extends 400 m seaward. The beach is high-energy intermediate, mostly double-barred, with a steep beach face (~1/10) favouring the formation of cusps at a large range of lengthscales, from beach cusps (O(10 m)) to megacusps (O(100 m)). A megacusp is systematically observed against the groin as a result of the persistent presence of a topographic rip. Further away from the groin, about 4–5 megacusps are typically observed. The shoreline dynamics are strongly controlled by the geometry of the surfzone sandbar. In-phase shoreline-sandbar coupling was commonly observed, that is, megacusps in the alignment of the rip channels and seaward bulges in the shoreline facing the surfzone sandbar horns. Megacusps at Anglet Beach have a typical cross-shore amplitude of O(10 m). During a severe storm with significant wave heights over 7 m, a very erosive megacusp (hotspot) formed in the alignment of the rip channel. Prior to this storm, a seaward bulge in the shoreline was observed in this location. Accordingly, 40 m cross-shore variation change in shoreline position at this location was the signature of megacusp dynamics only. This hotspot was systematically observed at the same location during 7–8 months after the storm event, before the fair weather conditions in summer resulted in an overall accretion of the beach. Megacusps were smoothed out during rapid alongshore migration of the sandbar or for high-energy wave conditions. In addition, the evolution of the alongshore-averaged shoreline position shows the exact opposite trend as that of the alongshore-averaged sandbar position, yet with less pronounced cross-shore variations. Overall, our results highlight once again the strong links between shoreline and surfzone sandbar dynamics.
Botero, C., Anfuso, A., Williams, A.T and Palacios, A. 2013. Perception of coastal scenery along the Caribbean littoral of Colombia.
Scenic evaluation is an important tool for coastal classification and management, as results obtained from numerous enquires carried out in Europe and USA showed that it is one of the top five parameters in beach choice, the others being safety, facilities, water quality and litter. The specific ranking of each one of the previous parameters ranges from place to place, scenery achieving greatest importance in the UK and USA (first and second place, respectively) and less importance in Malta, Turkey and Spain. In UK, the most important aspects of coastal scenery are historic features (hill forts, lighthouses, etc.), absence of noise, cliff height and beach type (e.g. sand). In Turkey, beach users give more importance to the absence of sewage and litter, water colour and quality, the absence of buildings and vistas of far places. In order to determine the importance given by beach users in the Caribbean coast of Colombia to coastal scenery and to its different aspects, 435 enquires were carried out at eight beaches in the provinces of La Guajira, Magdalena, Atlántico and Bolívar during 2011 and 2012. Results obtained indicated that there was circa 50% difference between the Colombian checklist, as against the one utilised in Europe and the USA. The main differences related to vegetation cover, cliffs, rock platforms, dunes, tidal range, built-non built environment, sky line and noise. The importance given to water clarity, also observed in previous studies carried out in Mediterranean beaches, is linked to the fact that local and national tourists came to the beach for swimming and/or sun, as virtually every beach user enters the sea. Lastly, the importance given to vegetation cover (especially in urban beaches where the vegetal cover consists of planted palm trees), is not really linked to their landscape value but to their usefulness in providing shade.
Bulhões, E., Fernandez, G.B., Rocha, T.B., 2013. Morphodynamics of Embayed Beaches. Case Study in Cape Buzios, Rio de Janeiro, Brazil.
Cape Buzios is a balneary touristic county located 180 km east of Rio de Janeiro city, Brazil. The geological site is composed by metassedimentary and metavolcanic rocks originated from a Cambrian and Ordovician (530–490 Ma) collisional event named Buzios Orogeny. The main characteristic of Cape Buzios is distinct structurally controlled beaches. The objective of this paper is to present results of morphodynamics of embayed beaches exposed to distinct wave's directions and relate it to the morphological response of beach profiles. Thirteen different beach profiles were monitored during four years in seven embayed beaches using standard topographic methods, resulting in over 250 beach profile data. Wind and wave data statistics; morphodynamic and embayment scale parameters; equilibrium profiles; closure depth; and planform stability were also calculated. Results led to the identification of three different morphodynamic conditions. The first two are low energy reflective and high energy intermediate beaches that are morphologically stable. In the first case beaches are narrow and equilibrated with their transversal profile. Closure depths vary from 3 to 6 meters. In the second case beaches are overfilled with sediments which even in high energy conditions permit rapid morphological recovery, closure depths are up to 20 meters. The third morphodynamic condition refers to unstable beaches that also have two different characteristics: one group of beaches presents permanently erosional profiles, while the other group presents episodic erosional profiles. The differences were in the range of exposition to higher waves and the volume of nearshore sediments available. Estimated maximum wave heights of 1,3; 2,4 and 5,4 meters can be respectively correlated for each one of the morphodynamic conditions described above.
Castelle, B., Dubarbier, B., Tissier, M., Bonneton, P., Conley, D.C., Ruessink, B.G. and Masselink, G., 2013. Testing numerical hydrodynamic and morphodynamic models against BARDEX II Experiment data sets.
The hydrodynamics on barred beaches and mechanics of sediment transport related to sandbar migration, berm formation/destruction, barrier crest dynamics and washover deposition are extremely complex. At this time, process-based models encompassing all these processes are non-existent. Among other shortcomings, the lack of existing intensive high-frequency full-scale data limits the range improvement and validation of nearshore process-based models. In June 2012, the large-scale Barrier Dynamics Experiment (BARDEX II) was performed in the Delta Flume, providing new datasets for rigorous testing of existing hydrodynamic, groundwater and morphodynamic models and further assisting their development. Three types of models are expected to be applied and further improved: (1) the short-wave averaged surfzone beach profile evolution models 1DBeach and UNIBEST-TC, (2) the short-wave averaged and infragravity-wave resolving XBeach model that addresses morphological changes of the nearshore area, beaches, dunes and backbarrier during storms including cross-barrier groundwater fluxes and (3) the short-wave resolving hydrodynamic models SURF-GN and SWASH. In this contribution, we present the application of three of the five models. 1DBeach is applied to a morphological sequence characterised by onshore and subsequent rapid offshore sandbar migration for time-invariant wave forcing and falling tide. XBeach model is applied to a rising tide sequence characterized by a rapid shoreline retreated and overtopping and overwash processes. SURF-GN is applied to a high tide run with occasional overtoppings. All these model applications are described and model skills are qualitatively assessed. Guidelines for future model improvements and validation on BARDEX II dataset are further discussed.
Costa, R.M. da, Matos, J.B., Pinto, K.S.T., Pereira, L.C.C., 2013. Phytoplankton of a dynamic Amazon sandy beach
The present study was developed to characterize the structure and the temporal variation of the phytoplankton of the surf zone of Atalaia beach (Pará, Brazil) and to investigate the effect of certain environmental variables on this community. Nyctemeral sampling was carried out in November/08, March/09, June/09 and September/09. Ninety- eight taxa were identified. The diatoms dominated the local microphytoplankton with the species Coscinodiscus perforatus Ehrenberg, Dimeregramma minor (Gregory) Ralfs, Ditylum brightwellii (West) Grunow and Odontella sinensis (Greville) Grunow having the highest frequency of occurrence and relative abundance. The maximum phytoplankton density was 1,723 ± 257 ×103 cell L−1 in September/09 (F=18.8; p <0.05), while biomass (chlorophyll-a content) was significantly higher in November/08 (U= 0.00; p <0.05). The highest densities of D. minor in September resulted in the lowest observed diversity and evenness. Cluster Analysis showed the formation of three groups, with 55% similarity. The separation of the groups was influenced primarily by the seasonal distribution of samples. Overall, rainfall and consequently variation in salinity showed a strong influence on local phytoplankton composition, density and biomass. Furthermore, the strong local hydrodynamics, as well as the action of the winds and currents promoted the ressuspension of tychoplankton species that characterized the structure of the local phytoplankton.
Deidun, A., Gauci, R., Schembri, J.A., Šegina, E., Gauci, A., Gianni, J., Gutierrez, J.A., Sciberras, A. and Sciberras, J., 2013. Comparative median grain size assessment through three different techniques for sandy beach deposits on the Maltese Islands (Central Mediterranean)
It is estimated that sandy beaches cover only 2.2 per cent of the Maltese coastline. Although small in size, Maltese pocket beaches exhibit complex geomorphological interactions. A granulometric analysis of Maltese beach deposits may thus shed further light on the understanding of these interactive processes and provide baseline information on how beach sediment size may relate geo-spatially and morphometrically. Surface (0-10cm) sand samples were collected from ninety sandy beaches in Sicily, circum-Sicilian islands and the Maltese Islands. The median grain size of these sediment samples was assessed through three different techniques: the conventional sieving technique, observation through stereo microscopy and through image processing. The two primary objectives of such work were firstly, to construct a repository of median grain size values for the entire stretch of Maltese sedimentary coastline (the first study ever to be done on such a comprehensive spatial scale), and secondly, to evaluate the degree of concordance between the three techniques. The highest Pearson correlation value (0.90) was recorded for the sieving-scanning match, although in many cases differences were large enough to result in a different sediment type classification. The highest level of agreement between the scanning and sieving technique was registered for the medium-fine (1.5–2.5phi) and very coarse categories (−0.5–0.0 phi). Median particle diameters measured through microscopy were those which diverged most from those of other techniques. This maybe due to the relatively small number of sediment grains which were analysed within such a technique.
Dubarbier, B., Castelle, B, Marieu, V and Ruessink, B.G., 2013. Numerical modelling of pronounced sloping beach profile evolution: comparaison with the large-scale BARDEX II experiment .In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)
Barriers and sandbars are ubiquitous natural coastal features, whose variability often determines nearshore morphological evolution. Wave-dominated beach profile evolution results from the interaction between wave non-linearities, wave-breaking induced turbulence, undertow, infragravity motions and swash processes. To explore each of these contributions to the sediment transport, the full-scale Barrier Dynamics Experiment (BARDEX II), performed in the Delta Flume in June 2012, provides a new dataset for the rigorous testing of the performance of beach profile evolution models in the case of steep beaches. This new experiment will improve our knowledge on (1) swash zone processes, including infiltration and exfiltration of water into the sand and subsequent groundwater table response, (2) bore-generated turbulence inducing suspend sediment transport, (3) surfzone sandbar dynamics and (4) overtopping/overwash impact on barrier dynamics. This study aims at testing the ability of the process-based beach profile model 1DBeach in the case of a steep beachface and a predominance of plunging breakers. In this context, we tested the model with a morphological sequence characterised by onshore and subsequent rapid offshore sandbar migration for time-invariant wave forcing and falling tide. A simulated annealing algorithm is used to calibrate the model. In this paper, we discuss the model configuration and associated results, as well as the need of intensive high-frequency full-scale data to further develop and improve process-based models.
Gómez-Pujol, L., Orfila, A., Álvarez-Ellacuría, A., Terrados, J. and Tintoré, J., 2013. Posidonia oceanica beach-caster litter in Mediterranean beaches: a coastal videomonitoring study.
Mediterranean nearshore sandy and rocky bottoms are colonized by the endemic reef-building seagrass Posidonia oceanica. This species loses leaves in autumn that form large litter patches in the surf zone and huge litter banks on adjacent beaches, resulting in wedge and layered structures of few centimetres to several meters in thick (banquettes). Some authors pointed the importance of those banquettes for the protection of sandy beaches because they dissipate wave energy. By contrast other authors state that this effect is almost negligible. This work deals with the role of Posidonia oceanica accumulations in Mediterranean beach morphodynamics. By means of coastal video-monitoring and wave records we assess the marine conditions related to the formation and destruction of banquettes and evaluate their role in the protection of two sandy beaches (Cala Millor and Son Bou, Balearic Islands). Results indicate that banquettes are common beach features at the study sites although they are not persistent and experience complex construction and destruction dynamics throughout the year. Two different types of banquette construction can be differentiated over the year: one related to the reworking of older seagrass beach cast by alongshore currents and a second as a response to the incorporation of new volumes of dead leaves after energetic winter storms (Hs ~2 to 3 m). In both cases, seagrass cast accumulations are continuously built up and destroyed and rarely persist before the arrival of new sea storms. Therefore, at least for semi-enclosed sandy beaches, the protection role of seagrass banquettes should be reconsidered.
Goulart,E.S., Calliari, L.J.,2013. Medium-term morphodynamic behavior of a multiple sand bar beach.
Cassino beach, located in southern Brazil, is a very fine sand beach with morphodynamic stages ranging from dissipative to intermediate. This beach can display up to three sand bars which are active during high energy events. Since the beach is located in a microtidal area, flood events are mainly caused by storm surges which can reach 1.8 m. During such events the highest rates of beach erosion are observed. A series of six years (from March 2005 to February 2011) of data from video images have been used to study the nearshore morphodynamic behavior. Daily data of sandbars and waterline position were obtained from these images. The generated data was analyzed in order to recognize flood events patterns as well as patterns of beach morphodynamic both during flood events and during normal conditions. Forty seven flood events were identified, 53% during winter, 24% during autumn, 17% during spring, and 6% in the summer. The average duration of events is 1.5 days. During this period, the whole system is migrating offshore in a rate of 9 m/year. Wavelet analysis showed a gradation of frequencies that govern the variability of the surf zone features. Closer to the beach high frequencies processes (associated with tides and meteorological forcing) have larger influence than further offshore, where longer processes gain importance.
Guerreiro, J.S., Ranieri, L. A., El-Robrini, M., Vila-Concejo. Seasonal changes of a dynamic macrotidal beach: Case Study of Marieta beach(Amazon Coast/Brazil)
The Amazon Atlantic Coast is a very dynamic area due to the large discharge associated to a large network of rivers that include the Amazon River. Many of the beaches in this area are located within the area of influence of macrotidal range. There is a large sediment availability that creates extensive tidal flats. Waves are moderate with average offshore of 1.8m. The area has a tropical climate with two seasons, rainy and dry, and is under influence of moderate SE/NE trade winds. This paper presents topographic and hydrodynamic data from one of these beaches, Marieta Beach, and shows that while it undergoes severe erosion during the rainy season, accretion and recovery occurs during the dry season. Erosion seems to be associated to the large river discharge in the rainy season (10 3 to 10 4 m3/s−1), high water levels coupled with strong ebbing currents that remove the sediment from the beach. The beach accumulates large volumes of sediment during the dry season (averaging 15.2 m3); the processes that drive sediment transport are not clear but given that onshore winds occur during this period, it is hypothesized that locally wind- generated waves are capable of transporting sediment back to the beach. Seasonal behavior in this case is associated to the tropical seasonality of the rivers instead of traditional storm/fair weather conditions cycles that are often found in the literature.
Idier, D., Castelle, B., Charles, E. and Mallet, C., 2013. Longshore sediment hindcast: spatio-temporal variability along the SW Atlantic coast of France !
The Aquitanian coast (SW France) is exposed to high-energy waves, and subject to an overall shoreline erosion of 1 to 3 m/year. Engineering practices in this area requires the knowledge of longshore sediment fluxes. The reference values of direction and variability have been estimated 33 years ago with data available at that time. More recent estimations have been done on limited area and time span. The present study aims at: (1) updating and discussing the longshore sediment flux on this coast, (2) comparing the longshore drift spatial variability with measured shoreline evolution, (3) analyzing the interannual variability, in comparison with NAO indexes. Using a recent wave hindcast spanning the period 1958–2001, and the Kamphuis (1991) formula, the obtained gradients in longshore drift appear roughly consistent with the shoreline evolution and previous estimations of residual sediment fluxes. However, the estimated northward oriented fluxes are smaller in the present study than in the 33 year old reference study. The analysis shows a strong interannual variability, slightly smaller than the longshore variability. The interannual variability is not uniform along the coast. The northern section seems to be correlated with NAO indexes. Further analyses are required to better understand the temporal variability of the longshore sediment fluxes.
Khoury, A., Jarno-Druaux, A., and Marin, F., 2013. Experimental simulation of sandy beaches under waves and tides: hydro-morphodynamic analysis Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1791–1796, ISSN 0749-0208.-->
Numerous studies have been carried out on sandy beach morphology; however, the physical processes which govern beach morphodynamic are still not well understood, despite the significance of this subject in view of the direct applications for coastal erosion. The present work brings a contribution to the study of these processes from well controlled tests carried out in a 10-m-long and 0.49-m-wide wave flume with macro – and mega-tidal regime simulations. The tests were carried out with very fine or fine sand of relative density s=2.65. The incident waves and the free surface in the shoaling zone were measured with resistive probes. The wave breaking height and the free surface in the swash zone were recorded with an optical method. The temporal evolution of bottom profiles was obtained using an acoustic method. Intertidal bars were generated; such bars were previously not observed in physical modeling to the authors' knowledge. Present experimental results are compared with field observations. Formation processes of intertidal bars are analyzed; we show in particular the significant effect of the relative tide range, of waves asymmetry, and of subtidal bars on these processes. Small local variations of the beach profile in the surf zone exhibit significant outcomes on the runup.
Kuriyama, Y. and Banno, M.., 2013. Numerical investigation of the influence of the enhancement of cyclones on long-term shoreline movement
The enhancement of tropical and extratropical cyclones caused by global warming is expected to induce morphological changes in the nearshore zone. Hence, the influence of the increase in offshore wave energy flux Ef due to the enhancement of cyclones on long-term shoreline movement on the Hasaki coast of Japan was examined using a numerical model for predicting the shoreline changes caused by cross-shore sediment transport. The shoreline movements during a 100-year period were predicted with 4-month intervals by increasing the means and/or standard deviations of Ef during the 4-month seasons. Under each wave condition, the predictions were implemented 1000 times with Ef estimated using a Monte Carlo method. The prediction results showed that the shoreline retreated 18 m with 20% increases and 33 m with 50% increases in both the means and standard deviations of Ef in the 100–year period. The increases in both the means and standard deviations of Ef during the periods from May to August and from January to April influenced the shoreline retreat most and least, respectively. This was probably due to the nonlinear relationship between the shoreline change rate and Ef.
Miles, J.R., 2013. Wave shape effects on sediment transport.
Waves approaching the shoreline become skewed in the shoaling region and asymmetrical in the surf zone. The different velocity distributions associated with these waves affects sediment suspension, transport, and ultimately beach morphology evolution. An intra-wave model of sediment suspension was constructed in which a given velocity time series is used to predict sediment concentrations based on a Bagnold type u-cubed model for stirring, balanced by settling. The model was validated against field data gathered at Sennen (Cornwall, UK), where simultaneous high frequency (8 Hz) measurements of sediment concentration and velocity were made in the surf zone of a macro-tidal, intermediate beach. The model was run for a range of hypothetical velocity time series associated with different wave shapes, grain sizes and wave periods. Results indicate that asymmetric waves, skewed waves, and skewed-asymmetric wave velocity profiles lead to increased wave-averaged suspended sediment concentrations, and increased onshore transport rates when compared to sine waves of similar velocity range. Skewed-asymmetric waves give rise to almost twice as much transport as skewed or asymmetric waves alone. Finer grained sediments, and shorter period waves give higher mean sediment concentrations and transport rates. In conditions when sine waves result in little net transport (coarse grains or long wave periods), the evolution of wave shape to skewed and/or asymmetric can directly give rise to a net onshore transport. Wave shape (sine, skewed and/or asymmetric) is therefore identified as a key controlling variable in predicting suspended sediment concentrations and transport rates in the nearshore.
Murray, T., Cartwright, N., Tomlinson, R., 2013. Video-imaging of transient rip currents on the Gold coast open beaches.
Transient rips vary in location and occurrence making them hard to predict, and unlike topographically controlled, fixed or semi-permanent rips, they are believed to be controlled by surf zone hydrodynamics rather than beach and surf zone morphology. This paper reports on the first video analysis of transient rip behaviour in the Southern Hemisphere. Transient rips were identified from a high camera located approximately 100 m above mean sea level at Narrowneck, Gold Coast, Australia. Transient rip occurrence, duration and flow behaviour were identified from the video and occurrence was correlated with environmental factors including beach state, wave, tide and wind characteristics. Transient rips were found to display a mushroom cloud rip head and a narrow trailing rip neck consistent with characteristics often displayed by topographically controlled rips. Transient rip events were characterised by short life-spans (30 – 236 s) and low temporal frequency, but high temporal variance, occurring for only 0.52% of the time in the video. Around 66% of transient rip events identified occurred when the beach was generally alongshore uniform in a shore-attached terrace state. Transient rip occurrence was also found to be significantly greater on the ebb tide as opposed to the flood tide and when wave breaking was absent on the outer bar. There was a lack of a clear correlation between averaged wave and wind conditions and transient rip formation. Current and future study is focussing on the effects of wave groupiness and sea state on transient rip occurrence, spacing, duration and intensity.
Oliveira, F.S.B.F. and Contente, J., 2013. Scale effects in numerical modelling of beach profile erosion.
The beach profile morphodynamic processes can be relatively well reproduced in large scale physical models. However, the cost associated to their use makes this methodology not always practicable. As alternative, it is desirable to explore and apply smaller scales laboratory infrastructures with confidence, despite the different scaling laws, that is, the impossibility to simulate all relevant variables in correct relationship to each other. The combination of physical and numerical modelling can be a methodology to improve the required confidence (HYDRALAB III European Programme). Scale effects in a numerical process-based beach profile model, applied to simulate beach profile evolution under erosive wave conditions, were investigated in the present study. The numerical model was applied at laboratory and prototype scales, first with the default settings and then calibrated. Its performance was evaluated using the Brier Skill Score. The numerical results of the profile evolution in both scales were compared after reducing the results from the prototype scale to the laboratory scale. The profile erosion prediction was overestimated in the laboratory scale and underestimated in the prototype scale. Despite the calibration parameter that causes the largest modifications of the beach profile being the same in both scales, the Gamma2 wave parameter, the most efficient parameter was different. For most of the calibration parameters, the value for the best case was not coincident in both scales. It was concluded that there are scale effects using the Litprof model.
Pereira, L.C.C., Vila-Concejo, A.and Short, A.D., 2013. Influence of subtidal sand banks on tidal modulation of waves and beach morphology in macrotidal beaches.
Amazon beaches are controlled by large tidal ranges, strong tidal currents and an ample supply of sediments, which create subtidal sand banks that modulate wave energy on the shoreline. Given this, the objective this study was to study the effects of tidal modulation of waves on spatial and temporal beach morphodynamics. This paper presents morphological and hydrodynamic data from three beaches on the Amazon coast of Brazil. Data was taken between November, 2008 and October, 2009. This study has two time scales: short term intensive campaigns with hydrodynamic measurements and topographic surveys and medium term measurements that refer to climatologic and offshore wave data obtained from National Institutes. For the analyses considering the ebb tide and flood tide conditions we have found higher RTR modal values and lower Ω modal values during the ebb tide periods, mainly in the most sheltered beach (higher influence of sand banks), showing the influence of tidal modulation. On the more exposed beach (lower influence of sand banks), a greater influence of wind-wave contributed to a similar pattern among the ebb and flood tide phases, prevailing low tide bar and non-barred dissipative characteristics. On the most sheltered area, the tidal processes dominate maintaining ultradissipative beaches and tidedominated tidal flat. On the macrotidal Amazon beaches tidal elevation and subtidal sand banks modulate the wave energy – during low tide, the waves break offshore on the sand banks and they only start to propagate over the banks when tide is increasing, reaching the maximum wave energy during high tides.
Pérez, F., García, M., Castillo, A., Abogado, M.T. and Duarte, J.F., 2013. Tools to characterize sandy beaches: towards integrated management of Venezuelan beaches
In Venezuela, the coastal public domain constitutes a priority area to develop management strategies. To achieve this goal an Inventory and Characterization of Sandy Beaches has been initiated among other actions. This project comes from the need to generate a systematic database, in order to provide inputs for sustainable management and coastal resource recovery. This will set bases for the design of Strategies for Sustainable Management of Sandy Beaches in the country. The methodology was designed by a multidisciplinary team and validated by the Working Committees of Coastal Zones, which includes the participation of all institutes with interests in this space, universities and communities. A concept of sandy beaches had been defined, considering national and international references, adapted to the geography of the country. The methodology includes three tools: 1) Form, 2) Technical Manual and 3) Field Guide. The Form serves as a checklist easy to handle by planners, managers, students and communities. The Technical Manual provides detailed knowledge of each component analyzed in the form. The Field Guide shows a series of pictures and graphs illustrating the variables, in order to facilitate identification and evaluation of each component. A process of regional training began in 2011, conducted by theoretical and practical workshops. By April 2012, 368 persons have been trained and 365 sandy beaches have been characterized nationwide. All these activities have been developed under the premise of the National Plan of Integrated Coastal Zone Management of Venezuela, “a space with its own identity”
Phillips, R., Vincent, C.E., Bell, P.S., Dolphin, T., and Bacon, J., 2013. Use of GPS and X-Band Radar to track tidal currents around the shore parallel breakwaters at Sea Palling, Norfolk, UK
Sea Palling on the East coast of the UK has a series of 9 shore parallel rock breakwaters. The numerical model TELEMAC2D has been used to simulate tidal currents around the system to assess the tidal contribution to sediment budgets and transport pathways. Numerical simulations are particularly useful for identifying the important processes involved in a complex system such as these breakwaters and understanding how the breakwaters might effect the local coastal region. Models are classically evaluated using a number of measurement stations to calibrate and then check it is giving realistic results. It is important to assess both the spatial and temporal performance of a model, but this is difficult with a model having tens of thousands of nodes, based on only a few discrete locations. This paper presents a method using Lagrangian data to assess confidence that can be applied to model performance. Measurements were made by deploying drogues tracked by X-band radar or GPS receivers throughout the breakwater system during calm “no wave” and “no wind” conditions to ensure that only tidal effects were measured. Modelled deployments were made at coincident times and locations for comparison and model performance statistics were calculated. Evidence of a number of features predicted by the model were found, giving confidence to its performance. Radar drogues are cheap to make and data capture onshore reduces the risk of data loss. GPS drogues can be used in a wider spatial area, however their onboard data storage requires drogue retrieval for data download.
Pinheiro, S.C.C., Magalhães, A., Costa, V.B. da, Pereira, L.C.C. and Costa, R.M. da, 2013. Temporal variation of zooplankton on a tropical Amazonian beach.
To assess the spatial and temporal variation in zooplankton populations at Ajuruteua Beach, northern Brazil, monthly samples were taken between August, 2004, and July, 2005, at three fixed stations, during the spring (flood/ebb) tide. The zooplankton community was characterized by the absence of any significant spatial or seasonal variation in density, diversity or evenness. However, density was significantly higher during the ebb tides, with mean values ranging from 4,967±670.0 ind.m−3 in July (flood tide) to 38,213±15,157 ind.m−3 in April (ebb tide). A similar tidal pattern was recorded for the density of copepods. The dominant copepod species were Euterpina acutifrons (47.0±30.5 to 18,313±2,431 ind.m−3) and Paracalanus quasimodo (420.0±60.0 to 11,260±7,203 ind.m−3) and, together with Oithona hebes and O. oswaldocruzi, were responsible for the peaks in zooplankton density recorded in April. Monthly zooplankton diversity (1.8±0.2 to 3.0±0.1 bits.ind−1) was relatively high overall, whereas evenness varied from 0.4±0.0 to 0.8±0.0, with both indices presenting significantly lower values in November. The absence of any significant seasonal trend in total zooplankton during the present study may have been related to atypical precipitation patterns during the study period, when surface waters were abnormally warm (~1.5°C). Overall, zooplankton community structure at Ajuruteua Beach was indirectly related to the local rainfall regime, which affected the physical, chemical, and biological parameters of the water, influencing the temporal dynamics of these organisms.
Pupienis, D., Buynevich I.V., Jarmalavičius, D., Žilinskas, G., and Fedorovič, J., 2013. Regional distribution of Heavy-mineral concentrations along the Curonian Spit coast of Lithuania
Heavy-mineral concentrations (HMCs) in coastal sands serve as important indicators of hydrometeorological and sedimentological conditions. Along the southeast Baltic Sea coast, quartz- and feldspar-rich sands contain variable amounts (1–8%) of heavy minerals, such as garnet, rutile, zircon, magnetite, ilmenite, hornblende, and other accessory minerals. Their concentrations are found along the Baltic Sea coast of the Curonian Spit, a 98-km-long barrier divided between the Russian Federation (47 km) in the south and the Republic of Lithuania (51 km) in the north. The open sea beach sites range from 25 to 80 m in width and are backed by 5–16 m height foredunes. To examine the patterns in HMC distribution, a total of 303 surface sand samples were collected from the middle of the beach, foredune toe, and stoss slope at 500 m intervals along the entire length of the Lithuanian section. To characterize the relative concentrations of heavy minerals (especially ferrimagnetic), a Bartington MS3 field scanning sensor was used for rapid and effective measurements of low-field volume magnetic susceptibility (MS). Along the Baltic Sea beach, in-situ MS values of κ< 50 μSI of background quartz-rich sands contrast with κ > 150 μSI in surface HMCs. On the beach, MS averages 38 μSI, whereas on the foredune toe and stoss slope they decrease to 33 and 26 μSI respectively. Furthermore, alongshore variations in beach HMC characteristics follow a cyclic pattern with a wavelength of approximately 10 km. This pattern is likely related to wave runup during major storms, whereas on the foredune toe and stoss slope, HMCs reflect the secondary reworking by aeolian processes. Along the sectors with higher MS, coastal erosion processes dominate (Pervalka-Nida), whereas low values generally correspond to regions of sand accumulation (Kopgalis-Pervalka). Therefore, surficial HMCs have the potential for characterizing long-term patterns of regional distribution of hydrodynamic energy along drift-aligned sandy coasts.
Roig-Munar, F.X., Mir-Gual, M., Rodríguez-Perea, A., Pons, G.X., Martín-Prieto, J.A., Gelabert, B. and Blázquez, M., 2013. Beaches of Ibiza and Formentera (Balearic Islands): a classification based on their environmental features, tourism use and management,
In order to define their character a total of 100 beaches of Ibiza (76) and Formentera (24) are analyzed on the basis of 35 variables of beach use, state and management. We take as a reference a primary classification where three types of beaches have been considered; urban beaches (A), semi-natural beaches with urban features (B), and natural beaches (C). Departing from this scenario, and taking into account the identified variables, statistical analysis (Cluster and PCA analysis) have been done in the sense of identifying the current state of each beach and the differences among them. Currently many of the beaches of Ibiza are urban beaches (A). Furthermore the results suggest a potential trend that some of natural beaches (B-C) can become to A type in the next future. Understanding this classification, and also the recent history of the management applied in the study units, allow predicting trend scenarios. In this sense, management changes should be proposed in order to improve their current situation, and drive them toward a better conservation status.
Rollnic, M. and Medeiros, C., 2013. Application of a Probabilistic Sediment Transport Model to Guide Beach Nourishment Efforts
This study focused on establishing the probability of different sediment grain size be transported by coastal currents, as a prognostic tool to guide nourishment efforts at a coastal section near Recife, NE-Brazil (UTM 9105000-9089969N; 0297000-0289227E). The SisBahia hydrodynamic module FIST3D was applied linked to the Lagrangian-Probabilistic Transport Module over a 27km-long coastal band from 0 to 17m isobaths. The bathymetry and sedimentary coverage was characterized in a 200m grid. Input and calibration data were originated from a 3-years field work comprising 40 stations and considering seasonal variability. Data base included instantaneous current measurements, current, tide and wave time-series and CTD profiles. A finite-element grid (876 quadratic elements; 3703 nodes) was generated and twenty one depth levels defined through the water column. Simulations were performed with a 50s time-integration intervals, resulting an average 4.57 Courant number. Dry and rainy season scenarios under neap and spring tides were simulated with good agreement between simulated and in situ data. Simulation for each scenario was conducted over a 10-days period, and the probability of the different currents intensity near the bottom relative to its ability to move the various sediments fractions were mapped. Simulation indicated a high potential for sediment transport in the area under more severe erosion. Here current intensification was verified at both seasons and during neap and spring tides. Fine sand have a 90% probability of being transported by local currents, medium and coarse sands a probability of 80% and very coarse sands a probability of 60%.
Silva, R., Veloso-Gomes, F. and Pais-Barbosa, J., 2013. Morphological Behaviour of Costa da Caparica Beaches Monitored during Nourishment Operations.
Coastal erosion is a common problem along sandy shores in Europe, a result of its dynamic nature, anthropogenic influences and the effects of climate change. The coastal stretch Cova do Vapor-Costa da Caparica, located south from Tagus River, evidences chronic erosion problems since the 60's. It was necessary to construct a series of defence structures that more or less stabilized the beaches for nearly 30 years, although subjected to occasional overtopping and to increasing urban pressure and tourism. A worsening of the erosion situation from the winter of 2000/01 required a new intervention, which was envisaged in several phases, including the rehabilitation of the structures and the annual nourishment of the beaches. The nourishment operations were accompanied by a topo-hydrographic monitoring program, which complemented a database for the time period between 2001 and 2010. In this paper, the morphological behaviour of the sector is investigated making use of these data. A procedure for the analysis of its volumetric evolution is presented, following the test of different methods for volume variations estimation. Some conclusions about the behaviour of the sector and the lifetime of the nourishments are drawn, together with recommendations concerning topo-hydrographic monitoring. A morphological model and a medium to long-term coastline change model are being implemented at the site. Their implementation is intended to support the test, cost-effectiveness analysis and selection of interventions, for this site or others to which the analysis procedure may be exported.
Stokes, C.H., Russell, P., Conley, D., Beaumont, E., Greaves, D., 2013. Exploring Monthly To Seasonal Beach Morphodynamics Using Empirical Orthogonal Functions.
Empirical Orthogonal Function (EOF) analysis is a statistical method that can separate out the dominant modes of change in beach topographic data. Here the method is applied to four years of monthly intertidal survey data from Perranporth beach (Cornwall, UK), a predominantly dissipative site, which exhibits episodic low tide bar-rip morphology. The aim is to understand the main morphodynamic changes by studying only the dominant EOF patterns. Gridded data from 48 surveys was analysed and two statistically significant EOF modes were identified. The primary EOF (EOF1) has been interpreted as a seasonal ‘beach volume function' and shows that alongshore-uniform gains and losses of sediment, predominantly from the mid intertidal region, account for almost 50% of all the variability that occurs in the data set. This occurs with an annual periodicity, and the increasing trend in the temporal signal has been associated with the long term (∼years) increase in volume that the beach is experiencing. The second EOF (EOF2), has been interpreted as the ‘dominant rip function' and indicates that the second most dominant mode of change (∼11% of the total variability) involves the development of a recurring low-tide rip channel accompanied by a steepening of the beach and an increase in 3D structure.
Tătui, F., Vespremeanu-Stroe, A. and Preoteasa, L., 2013. The correlated behavior of sandbars and foredunes on a nontidal coast (Danube Delta, Romania)
Coastal foredunes, shoreline and nearshore sandbars compose one large-scale interactive morphological system. Although the variability of these coastal features and their connection to environmental factors have been the focus of many analyses, the direct interactions between them are yet poorly identified, especially for natural nontidal coasts. This paper presents the preliminary results regarding the correlated behavior of the foredunes, shoreline and sandbars in a multi-bar, low-lying deltaic coastal zone, based on six years of seasonal bathymetric and topographic surveys. The analysis shows that, at the multiannual scale, there is a good correlation between the morphometric parameters (volumes and widths) and behaviour (spatial and temporal) of sandbars and foredunes, especially along the accumulative and stable sectors of the study area. Good correlation of these sectors is expressed by the fact that the two entities are interdependent and they present similar variability. The weak correlation identified along the erosive sector is probably due to the significantly lower variability of the foredunes when compared to that of the sandbars. This could reflect the strong influence of the Sf. Gheorghe mouth bar and the pattern of sediment availability, wave climate and longshore sediment transport characteristics along the three sectors of the study area with different shoreline dynamics.
Thorpe, A., Miles, J., Masselink, G., Russell, P., Scott, T., Austin, M., 2013. Sediment Transport In Rip Currents on a Macrotidal Beach
Rip currents are offshore-directed flows in the surf zone that may be responsible for significant offshore transport of sediment. In this study high frequency surface elevation and current velocity data were collected alongside suspended sediment concentrations in a rip channel on a high energy, macro-tidal beach. At low tide (water depth over the rip channel (h) = 0.9 m), when the rip current was active (maximum offshore directed flow = ~ 0.4 m/s), net suspended sediment transport was directed offshore, and 88% of the flux was due to the mean flow component. The rip current was found to pulse at very low frequencies (VLF) and this contributed significantly to offshore sediment transport, accounting for 48% of total oscillatory flux (not considering direction). Infra-gravity (IG) frequency oscillations had a marginal contribution to offshore sediment transport within the rip (10% of total oscillatory flux) and incident wave transport was onshore (42% of total oscillatory flux). The relative influence of the wave component increased as tidal elevations increased and the rip current became inactive. For comparison, at mid-tide (h = 3.5 m) the total suspended sediment flux was in the offshore direction and four times less than during low tide. The mean flux accounted for 34% of the total transport at mid-tide. At high tide (h = 6.1 m) the total sediment transport was in the onshore direction due to the incident waves, with a 0% contribution from the mean flux.
Turner, I.L., Rau, G.C., Andersen, M.S., Austin, M.J, Puleo, J. and Masselink, G. 2013. Coastal sand barrier hydrology – observations from the BARDEX II prototype-scale laboratory experiment
The dynamics of groundwater at the land-ocean boundary has important implications to the exchange of water, nutrients and pollutants between the ocean and coastal aquifers, and varying groundwater levels may induce differing morphological response (erosion versus accretion) at the beachface. As a component of the Barrier Dynamics Experiment BARDEX II (Hydrolab IV) completed during June–July 2012 in the Delta Flume (The Netherlands), an extensive test program was undertaken to acquire a comprehensive data set of groundwater levels, pressure fluctuations, flow paths and tracer dispersion beneath the beachface and across the width of a prototype-scale sand barrier (D50 = 0.42mm). A particular feature of the experiment was the inclusion of a landward ‘lagoon' and pump system that enabled the water levels on both the seaward and landward side of the barrier to be independently varied. The completion of these experiments complimented the previous BARDEX test program undertaken in the same test facility in 2008, where a gravel barrier (D50 = 10mm) was subjected to similar wave and lagoon-sea water-level conditions. An overview of the barrier hydrology instrumentation deployed and data obtained is provided here.
Appeaning Addo, K., 2013. Assessing Coastal Vulnerability Index to Climate Change: the Case of Accra – Ghana
Coastal zones are under severe threat from climate change and its associated sea-level rise. Areas with relatively low elevations will experience either temporal or permanent flooding, while other areas will experience increased coastal erosion. Several factors within the coastal environment combine to drive coastal erosion. Identifying these variables and quantifying their risk levels enable the vulnerability index of a particular location to be estimated. This study divided the coast of Accra into three sections based on the geomorphology. The vulnerability index was estimated for the three sections by determining their relative risk factors. The ‘square root of product mean' (CVI5) method was adopted for this study. The results indicate that the coastal vulnerability index for the entire coast of Accra is 7.7, which falls within the moderate risk category. The western section is more vulnerable to sea-level rise followed by the eastern and the central sections. Inundation in the western section will result in displacement of the local population, destroy their source of livelihood and flood the Densu wetlands – a RAMSAR site.
Cho, H.Y., Oh, J.H., Kim, K.O. and Shim, J.S., 2013. Outlier detection and missing data filling methods for coastal water temperature data,
Outlier detection and missing data filling (imputation) processes are essential first step in the statistical analysis of coastal monitoring data. Here, we suggest methods for completing these key processes. An outlier detection method that uses approximate and detailed components is suggested. The decomposition of the time-series data is performed by harmonic analysis. Next, the modified z-score method is applied to the residuals (detailed component) to detect outliers. After removing the outliers in the residuals, the filling process for the missing and removed outlier data is conducted by summing the random and the approximate components. Among the environmental monitoring data, this method is applied to the coastal water temperature data. We used hourly interval coastal water temperature data provided by the NFRDI (National Fisheries Research & Development Institute). In these datasets, the dataset of the Yeong-Deok Geomuyeok (36.58 °N, 129.40 °E) station, Korea, is only used for this method application. This dataset contains some outliers and missing data. To test the model performance, this method is applied to a daily interval modeling dataset from the HYCOM (Hybrid Coordinate Ocean Model). This method provides reasonable results for outlier detection and for filling in missing data in coastal water temperature datasets.
Cooper, J.A.G., Green, A.N. and Smith, A.M. 2013. BARDEX II: Vertical stacking of multiple highstand shoreline deposits from the Cretaceous to the present: facies development and preservation.
A sequence of vertically stacked shoreline facies exposed by unprecedented water level lowering in Lake St Lucia, South Africa, records multiple occupation of the same shoreline (5–6m amsl) on at least eight occasions since the late Cretaceous. The sequence involves a basal wave-cut surface that is the outcrop of a regional unconformity cut into Late Cretaceous siltstone with occasional borings, representing a hardground (Facies 1). This is succeeded by a limestone unit indicative of sedimentation in a region of low terrigenous input quite different to today. This commences with a 10cm-thick unit comprising corals and giant clams that colonised the hardground as a shallow reef (Facies 2). The reef has an erosional upper surface that is overlain by a 30–50cm thick coquina (Facies 3) with characteristic sand-lined branching burrows, representing a coarse clastic beach unit. This is equated with the Uloa Formation of Miocene/Pliocene age. This unit has in turn been colonised by a patchy development of a coral reef of a single species, representing a renewed phase of reef development (Facies 4). The reef and the underlying Facies 3 have been waveplaned and eroded to form an erosional rocky shoreline with small potholes on a shore platform. The potholes are encrusted with barnacles and oysters to form a distinctive unit (Facies 5). The oysters and barnacles are encrusted with red algae suggesting a slight subsequent rise in sea level which is also associated with the formation of an erosional notch and a higher level shore platform with several small erosional gullies (Facies 6). These gullies are in turn encrusted by thick accumulations of serpulid worm tubes (Facies 7) into which two subsequent notches have been cut by wave action.
The shorelines preserved represent a succession of sea level highstands within a few metres of the contemporary sea level since Late Cretaceous times. They survived intervening sea level lowerings and fluvial incision by virtue of their location on an interfluve between adjacent incised valleys. Early cementation would have also been key to their preservation. Each shoreline facies was in turn influenced by the antecedent conditions imparted by the preceding shoreline as well as the contemporaneous conditions of sediment supply, sea level change and the surrounding palaeogeography. The presence of limestone and the absence of clasts or storm beach deposits suggests a protected coastline. The intermittent occurrence of coral and the reduced coral assemblage suggests that the water may not always have been fully marine.
Cordeiro Pires, A., Nolasco, R., Rocha, A. and Dubert, J., 2013. Assessing future climate change in the Iberian Upwelling System
The Western Iberian Margin is the northern limit of the Canary Upwelling System, a region of strong mesoscale activity, seasonal variability and thus very likely to be sensitive to climate change. Using a regional ocean model and data from several coupled global climate models (CGCM), climatological simulations were set up for present and for a future scenario. Forcing is obtained from averaging the outputs of an ensemble of CGCM provided by the Intergovernmental Panel for Climate Change (IPCC) A2 emission scenario. Results are focused on the continental shelf (~200 m). In general, the sea surface temperature (SST) seasonal evolution shows, for the future, an increase of about 1°C during the upwelling season (April to September) and 2°C in the rest of the year, while sea surface salinity (SSS) shows a freshening of about −0.2. These results agree with a general increase in air temperature and in fresh water input resulting from ice melting in the North Pole, which characterize this future scenario. However, differences depend on latitude and distance from the coast (higher differences to the south and more offshore, respectively). Also, SSS undergoes a shift of its minimum from July to May or September. Cross-shore sections show that SST and SSS differences are mainly observed in the upper 200 m. In winter, the typical upper slope poleward flow undergoes a slight weakening and shallowing. In summer, while the upwelling jet intensifies at the surface, it is also more restricted in both width and depth.
Dangendorf, S., Wahl, T., Mudersbach, C. and Jensen, J., 2013. The Seasonal Mean Sea Level Cycle in the Southeastern North Sea
The seasonal cycle is a prominent feature in Mean Sea Level (MSL) time series with considerable influences on flood risk in coastal areas. When analyzing MSL it is often assumed that the seasonal cycle is a stationary process, independent from inter-annual variations, but there is no obvious reason for such an assumption. In this paper the seasonal cycle of MSL at 13 tide gauges in the German Bight is investigated for its average character as well as its time dependence over the past 166 years. A seasonal trend decomposition method is used to analyze the inter-annual fluctuations in amplitudes and phases of the seasonal cycle. In the German Bight the seasonal cycle accounts for up to 44 % of the observed monthly MSL variability. The mean seasonal cycle peaks during November at all stations. The mean amplitude varies between 14 and 20 cm and increases from the south-western to the north-eastern stations. Throughout the last 166 years it is found that the amplitudes as well as the phases of the seasonal cycle are marked by a considerable inter-annual variability. While most records, all starting in the 1930's or later, do not exhibit a significant trend the longest record at Cuxhaven displays a significant long-term trend of 0.2 ± 0.1 mm/yr. This trend is mainly caused by large values at the end of the 1970's and the beginning 1980's. Simultaneously, the annual peaks shift from the late autumn to winter months (December to February). These changes are caused by extraordinary large trends during the months from January to March, exceeding those in the remaining months by up to 4 mm/yr. These changes are in phase with an intensification of large-scale atmospheric circulation patterns over the North Atlantic bringing more frequent westerly winds over the North Sea.
Dreier, N., Schlamkow, C., Fröhle, P. and Salecker, D., 2013. Changes of 21st Century's average and extreme wave conditions at the German Baltic Sea Coast due to global climate change.
On the basis of hourly simulated wind data from a regional circulation model (Cosmo-CLM) long-term time series (1960–2100) of wave parameters were compiled for two of the SRES scenarios A1B, B1 at three locations along the German Baltic Sea Coast. The time series of wave parameters were calculated with the help of statistical correlations between observed wind and wave data, which were derived for the three locations in the study area. Furthermore, we applied a wave model for the Western Baltic Sea to correct some of the calculated wave information. The key findings of this study are that: (i) significant changes of average wind conditions can directly be linked to significant changes of the average wave conditions, (ii) a spatial pattern for the changes of average wave conditions can be found, (iii) no general trend can be found for the changes of extreme wave conditions. Comparisons of wind conditions, as simulated by the regional circulation model, for the past and the future are showing two main changes: (a) increases of average wind velocities to the end of the 21st century up to 4% and (b) more wind events from westerly and less events from easterly directions. The changes of the average wind velocities are resulting in increases of the average significant wave heights at westerly wind exposed locations up to 7% and small decreases of the average significant wave heights at easterly wind exposed locations. The future changes of the wave directions, with more wave events from W-NW and fewer events from N-NE, can be connected to the future changes of wind directions. Analyses of extreme wave heights with a return period of 200 years are showing both increasing and decreasing changes of up/down to /−14%. At one location of the study area (Warnemünde) a slight increasing trend for the change of extreme wave heights to the end of the 21st century exists.
Eom, H.-M., Kang, K., Ryoo. S.B., Lee, Y.H., 2013. Development of Coastal Inundation FOrecasting System (CIFOS) and Its Application to the Future Climate Change
The low-lying area is frequently damaged by the typhoon, monsoon and high tide resulting inundation. Especially, the southern coastal area in Korea was seriously damaged by the typhoon-induced heavy flood in 2003, which took tremendous toll on human lives and properties. The National Institute of Meteorological Research (NIMR) has been developing and improving the Coastal Inundation Forecasting System (CIFOS) for the provision of flooding information and the effects of the climate change on coastal areas. The system was applied to typhoon Maemi (0314) case to simulate flooding process and inundation area in the south coast of Korea. We also tried to estimate the change of coastal environment by the future climate conditions: three cases of sea level rise 0.4, 0.8, and 1.0 m. The model results during typhoon Maemi(0314) period showed good agreement with field observations. According to the predicted coastal environment in Masan port area, the inundation area was increased by 168 %, 335 % and 393 % for 0.4 m, 0.8 m and 1.0 m sea level rise cases, respectively.
Figueiredo, S.A., 2013. Modeling climate change effects in southern Brazil.
Along the coast of Rio Grande do Sul state, southern Brazil, differences on coastal configuration are generally accompanied by changes in substrate slope, where steeper gradients characterize coastal projections and gentle gradients the coastal embayments. This study focus on coastal response to climate change effects at two sectors along RS coast: Cassino embayment and Conceição lighthouse projection. The former has been under very high rates of progradation, on the order of at least 3 m/yr at geological and historical time scales. Whereas Conceição region has been undergoing rates of recession reaching −3.6 m/yr. In order to forecast coastal response to the effects of climate change at these sites over several time horizons (2030–2070–2100), model simulations using the DRanSTM (Dilating Random Shoreface Translation Model) were performed. Simulation results have demonstrated that Cassino sector is particularly vulnerable to such effects, and therefore presents extremely high recession distances (102–103 m). Despite the historical erosion trend at Conceição lighthouse region it presented lower recession rates in comparison to Cassino sector. Hence a possible inversion on shoreline historical trends can be expected for the future. These results are in line with the expectations, that sectors characterized by low gradient shoreface profiles are at very high risk of future shoreline erosion. The high degree of vulnerability in Rio Grande do Sul coast is further highlighted when compared to other embayments around the world, such as those at SE Australia, which when subjected to similar rates of sea level rise (max. 1.1 m) presented recession distances that were orders of magnitude lower (10–102). The results presented here express the urgent need for the development and implementation of coastal management and adaptation plans to climate change that account for site specific characteristics.
Jose M. Horrillo-Caraballo, Dominic E. Reeve, Dave Simmonds, Shunqi Pan, Andrew Fox, Richard Thompson, Simon Hoggart, Samuel S.H. Kwan, Deborah Greaves
Horrillo-Caraballo, J.M., Reeve, D.E., Simmonds, D., Pan, S., Fox, A., Thompson, R., Hoggarth, S., Kwan, S.S.H. and Greaves, D., 2013. Application of a source-pathway-receptor-consequence (S-P-R-C) methodology to the Teign Estuary, UK.
Coastal areas are economically vital in terms of population, industry, trade and tourism. The numbers of people and properties at risk will increase as economies grow or develop, while climate change will amplify the likelihood of extreme events, as well as accelerate potential habitat decline. The development of a systematic approach to deliver both a low-risk coast for human use and healthy habitats subject to multiple change factors is envisaged within the European project THESEUS of which this study forms a part. Plymouth Sound to Exe Estuary (UK) is one of several project sites. This site involves complex coastal and estuarine processes; interactions between coastal defence structures, coastal morphology and ecological habitats; and significant economic, social and environmental impacts, which makes a really interesting and challenging site to study. The source-pathway-receptor-consequence or ‘S-P-R-C' methodology was adopted to identify the risk of flooding and erosion. This method is a simple conceptual model for representing systems and processes that lead to a particular consequence. Sources, pathways and receptors have been identified and defined in a GIS system, the information for the sources was derived from tide gauges at Plymouth and Exmouth, simulated surge and wave conditions derived from running POLCOMS (over 4 × 30 year time slices) for present conditions and the A1B scenario (short-, mid- and long-term). Pathway information was obtained from a variety of sources but largely from the UK Environment Agency databases. Receptors were defined on the basis of land use obtained from the CORINE database from the European Environment Agency, terrain elevation data and defence type. It is concluded that should the extreme changes for the four main sources (mean sea-level, waves surge and river flow) coincide, the impact would be catastrophic if land usage remains as it is today.
Kong, J., Shen, C.J., Ye, R.H., 2013. Analytical research on the tidally-induced groundwater wave propagation mechanism in coastal aquifers.
With increasingly more attention paid to coastal environment, research on the interaction between subsurface and surface water has become a hot subject. Being different from surface water, tidally-induced groundwater moves slower with special over-height far away from the coastal line, which is higher than the mean sea level. Such a special hydrodynamic characteristic hints the special propagation mechanism is different from traditional surface wave. In order to reveal the tidally-induced groundwater wave propagation mechanism and analyze the influence of latent coastal beach profile variation because of mean sea level rise, theoretical research is focused on a newly derived high-order analytical solution corresponding to non-linear Boussinesq equation applied on sloping beach. Research indicates that: Firstly, the tidal induced groundwater wave energy mainly concentrates on the former three order constituent waves. The variation of beach profile because of sea level rise will not change the proportion relationship among the constituent waves; Secondly, the over-height's increase is influenced by the conductivity decrease, porosity enlargement or tidal amplitude widening; Thirdly, mild beach slope and large conductivity are favorable for wave propagating with longer wavelength. In the end, the rise of mean sea level increases the aquifer thickness and then leads to the faster propagation speed of groundwater wave, lower over-height and makes the interaction between surface and subsurface water more intensively reflected in farther tidal wave signal landwards.
Mendes, R., Vaz, N., Dias, J.M., 2013. Potential impacts of the mean sea level rise on the hydrodynamics of the Douro river estuary
Numerous studies based on tide gauge records demonstrated the sea level rise on the Portuguese coast during the last century. Different climatic models predict a mean sea level rise for this coast ranging between 0.28 m and 0.42 m, for the period 2091–2100 relative to 1980–1999. Thus, the potential evaluation of the sea level rise impact on the Portuguese coast becomes critical, especially in sensitive areas as estuaries. The main aim of this work is to evaluate hydrodynamic changes in the Douro estuary induced by the sea level rise. A baroclinic finite volume numerical model was implemented to the Douro estuary in a 2D mode. The model calibration was performed comparing predicted and observed sea surface elevation time series for several stations. The tidal input at the ocean open boundary forces the 2D hydrodynamic model considering actual and future mean sea levels. At the landward boundary the model is forced with the freshwater discharge. The research explores changes in current velocity and amplitude and phase differences of the main diurnal and semi-diurnal tidal constituents along the estuary. The results suggest local significant changes in the Douro hydrodynamics in response to the sea level rise. Nevertheless, the differences don't affect the general estuary's circulation. Concerning the main tidal constituents, the amplitude increases and the phase decreases, revealing that the tide tends to propagate faster upstream and with higher tidal ranges. Owing to the increasing of the amplitude and the water level, the current velocity values tend to decrease in the estuary, mainly near the low-lying areas.
Rouse, H.L, Blackett, P., Hume, T.M., Bell, R.G, Britton, R. and Dahm, J., 2013. Coastal Adaptation to Climate Change: a New Zealand story.
The requirement for using a participatory approach to consider options for adapting to climate change is well documented, but there are some key challenges of engaging with communities, especially over the complexities of projected climate change impacts and possible adaptation options. Here we describe the development of a two-stage method aimed to overcome these challenges, and the testing of this method in a coastal community in Whitianga on the Coromandel Peninsula, North Island of New Zealand. First, at an Open Day we used projections of sea-level rise driven changes to coastal inundation, erosion and habitat change and mapped them on large aerial-photo maps to use as the basis for a participatory mapping exercise. The purpose of the Open Day was to elicit input on valued aspects of the Whitianga community that might be at threat from climate change. Second, at a follow-up Workshop we worked with the community to explore the potential for adaptation options to provide ‘solutions' to these issues, exploring who the winners and losers would be for each option, and what would be required to enable the options to be actioned. The maps were a key tool in this engagement case-study, and we reflect on them in our discussion of their development and usefulness. Finally we summarise the lessons learned in this case study and describe four key inputs to successful community engagement: the right team, the right data, the right support, and the right resources.
Weisner, E. and Schernewski, G. 2013. Adaptation to climate change: A combined coastal protection and re-alignment measure in a southern Baltic tourism region.
The German federal state of Mecklenburg-Vorpommern has an outer Baltic coastline of 354 km of which 70% is subject to erosion with an average retreat of 0.34 m/yr. Altogether 135 km of coastline is protected by wooden groynes, beach and dune nourishment, protective dunes and forests, dykes, seawalls and breakwaters at an annual maintenance cost of about 15.5 mio €. During the last decades the sea level rose at a rate of 1.2 mm/yr and an accelerated rate of rise is likely in future. A combined coastal protection and managed re-alignment scheme was implemented in an area of about 1000 ha, which aimed to adapt to the challenges associated with climate change, to reduce costs for coastal protection and to support environmentally sustainable development. The scheme covers 6 km of coastline comprising the seaside resort Markgrafenheide and the wetland and coastal moor Hütelmoor. We provide here the historic background to the area, document the scheme planning and implementation process, and evaluate the approach and success of the scheme. From an implementation and coastal and environmental protection perspective, the project was successful. Despite early public information and participation in planning of the scheme, a strong local opposition and a negative public perception developed which enforced modifications of the scheme.
Soomere, T., 2013. Extending the observed Baltic Sea wave climate back to the 1940s.
Systematic visual wave observations have been performed since 1946 at numerous locations on the eastern coast of the Baltic Sea. The records of wave height that mostly exist since 1954 are reconstructed back to 1946 using the high correlation (about 0.85) between the wave height and qualitative measures of sea state, and a linear regression between these quantities at Ventspils and Liepaja (Kurzeme Peninsula, Latvia). The analysis confirms the well-known properties of the Baltic Sea wave fields such as a relatively low overall wave intensity, short wave periods at the nearshore, high spatio-temporal variations in the average wave height and a strong evidence of decadal-scale changes. A part of the relevant changes are in counterphase for the southern and the northern Baltic Sea. There has been a relatively rapid decrease in the average wave height in the eastern Baltic Sea from the end of 1940s until ~1970, and a slow increase since then. No secular trend in the wave intensity is evident at any observation site from the Curonian Peninsula up to the northern Baltic Proper. The results suggest that much longer wave hindcasts (at least 50–60 years) driven by realistic wind patterns are necessary to properly quantify the changes to the wave fields in this basin.
Udo, K., Takeda, Y., Yoshida, J., Mano, A., 2013. Long-term area change of two tidal flats in Japan and its future projection due to sea level rise
This study investigates century-scale area changes of two tidal flats in Japan facing the Ariake Sea and the Yatsushiro Sea, and Tokyo Bay, and their future projections in order to estimate the effect of sea level rise due to climate change on the tidal flats. The long term area change shows notable erosion of tidal flats due to the large scale of landfill reclamation in cities for coastal development and sea reclamation in localities for farmland development, during the period of Japan's rapid growth after 1950s. The future projections using the recent sea bed topography and estimation result of sea level rise show that there is much difference between the future projections with and without consideration of vertical accretion rate. It is estimated that tidal flat erosion up to tens of square kilometers may occur in a long term even only in the study areas. Possibility of serious damage of tidal flats was indicated, though more precise estimation considering other effects such as flood characteristic change due to the climate change is needed in the future.
Valentim, J.M., Vaz, L., Vaz, N., Silva, H., Duarte, B., Caçador, I. and Dias, J.M., 2013. Sea level rise impact in residual circulation in Tagus estuary and Ria de Aveiro lagoon.
Nowadays, there is a special concern about the possible impact of sea level rise in hydrodynamic patterns of coastal systems and its consequence in contingent ecosystems. In the present work, the effects of sea level rise in residual circulation are analyzed in two of the most important Portuguese coastal systems, Ria de Aveiro lagoon and Tagus estuary. The role of rivers inflow on residual circulation is also analyzed under different sea level scenarios. Several projections of river discharges were considered and two scenarios for sea level were adopted: actual and locally predicted sea level rise. The methodology followed comprises the exploitation of previously validated 2D hydrodynamic numerical models (MOHID) developed for both systems. Results indicate that rivers discharge effect cannot be unconsidered in the long term hydrodynamic analysis for both systems, once residual currents intensity could be at least 40% and even 100% higher in maximum inflow than in typical inflow and no discharges scenarios, respectively. In Tagus estuary, the upper bay is the most affected area in a sea level rise scenario, namely in the upper zone (with extensive intertidal areas) where differences in the residual currents intensity can be higher than 100%. In Ria de Aveiro lagoon, differences between actual and sea level rise could be higher than 80%. Narrow and shallow channels are the most affected areas, revealing the significant impact of sea level rise in the intertidal zones. Consequently, the predicted changes in these systems hydrodynamics could influence the long term transport and their actual equilibrium and, as such, affect the natural state of the contingent biological communities.
Wahl, T., Haigh, I.D., Dangendorf, S., and Jensen, J., 2013. Inter-annual and long-term mean sea level changes along the North Sea coastline.
Globally, mean sea levels are rising and there is concern that the rate of rise will accelerate throughout the 21st century significantly impacting growing coastal communities. Currently, most coastal management assessments are based on global mean sea level projections from the Intergovernmental Panel on Climate Change's Fourth Assessment Report. However, temporal and spatial variability of mean sea level change needs to be identified in order to establish an accurate projection of coastal management needs due to erosion and flooding associated with global sea level rise. This paper assesses historic changes in mean sea level from the beginning of the 19th century to present using 30 long and high quality tide gauge records located around the coastline of the North Sea. The North Sea coast is one of the most densely populated coastlines in the world. It contains a significant proportion of Europe's coastal flood risk as exemplified by London, Amsterdam and Hamburg, and the other extensive lowlands, and has a long history of significant coastal flooding. Previous analyses of mean sea level changes along Europe's coastlines have tended to be conducted at a national level, using a variety of different methods and sea level records of different quality and length. This study has three main objectives: (1) to examine the inter-annual variations observed in mean sea level across the North Sea region; (2) to examine linear and non-linear longer-term trends in relative and absolute mean sea level from the beginning of the 19th century to present; and (3) to assess whether 19 years of altimetry data provide valuable information on the spatial patterns of sea level trends and inter-annual variability in the North Sea.
Cordeiro Pires, A., Nolasco, R. and Dubert, J., 2013. On the origin of summer upwelled waters in Western Iberian Peninsula
As in most eastern boundary systems, on the Western Iberian Margin there is coastal upwelling during summer due to the alongshore northerly winds and the consequent offshore displacement of surface waters. This work addresses the origin of these upwelled waters. Using a regional ocean model, a climatological configuration and a lagrangian particle module that is run backward in time, we trace the trajectory of particles arriving at four coastal areas, delimited by the 200-m isobath, approximately, and at three depths: 20 m, 40 m and 60 m. Each point is traced backward for one month, with arrival dates of June 30, July 30 and August 30, the typical upwelling months. We find out where the particles were on June 1, July 1 and August 1, respectively, how deep they have reached and what distance they have traveled. In general, the points of origin were shallower (in the upper 100 m) for the particles that traveled the greatest distances (up to 500 km). These particles come mostly from the north and trace alongshore pathways at 20–40 km from the coast, i.e., within isobaths 100–200 m, the preferential path of the upwelling-associated equatorward jet. Conversely, particles that originate from deeper levels, down to 600 m, come from shorter distances, approximately 100 km. Some particles originate to the west of their point of upwelling, giving evidence of being dependent on meandering and other mesoscale features, such as offshore eddies and upwelling filaments.
Cravo, A., Cardeira, S., Pereira, C., Rosa, M., Madureira, M., Rita, F., Luís, J. and Jacob, J., 2013. Nutrients and particulate matter exchanges through the Ria Formosa coastal lagoon.
The Ria Formosa lagoon (south coast of Portugal) is a highly productive shallow mesotidal system of high water renewal through six permanent connections to the ocean. The three inlets in the western sector represent ~ 90% of the total tidal prism. To understand spatial and temporal dynamics of nutrients, chlorophyll a (proxy of phytoplankton) and particulate matter, data acquisition of these parameters along with current velocity was conducted hourly during two consecutive semi-diurnal spring and neap tidal cycles (~12.5 h) in the three inlets of Ria Formosa western sector, in late autumn of 2011. In all three inlets, nutrients ranges were typical for this time of the year, varying in antiphase relative to tidal signal, although less evident during the neap tide. Chlorophyll a and suspended solids concentrations were lower during the neap tidal cycle with less evident tidal variation than for nutrients. Net transport results show that Ria Formosa plays an important role in the mass export of nutrients to the adjacent coastal area, particularly during spring tides, with a greater contribution by the Faro-Olhão inlet, followed by the Armona and Ancão inlets. These two, regardless of the residual tidal prism, export nutrients while suspended solids were imported. The Faro-Olhão inlet presented different behaviour: it acts as a flood dominated inlet importing chlorophyll a and nitrate, and exporting ammonium and suspended solids. Nonetheless, values can change due to tidal variability, asymmetry and distortion, and interconnection of inlets inside the lagoon. To further understand the seasonal variation of this system more surveys will be conducted.
Franklin, G.L., Mariño-Tapia, I. and Torres-Freyermuth, A., 2013. Effects of reef roughness on wave setup and surf zone currents.
Circulation in reef systems controls an important number of key processes, such as the transport and dispersion of larvae, nutrients, and sediments. In fringing reef systems, where a shallow lagoon backs onto the reef crest, circulation appears to be dominated by wave breaking. Despite the identified importance of wave driven flows within reef systems, there is a lack of detailed knowledge on these processes within the surf zone of reef crests and the effects reef roughness has on these flows. A numerical study, using two-dimensional (2DV) simulations, was carried out in order to improve the understanding of wave-driven flows in the surf zone of a fringing reef. The model used is Cornell Breaking Wave and Structures (COBRAS), which solves the Reynolds-Averaged Navier-Stokes (RANS) equations with a turbulence closure scheme. The effect of different reef roughness on wave height, wave setup, infragravity waves and mean flows was studied. Model results revealed that wave setup increases significantly (~22%) with increasing bed roughness, consistent with prior studies on sandy beaches. Furthermore, cross-shore velocity structure is heavily affected by bed roughness. The latter implies that the coral reef flattening trend observed world-wide could result in a decrease in the circulation within the lagoon with important implications for reef health.
Jacob, J., Cardeira, S., Rodrigues, M., Bruneau, N., Azevedo, A., Fortunato, A.B., Rosa, M. and Cravo, A., 2013. Experimental and numerical study of the hydrodynamics of the western sector of Ria Formosa.
The western sector of Ria Formosa, a lagoon system in the south of Portugal, represents approximately 90% of the total tidal prism of the lagoon and includes three inlets. Two sets of field campaigns to characterize the hydrodynamics of this sector in neap and spring tide conditions were conducted in the autumn of 2011 and spring 2012. The main findings related to the inlets hydrodynamics and water exchanges between the lagoon and the ocean along semi-diurnal tidal cycles are presented. To estimate the relative contribution of the three inlets to the water exchanges between Ria Formosa and the ocean, discharges were evaluated hourly along complete neap and spring semi-diurnal tidal cycles and the tidal prisms computed. In addition, two sea level time series measured in Faro-Olhão inlet and Faro commercial pier were harmonically analyzed. The results were compared with previous studies and used to validate the ELCIRC hydrodynamic model. This model provided additional information about the circulation and tidal prisms and distortion inside the western Ria Formosa. This study confirmed the Faro-Olhão inlet as the main inlet in terms of contribution for the total tidal prism. It is shown that the Ancão inlet lost hydraulic efficiency, contributing less than 6% to the total tidal prism in all situations and the Armona inlet gained efficiency in spring tide and lost efficiency in neap tide. Moreover, the Faro-Olhão inlet exhibits flood prisms higher than ebb prisms under neap and spring tides, suggesting a residual circulation towards the Ancão and Armona inlets.
Lee, M.E., Kim, G. and Nguyen, V.T., 2013. Effect of local refinement of unstructured grid on the tidal modeling in the south-western coast of Korea.
To deal with a very complicated bathymetry in the south-western coast of Korea (SWCK), in this paper a numerical calculation with respect to varying grid and bathymetric resolutions was carried out for M2 barotropic tidal motion using FVCOM. In order to improve the model accuracy, horizontal grid resolutions resolving irregular coastlines and bathymetry together with data accuracy are considered. To do this, three refined horizontal grid resolutions were constructed in the nested local area around SWCK. At each horizontal grid structure, two different bathymetry resolutions were applied; the higher resolution based on a latest survey (2007) is more accurate. Bathymetric data with higher resolution was reconstructed as two different samples of data, to test the effect of resolving basic bathymetric data and the improvement of data accuracy, separately. From the test results, it was found that the accuracy of modeled M2 tidal elevation in this region can be improved dominantly by increasing the accuracy of basic bathymetric data, instead of resolving coastline and islands or increasing the resolution of bathymetry.
Lencart e Silva, J. D., Azevedo, A., Lillebø, A.I., Dias, J.M, 2013. Turbidity and seagrass meadows under changing physical forcing.
Seagrass meadows support a range of ecosystem functions in coastal lagoons, from habitat and shelter of invertebrates and fishes to stabilizing sediments, serving at the same time as important ecological quality status indicators due to their sensitivity to water quality parameters. Seagrass meadows are recognized as one of the most productive ecosystems on Earth. Those in mesotidal mid-latitude lagoons with low flushing times primary production are greatly affected by turbidity. Here, we investigate the physical controls of turbidity in Ria de Aveiro, Portugal, by simulating its response to varying conditions of tidal and river forcing. A 2-dimensional hydrodynamic and transport model developed and calibrated for this coastal lagoon was forced with tide at the inlet, wind and river inflow. The tidal flow was found to be the main driver of changes in turbidity with river-borne plumes assuming some relevance during extreme events. The turbidity response for scenarios of increasing storm-driven events and mean sea level was compared between two existent seagrass patches and the differences in the turbidity conditions put in context of their relevant physical mechanisms. A difference in response was shown to exist between the two patches, mainly attributable to the tide which resuspends the spatially-varying sediments deposited seasonally by river inflow.
Lippmann, T. C., J. Irish, and Hunt, J., 2013. Observations of the vertical structure of tidal currents in two inlets.
Observations of the vertical structure of broad band tidal currents were obtained at two energetic inlets. Each experiment took place over a 4 week period, the first at Hampton Inlet in southeastern New Hampshire, USA, in the Fall of 2011, and the second at New River Inlet in southern North Carolina, USA, in the spring of 2012. The temporal variation and vertical structure of the currents were observed at each site with 600 kHz and 1200 kHz RDI Acoustic Doppler Current Profilers (ADCP) deployed on low-profile bottom tripods in 7.5 and 12.5 m water depths near the entrance to Hampton Inlet, and in 8 and 9 m water depth within and outside New River Inlet, respectively. In addition, a Nortek Aquapro ADCP was mounted on a jetted pipe in about 2.5 m water depth on the flank of the each inlet channel. Flows within the Hampton/Seabrook Inlet were dominated by semi-diurnal tides ranging 2.5 - 4 m in elevation, with velocities exceeding 2.5 m/s. Flows within New River inlet were also semi-diurnal with tides ranging about 1 – 1.5 m in elevation and with velocities exceeding 1.5 m/s. Vertical variation in the flow structure at the dominant tidal frequency are examined as a function of location within and near the inlet. Outside the inlet, velocities vary strongly over the vertical, with a nearly linear decay from the surface to near the bottom. The coherence between the upper most velocity bin and the successively vertically separated bins drops off quickly with depth, with as much as 50% coherence decay over the water column. The phase relative to the uppermost velocity bin shifts over depth, with as much as 40 deg phase lag over the vertical, with bottom velocities leading the surface. Offshore, rotary coefficients indicate a stable ellipse orientation with rotational directions consistent over the vertical. At Hampton, the shallower ADCP, but still outside the inlet, shows a rotational structure that changes sign in the vertical indicating a sense of rotation at the bottom that is opposite to that at the surface. Within the inlet, the flow is more aligned with the channel, the decay in amplitude over the vertical is diminished, the coherence and phase structure is nearly uniform, and the rotary coefficients indicate no sense of rotation in the flow. The observations are qualitatively consistent with behavior described by Prandle (1982) for shallow water tidal flows.
Nikolkina, I., Soomere, T., Didenkulova, I., 2013. Wave climate in Peipsi Lake.
The main features of wave properties in relatively large but shallow Lake Peipsi (Estonia/Russia) are determined based on wave measurements at its western coast (58.75°N 27.1°E) in summer and autumn 2005–2007. Although the data set is relatively limited, it still covers 263 days and characterizes well the basic properties of wave climate in this water body. The wave regime is mostly calm, with the long-term average significant wave height below 0.3 m and seas with Hs < 1.2 m covering at least 2/3 of the ice-free time. The seasonal variation in wave properties mimics the analogous variation in the wind speed, with the most stormy months October–December. Wave heights are, on average, considerably lower in summer (July–August) than in autumn (October–November). Significant wave heights >1 m were recorded in autumn and covered 3% or the measurement time. The maximum recorded wave height Hs = 1.98 m occurred on October 27, 2005. The mean periods are mostly concentrated in a range of 1.5–2.5 s and exhibit an almost Gaussian distribution.
Park, Y.-G., Yeh, S.-W., Hwang, J. and Kim, T., 2013, East China Sea circulation from a high resolution ocean circulation model.
Using the results from a high-resolution global ocean circulation model, the present study describes the circulation over the East China Sea and the origin of the Tsushima Warm Current. We focus on the interaction between the Taiwan Warm Current, the Tsushima Warm Current, and the Kuroshio intrusion north of Taiwan and east of Kyushu by comparing mass fluxes. Although the modeled transport of the Tsushima Warm Current is weaker than observed values by about 30 %, that of the Taiwan Warm Current is within the known range. The transport of the latter is large enough to supply the former. Thus, in this model, the net intrusion of the Kuroshio towards the shelf between Taiwan and Kyushu would not make a significant contribution to the Tsushima Warm Current. Conversely, the flows northeast of Taiwan and west of Kyushu show a strong presence of branch currents toward the inner shelf from the Kuroshio. To resolve this apparent contradiction, we estimated mass budgets for the areas around Taiwan and west of Kyushu. The Taiwan–Tsushima Current System and the Kuroshio are located very closely to each other along the shelf break, and if they are not differentiated properly using high-resolution data, one could overestimate the strength of the branch currents or the onshore intrusion of the Kuroshio. Considering the similarity between the apparent branch currents from this model and the previously reported results, the branch currents, especially west of Kyushu, may not be as strong as previously suggested.
Picado, A., Alvarez, I., Vaz, N., and Dias, J.M., 2013. Chlorophyll concentration along the northwestern coast of the Iberian Peninsula vs. atmosphere-ocean-land conditions.
The aim of this work is to investigate the relationship between the atmosphere-ocean-land conditions and chlorophyll a (Chl-a) formation along the northwestern coast of the Iberian Peninsula. Spatial and temporal distribution of Chl-a concentration, sea surface temperature, surface winds and rivers discharge were analyzed from 1998 to 2007, using remote sensing data. Generally, the Chl-a concentrations are higher near the coast showing a seasonal variability. In fact, along the coast there are higher Chl-a concentrations during the dry season (April to September) which can be associated to the upwelling favorable conditions (southward winds). These favorable conditions are related to the presence of cold nutrient-rich water which upwells towards the surface layers enhancing the primary production. During winter months, the wind pattern is usually upwelling unfavorable (northward winds); however high Chl-a concentration also occurs near the coast. These high values could be related to the inland nutrients input through rivers discharge and winter upwelling events. Afterwards, correlation coefficients were computed between Chl-a and upwelling index, SST and rivers discharges. Between June to September chlorophyll and upwelling index are positively correlated, increasing southward (0.58 to the south of the study area). During winter, the correlation coefficient between chlorophyll and rivers discharge is 0.75 in the northern region of the study area. Therefore, during summer months the chlorophyll variations could be explained mainly by the frequent upwelling events, whereas during winter months, high chlorophyll concentration near coast depends on rivers discharges.
Sénéchal, N., Sottolichio A., Bertrand, F., Goeldner-Giannella, L., Garlan, T., 2013. Analysis of currents and storm surge in a mixed-energy tidal inlet during storm conditions.
Coastal morphodynamic processes around tidal inlets in mixed-energy environments are particularly complex due to severe tide and wave conditions. Collecting data in this area is generally very challenging. Here we present the first hydrodynamic data collected in the outer inlet of the Arcachon lagoon, a mixed-energy inlet situated on the southern part of the French Atlantic coast. Data consist in vertical current profiles and sea surface elevations collected on the offshore edge of the ebb delta under various tidal and wave conditions. In particular data were collected during the severe Joachim storm associated to wave heights up to 8 m. Preliminary results indicate that current profiles, intensities and direction are very sensitive to wave conditions. Under energetic conditions, the vertical profile of currents become uniform and the longshore drift is enhanced (up to 1.5 m/s). Nevertheless data show that under severe wave conditions (Hm0 > 6.0m) and despite high incidence of waves, the longshore drift is weaker (l< 1 m/s) than under ‘usual' storm conditions associated to Hm0 = 4 – 5m. More surprisingly, directions of the longshore drift are not always consistent with wave incidence under those severe storm conditions and the cross-shore components are very weak while under less energetic conditions we observe intense offshore currents (up to 0.8 m/s).
Sousa, M.C., Vaz, N., Alvarez, I. and Dias, J.M., 2013. Effect of Minho estuarine plume on Rias Baixas: numerical modeling approach.
The Minho River, situated 30 km south from the Rias Baixas, is the most important freshwater source flowing into the Western Galician coast. This discharge is particularly important in driving the circulation and hydrography of this coastal region. To study this important issue, numerical modeling may constitute an important tool being used to understand the coastal plume effects under different conditions. The main purpose of this study is to implement and validate a marine model able to reproduce the propagation of the Minho estuarine plume. The chosen period for the validation was the spring of 1998, because a high Minho River discharge was reported as well as favorable wind patterns to spread the river plume towards the Rias Baixas. The numerical model MOHID was used through a downscaling approach with a three-level one-way nested scheme. The numerical predictions show good agreement with the observed water level in the entire domain. Also, the measured components of the velocity are well represented by the model, as well as the observed pycnocline, which is predicted for the observed depth. According to the model results, a buoyancy intrusion caused by the Minho river reverses the normal estuarine salinity longitudinal gradient of the Rias de Vigo and Pontevedra. Otherwise, this pattern is not observed in the Ria de Arousa. All these patterns are corroborated by in situ measurements. In summary, the validation results show that the model adequately reproduces the hydrodynamic and thermohaline patterns of the Western Galician coast.
Suursaar, Ü. and Kullas, T., 2013. Hindcast of wind-driven circulation in a system of straits between the Baltic subbasins in 1966–2011.
The paper presents a study of currents and sea level variations in the nearly tideless sub-basins of the Baltic Sea, the Gulf of Riga and the West Estonian Archipelago Sea, using a high-resolution (of order 1 km grid) shallow sea hydrodynamic model. The model was forced by the measured wind and sea level data obtained from the data-base of the Estonian Meteorological and Hydrological Institute over the period 1966–2011 and validated using the measurements of currents obtained with a bottom-mounted RDCP in the Northern Gulf of Riga in summer 2011 and by sea level measurements at the Pärnu tide gauge in 2011. Flows within the two sub-basins and in the five straits were wind-dependent, each location having its specific wind directions for switching between the patterns. All the straits take part in the water exchange, functioning together as an interconnected oscillatory system and provoking movements in the hydrochemical front between the water masses of different properties. Owing to the factual seasonality in the wind conditions, northward flows prevailed in the centrally located Suur Strait in autumn and winter, but southward flows in summer. Annual net (northward) outflows prevailed in the straits of Suur, Hari and Voosi, but inflows in the Irbe and Soela Straits. The reconstructed long-term variations in water exchange over 46 years indicated climatologically induced interannual variations which are probably related to changes in atmospheric circulation above Northern Europe.
Teixeira, C. E.P. and Machado, G. T., 2013. On the temporal variability of the Sea Surface Temperature on the Tropical Southwest Atlantic Continental Shelf
In this study, we used 29 years of daily 4-km AVHRR Pathfinder Version 5.2 (PFV5.2) data to study the SST temporal variability over the continental shelf in the Southwestern Tropical Atlantic Ocean (SWTA) (1 to 6° S and 41 to 35 W). Firstly, we evaluated the cloud cover and assessed the annual and semi-annual deterministic signals using a harmonic analysis. The annual plus the semi-annual cycles were removed from the original data and a low-pass filter was used to estimate the contribution of the inter-annual component. Finally, the inter-annual signal was also removed and the variance associated to the remaining residuals was calculated to address the intra-annual component. We show that the region is covered by clouds – and SST data unavailable - between 40% and 60% of the time. The annual signal explains most of the variability over the area with a coefficient of determination higher than 70% and amplitudes ranging from 1° to 1.5°C. The amplitudes increase eastwards and towards the coast. The phase of the annual cycle presents values between 40 and 60 days with respect to the 1st of January, occurring earlier over the eastern continental shelf. The semi-annual signals present amplitudes close 0.5 °C in most of the region decreasing towards offshore regions. The continental shelf as whole, experienced weak inter-annual variability with variance values around 0.2 °C. After the annual and semi-annual signals were removed, the inter-annual signal explains 30–45 % of the residual. The intra-annual variability presents variance values between 0.2 and 0.3°C and explains most of the residual variability. Both inter and intra-annual SST variability in the SWTA is spatially homogenous. For the first time, the SST temporal variability ranging from sub-seasonal to inter-annual was addressed in the SWTA continental shelf region. In light of the results, we have showed that the SST in the Tropical Southwest Atlantic continental shelf presents a small temporal and spatial variability. Most of the SST is explained by the annual cycle followed by the intra-annual variations.
Viikmäe, B., Torsvik, T., 2013. Quantification and characterization of mesoscale eddies with different automatic identification algorithms
Automatic methods for detection of mesoscale eddies are usually based on either physical (e.g. Okubo-Weiss parameter) or geometrical (e,g, streamline winding-angle) flow characteristics. In this paper, a hybrid method combining the strengths of the two different approaches is applied to the Eulerian velocity fields for two case studies: (i) the Gulf of Finland (the Baltic Sea) and (ii) the Raunefjord and Vatlestraumen area south-west of Bergen, Norway. Velocity fields are investigated with a hybrid winding-angle method (HWA), where the Okubo-Weiss parameter is first used to detect potential eddies, and the winding-angle method is used locally within these regions to test the Okubo-Weiss result. In the Gulf of Finland, the HWA method results in a substantially reduced number of detected eddies compared with the Okubo-Weiss result, indicating that the Okubo-Weiss parameter severely overestimates the number of eddies. In Vatlestraumen, there was a better correspondence between results obtained by the HWA and the Okubo-Weiss methods. The HWA method requires careful analysis since more than one streamline may identify the same eddy structure.
Ab Razak, M.S., Dastgheib, A., Roelvink, D. 2013. Sand bypassing and shoreline evolution near coastal structure comparing analytical solution and XBeach numerical modelling
The present study is aimed at comparing the numerical and analytical estimation of the shoreline near an idealized groyne structure. Moreover, the impact of sand bypassing on the accretion at the updrift coast calculated by analytical Pelnard solution is compared against the XBeach numerical model. The application of the XBeach model shows some promising results. Prior to bypassing, the resulting shoreline pattern from numerical (XBeach) model resembled the Pelnard model with slight differences. The circulation of wave driven-currents due to diffraction is responsible for the formation of a sand wedge at the downdrift side which cause the coastline to prograde. Despite the fact that the bypassing volume simulated by XBeach is smaller than the analytical solution, the shoreline pattern seems to reasonably follow the Pelnard model. Nevertheless, the use of process based numerical model like XBeach, has been shown to be useful in this type of research. This moreover proves the capability of XBeach model of predicting shoreline evolution and clarifying the mechanism of the natural bypassing process which cannot be achieved by analytical models.
Billy, J., Robin, N., Certain, R., Hein, C. and Berné, S., 2013. Barrier shoreline evolution constrained by shoreface sediment reservoir and substrate control: the Miquelon-Langlade Barrier, NW Atlantic.
The Saint-Pierre-et-Miquelon Archipelago (France) is located in the NW Atlantic Ocean, proximal to the Cabot Straight outlet of the Gulf of Saint-Lawrence, and 50 km south of Newfoundland (Canada). The Miquelon-Langlade Barrier is a 12-km-long, 100–2500-m-wide, north-south–oriented isthmus connecting two bedrock islands (Miquelon to the north; Langlade to the south). This study aims to improve our understanding of shoreface-shoreline sediment exchange processes by comparing medium-term (1949–2011) shoreline changes, determined from aerial photographs and differential GPS data, with total shoreface sediment reservoir volumes estimated using seismic along the west coast of the Miquelon-Langlade Barrier. Spatial variability between the northern and southern sectors of the study site are seen both in the volumes of shoreface sedimentary reservoirs and in multi-decadal shifts of the shoreline position. The northern region has the lowest shoreface sediment volume and the highest rate of shoreline retrogradation. By contrast, the center and southern regions contain the largest volume of sediment in the shoreface and have demonstrated either long-term stability or progradation. This study demonstrates the primary roles of geological control and the distribution of shoreface sediments in local shoreline change at multi-decadal time scales. The sedimentary reservoir, in conjunction with shoreline-monitoring studies and knowledge of transport patterns, may provide a good alternative proxy.
Bryan, K.R. Foster, R., and MacDonald, I. 2013., Beach Rotation at Two Adjacent Headland-Enclosed Beaches
Shoreline rotation occurs on headland-enclosed beaches when the wave climate causes sand to accumulate preferentially on one end of the beach. Past research has shown that these rotation events can occur in response to seasonal variations in the wave climate. Here we investigate 3 years of shoreline variations on two adjacent beaches in New Zealand that are exposed to the same wave climate and tidal conditions, but with different morphodynamic classification. Tairua Beach is approximately 1.2 km long, and is composed of medium-fine sand. Pauanui Beach is approximately 3 km long, and is characterised by lower slopes and finer sand grain sizes. The textural differences are caused by the proximity of Pauanui Beach to the entrance of Tairua Estuary. Both beaches are overlooked by video monitoring stations which collect 15-minute averages of video footage every hour between 2002 and 2004. Shorelines were detected by using the ratio of red to blue light to identify the water-sand boundary. Rotation was quantified by fitting a regression line to the alongshore series of shoreline locations. Results showed that both beaches accreted and eroded by comparable amounts during storm events. However, the rotation characteristics were quite different, with the magnitude of rotation being far greater at the shorter Tairua Beach than at Pauanui. Pauanui responded with a slow rotation over the whole dataset rather than the more event-based rotation that occurred at Tairua Beach. In addition, the two beaches rotated in opposite directions during most of the dataset. A SWAN model was set up to understand the wave induced processes that caused the differences in rotation between the two sites. The model grid was generated from a multibeam survey of the site. The model was set up in a stationary mode providing a solution every 3 hours over the entire duration of the dataset. Results showed that the alongshore wave energy flux was largely controlled by the presence of two offshore islands, Shoe and Slipper island, which caused shadowing of the north end of Pauanui Beach and the south end of Tairua Beach. This in turn accounts for the observed differences in the rotation pattern at the two beaches. These results show that the offshore topography was a stronger control on rotation than overall changes to the alongshore wave energy flux driven by incidence angle changes alone.
Cho, J.H., Cho, J.M., Yun, H.S., Kim, T.W., Kim, C.W., 2013. A Study of Shoreline Changes in Antarctica (Terra Nova Bay) Based on SAR Data
Unlike optical imaging, Synthetic Aperture Radar imaging can produce images regardless of the weather and the time of day, which makes it a useful tool for collecting topographical data in tropical rainforests and in the North and South Poles, where traditional optical imaging is ineffective due to the rapidly changing weather. For this study, this researcher acquired SAR imagery of Terra Nova Bay, located near the South Pole, from October 8, 2011 to March 11, 2012 to observe the changes in its shoreline in summer. SAR imagery was captured once every 11th day to determine the exact time in summer when the glaciers and ice along the shore melt. The acquired stereo SAR imagery data were then processed by applying the radargrammetric method along the shoreline to reduce the speckles specific to the SAR data, and to ensure the accuracy of the coordinates and the size of the satellite imagery, before converting them to DEM at 10m intervals, which again generated orthorectified imagery. The generated orthorectified images were then converted to a digital map with the UTM coordinate system via vectorizing, which visually represented on the map the changes that took place in the shoreline in summer.The study showed that the region was covered with ice from March to early November, which affected the activity in the base, including the access of the ice breaker. Due to the warming climate, there was no sea ice in the Terra Nova Bay for about a month in February. The ice in that area started to melt on November 21 and froze again on February 28. Accordingly, it was concluded that the best time to access the South Pole to build the Antarctic base is mid-December, and the construction crew must evacuate the area no later than March to ensure the safety of the mission.
Coelho, C., Lima, M. and Veloso-Gomes, F., 2013. Relationship Between Cross-Shore Active Profile and One-Line Shoreline Evolution Models Performance
One-line shoreline evolution models, such as GENESIS and LTC, are commonly used to predict coastal configuration changes, where the alongshore sediment transport is controlled by waves, water level, sediments' sources and sinks and sediments' properties. Nevertheless, these models' performance is also affected by considerations related to the definition of cross-shore active profile width, where both models present some differences. In GENESIS, the onshore limit of active profile is defined by the beach berm height, while in LTC, this limit is defined by the wave runup. In what regards the offshore boundary, depth of closure defines the limit in both models. However, GENESIS considers an average value, representing all the waves and all the extension of the modelled stretch whereas LTC allows considering a fixed value, similar to GENESIS, or a variable value depending on each wave height along the time. These considerations have impacts on the definition of the active width of the cross-shore profiles and, consequently, on the shoreline development along time. Thus, in this paper, cross-shore profiles tests are performed, ranging the depths of closure and onshore limits of cross-shore active profiles, in order to evaluate their influence in the shoreline evolution.
Del Río, L., Gracia, F.J. and Benavente, J., 2013. Morphological and evolutionary classification of sandy beaches in Cadiz coast (SW Spain).
Sandy beaches are extremely dynamic systems, so gaining insight about decadal patterns of beach change is essential for the adequate management of risks affecting coastal zones. This work aims at improving understanding of the factors that control erosion-accretion processes and evolution of sandy beaches at the intermediate time scale. For this purpose, recent evolution of beaches along the 150 km long Atlantic coast of Cadiz (SW Spain) is investigated in relation to their morphology and dynamics. Dune toe and high water line changes are assessed based on georectified aerial photographs from 1956–2008, using GIS tools. Results show considerable spatial and temporal variability of recent shoreline changes along the study area, with mostly eroding trends along the northern sector and a predominantly stable southern sector. Important exceptions at certain points are related to the heterogeneity of the coast and the diverse natural and anthropogenic factors contributing to shoreline change in the area. A classification of the studied beaches is proposed, based on beach morphology and dynamics, thus helping to understand the way coastal morphological characteristics influence erosion-accretion trends. Rectilinear beaches are predominantly stable or accreting, whereas reef-supported beaches are mostly erosive. Z-bays generally experience erosion at one end and accretion at the opposite end, greatly influenced by local conditions. Enclosed beaches are stable where sediment budget remains unchanged, but rapidly erode or accrete if human interventions alter the balance. The classification allows identifying those beaches which are most sensitive to variations in controlling factors, such as sediment supply.
Ghionis, G., Poulos, S.E. and Karditsa, A., 2013. Deltaic coastline retreat due to dam presence: The case of river Alfios mouth area, Kyparissiakos Gulf, Ionian Sea.
The deltaic coast of the Alfios river, and especially its mouth area, is undergoing intense erosion over the last decades. This erosion has been caused primarily by the dramatic reduction of the fluvial sediment fluxes, following the construction of two dams (in 1954 and 1967), with the second dam being located at a distance of only 6 km from the river mouth. A further decrease in sediments reaching the sea is induced by the extended (even not continuous) abstraction of sand and gravel from the river's lower route. The resulting sediment deprivation in association with the highly energetic nearshore hydrodynamic regime has caused a retreat of approximately 450 m (from 1945 to 2003) of the mouth area of the R. Alfios. The northern part of the mouth has been affected more heavily by the erosional processes (shoreline retreat between 200 and 445 m) than the southern part (100–240 m retreat), the sediment losses of which are partially replenished by the northward longshore sediment transport of Kyparissiakos Gulf. Shoreline retreat at distances >1 km on either side of the river's mouth is approximately equal, becoming minimal at distances >2 km. The erosional trend of the Alfios River deltaic coast, that has caused significant property losses and damage to coastal infrastructure, is expected to continue and may become more intense as a response to the anticipated future sea level rise.
Goble, B.J. and Mackay, C.F. 2013. Developing risk set-back lines for coastal protection using shoreline change and climate variability factors. Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 2125–2130, ISSN 0749-0208.-->
In a changing climate, coastal zones are increasingly susceptible to coastal hazards. In South Africa this is exacerbated by growing pressure for coastal frontage development. Hence the recognised, urgent need to better control and manage development in the coastal zone. A formal guideline in this regard, is the development of coastal set-back lines to ensure new development is protected from coastal events and slower, climate driven changes. Authorities concerned over potential hazards in the coastal zone are now thinking of how to determine and implement risk set-back lines. This paper presents the stepwise process arrived at, to determine such a risk set-back line for KwaZulu-Natal. The process is simple, cost-effective and considers three key factors; historical shoreline change, sea-level rise and coastal vulnerability. For this study, three set-back line lifespans where considered; 25, 50 and 100 years. This time range allows for both long-term management and short-term understanding of coastal risks and vulnerability. Set-back lines for the three time scenarios range from 0 to 99m, 198m and 394m respectively. The methodology is robust and easily repeatable, and has been designed in such a manner that alternative or additional data can be easily included and the methodology can be refined over time. The delineation and enforcement of risk set-back lines is a quick solution to address the pressing problems of coastal KZN, and should also ensure effective short- to medium-term management of the coast.
Kim, I.H., Lee, H.S., Cho, W.C. and Song, D.S., 2013. Shoreline changes due to groin construction in Namae and Sodol Beaches, South Korea
The present study beach has a long stretch of 5.27km bounded by Namae Harbor in north and Sodol Harbor in south which are located in the eastern coast of Korea. In 2007, a groin was constructed at the southern part of Namae Harbor. In order to analyze the pattern of shoreline change due to the groin construction, a beach survey has been accomplished since 2008 right after the groin construction. The temporal and spatial changes in beach topography are also investigated based on the echo sounding data. The survey data along the coastline showed that a continuous accretion occurred around the groin in the south of Namae Harbor due to the north-directed currents mainly due to diffracted waves formed after the groin construction. Thus the southern beach of study area has been eroded steadily. Also, beach widths and plane area of the beach in the south of the groin were decreased in summer and was increased in winter season. In winter, the ground-based surveying was even impossible due to the severe sand loss in the southern part of study area. Moreover, the survey results revealed that the beach volume was increased and foreshore slope became steeper in 2011 than 2010 survey. Therefore, the continuous beach monitoring along the shoreline is necessary, especially in the seriously eroding beach such as Sodol Beach. More fundamental measures for reliable prediction of potential beach change prior to complementary construction of coastal structures are also needed to maintain the value of the beach.
Gonéri Le Cozannet, Manuel Garcin, Lise Petitjean, Anny Cazenave, Mélanie Becker, Benoit Meyssignac, Patrice Walker, Caroline Devilliers, Olivier Le Brun, Sophie Lecacheux, Audrey Baills, Thomas Bulteau, Marissa Yates, Guy Wöppelmann
Le Cozannet, G., Garcin, M., Petitjean, L., Cazenave, A., Becker, M., Meyssignac, B., Walker, P., Devilliers, C., Le Brun, O., , Lecacheux, S., Baills, A., Bulteau, T. Yates, M., and Wöppelmann, G., 2013. Exploring the relation between sea level rise and shoreline erosion using sea level reconstructions: an example in French Polynesia.
The climate component of sea level variation displays significant spatial variability, and it is now possible to reconstruct how sea level varied globally and regionally over the past half century. The fact that sea level rose faster than the global mean since 1950 in the central Pacific stimulated a study of decadal shoreline changes in this region. Here, the study of Yates et al. (2013) was extended to two additional atolls (17 islets): Tetiaroa and Tupai in the Society islands. Both atolls remain stable on the whole from 1955 to 2001/02, however with significant differences in shoreline changes among their islets and within the period. A modeling of waves generated by historical cyclonic events in French Polynesia since 1970 reveals consistency between major shoreline changes and cyclonic and seasonal waves. As in previous studies, this suggests that waves' actions are a dominant cause of shoreline dynamics on relatively undeveloped atolls, even if affected by higher sea level rise rates. In such regions, numerous joint analyses of shoreline changes and their potential causes may help to explain the relation between erosion and sea level rise.
W.D. Lee, M.K. Kim, D.S. Hur, W.C Cho and J.S. Yoon, 2013 Characteristics of sand transport around the submerged breakwaters installed in Songdo Beach, Busan, South Korean, Journal of Coastal Research, Special Issue No. 65, pp. 2143–2148, ISSN 0749-0208.-->
Songdo Beach, a pocket beach, is directly affected by wave activities. During the First Coast Repair Project (2000–2009), two submerged breakwaters were installed to reduce incoming wave energy and trap the sand eroded from the beach. After that the submerged breakwaters have played an important roll to determine the hydrodynamics behind the submerged breakwaters and the sand transport along the Songdo beach. For these reasons, five-year monitoring (2004–2008) was carried out for the prediction of shoreline change and for the maintenance of shoreline of Songdo beach. On the basis of the accumulated monitoring data, we analyzed the sand movement in Songdo beach to predict beach erosion. The results reveals that beach erosion occurs by the typhoons during the summer season but beach is recovered in its equilibrium during calm wave period. We also analyzed the flow pattern behind the submerged breakwaters to provide the preliminary data for a long-term stability of the shoreline.
Mafi, S., Yeganeh-Bakhtiary, A., Kazeminezhad, M.H., 2013. Prediction formula for longshore sediment transport rate with M5' algorithm
One of the most vital tasks for coastal engineers is to calculate the gross longshore sediment transport rate (LSTR) to control the shoreline erosion and beach evolution. In the past decades, several empirical formulas or parametric models have been proposed for predicting the gross LSTR as a function of the breaking wave characteristics, bed materials and beach slope. The main downside with these formulas is that they give wide range of different rate of predictions; consequently their reliability under the changing hydrodynamic conditions is very uncertain. In the present study, an alternative approach based on the Regression Trees (M5') was applied to present a new formula for prediction of LSTR in terms of the longshore sediment transport coefficient (ϵ). Several high-quality data sets were employed, which comprise of the wave parameters, sediment characteristics and the longshore transport rate. Based on the obtained results, the Shields parameter was selected as the main input variable, while the longshore sediment transport coefficient (ϵ) was given as the output parameter. The M5' algorithm was employed for building and evaluating the regression trees, which showed that regression trees can be used successfully for the prediction of LSTR. Finally, the performance of the new M5'-based formula in the prediction of LSTR was compared with the previous formulas. The results indicated that the error statistics of the regression trees were less and it is evidently predicts the LSTR more accurate than the previous mentioned formulas.
Numanoğlu Genç, A., İnan, A., Yılmaz, N. and Balas, L., 2013. Modeling of Erosion at Göksu Coasts.
Göksu coastal area, located in the south of Silifke County of Mersin on the coastal plain formed by Göksu River, is one of the Specially Protected Areas with an area of almost 15000 hectares and at an altitude of 0–5 m. The Eastern and Western parts of the Göksu river mouth along the Mediterranean coast and the coast of Paradeniz Lagoon are suffering significantly from erosion. As a result of the coastal erosion and the consequent coastal recession problem along the coasts of Göksu, agricultural fields located near the coast are being lost, and especially the narrow barrier beach which separates Paradeniz Lagoon from the sea is getting narrower, creating a risk of uniting with the sea, thus disappearing of the Lagoon. In order to propose solutions for the problem, and to protect the coastal zone and the habitats of Göksu against coastal erosion, coastal dynamic processes and sediment transport characteristics of the region causing the erosion should be investigated and identified. Therefore, longshore sediment transport and suspended sediment transport in Göksu coastal area are examined. First of all, the wind and wave climate of the study area are determined. Then, current pattern, wave propagation, and longshore sediment movements are modeled numerically utilizing three dimensional hydrodynamic transport model HYDROTAM-3D. HYDROTAM-3D is a three (3) dimensional numerical Hydrodynamic and Transportation Model which simulates current patterns due to wind and wave actions, pollutant transport, wave propagation over mild slopes, and longshore sediment transport rates. Model includes hydrodynamics, transport, turbulence, wind and wave climate and wave propagation sub models. HYDROTAM 3D, is developed using “cloud computing” architecture and tightly integrated with Geographic Information System. The study outputs will be used for the determination of the coastal erosion.
Pereira, C., Coelho, C., Ribeiro, A., Fortunato, A., Lopes, C.L. and Dias, J.M., 2013. Numerical modelling of shoreline evolution in the Aveiro coast, Portugal – climate change scenarios
In the Northwest coast of Portugal, the shoreline evolution is leading to several problems, such as loss of territory and infrastructural damages, mainly caused by the sea wave's action. This study aims to predict the impacts of climate change on the shoreline evolution in this coastal area. Coastal stretches studied were Esmoriz-Furadouro and Vagueira-Mira, due to their vulnerability related with the low lying sandy coast, the deficit of sediments, the presence of urban waterfronts and the narrow width of the sand spit that separates the ocean from the Aveiro lagoon.
The paper describes the application of two shoreline evolution models (LTC and GENESIS) to the projection of shoreline evolution between 2010 and 2100. A reference scenario considering the present typical wave climate and the mean sea water level was compared with 3 other future scenarios that may result from climate change effects, combining different wave climates and mean sea levels (0.42 and 0.64 m above present level).
Considering the numerical models' results, maps of the shoreline position were represented every 30 years. The results allowed the analysis of the shoreline retreat, the areas of lost territory and the alongshore sediment transport volumes in several cross sections. A strong trend of shoreline retreat was found for all the scenarios, although the retreat rates tend to decrease along time. Comparing the reference scenario with the climate change scenarios, a slight clockwise rotation of the shoreline was predicted, also increasing the average shoreline retreat from 6% to 11%, depending on the considered scenario.
Pupienis, D., Jonuškaitė, S., Jarmalavičius, D., and Žilinskas, G., 2013. Klaipėda port jetties impact on the Baltic Sea shoreline dynamics, Lithuania.
Port of Klaipėda is Lithuanian Baltic Sea harbour, which construction began in 1835. From 1835 to 2002, Klaipėda port gate (jetties and Klaipėda port entrance channel) saw several stages of reconstruction. Within the last reconstruction works of Klaipėda port gate in 2002, the southern and northern port jetties were extended reaching 1300 m and 1400 m respectively, and the entrance channel was dredged to the depth of 14.5 m. The objective of this paper is to determine the tendencies of shoreline variations in the northern part of Klaipėda harbour, at the Melnragė, on the basis of the analysis of cartographic material from different periods (1835–2010), as well as monitoring data on coastal dynamics (1996–2012) and by applying empirical mathematical functions: the parabolic bay equation. The analysis of cartographic material showed that in the northern part of Klaipėda port at Melnragė (within a sector of 2 km), from 1835 until the end of 19th century shoreline was advancing seaward, and from the beginning of the 20th century until 2002 shoreline was slowly retreating. Since 2002 shoreline erosion has begun, which has particularly intensified in the recent years, i.e. 2010–2012. From 1878 to 2002, the greatest shoreline retreat ranged from 30 to 150 m, whereas in the last two years, shoreline has retreated from 20 to 30 m. It was determined based on field data analysis that the shoreline in the northern part of Klaipėda port develops in accordance with the parabolic bay equation. Also, on the basis of the parabolic bay equation, it was found out that after the jetties' reconstruction (2002) in 2012 the beach static equilibrium was reached. The extension of the northern jetty as well as its new deflection angle determined the change of wave diffractions point position, and consequently led to shoreline retreat and beach bay formation at Melnragė.
Silva, A.N., Taborda, R., Antunes, C., Catalão, J. and Duarte, J. 2013. Understanding the coastal variability at Norte beach, Portugal
Norte beach stands in a coastal stretch fully exposed to the high energetic North Atlantic wave regime. The beach is located updrift of the Nazaré submarine canyon head, a sedimentary sink that captures the southward directed longshore drift. Systematic monitoring of Norte beach has been conducted by a coastal video monitoring system since 2008. A total of 31 monthly coastlines were extracted and analyzed in the period between December 2008 and May 2012. Results show a rare high seasonal coastline variability which exceeds 160 m in the southward sector (adjacent to the headland) and 70 m at the central and north sectors. These coastline variations are related with modifications in the planform beach configuration: beach oscillates between a straight (generally from June to August) and an arcuate configuration (during the remaining months of the year). Results suggest that Norte beach variability depends mainly on longshore drift gradients rather than with cross-shore sedimentary transfers. The intense wave refraction over the canyon head, associated with the westerly swell waves, generates a sedimentary convergence at the centre of the beach promoting the increase of the beach curvature, while, northern and/or short waves (more frequent in summer) tend to linearize the beach. This work contributed with valuable information about the sedimentary dynamics of the Norte beach and showed that this site is a suitable candidate to evaluate longshore drift from shoreline changes.
Splinter, K.D., Davidson, M.A., and Turner, I.L. Monitoring data requirements for shoreline prediction: How much, how long, and how often?
Predicting future shoreline position and the subsequent vulnerability of coastal communities is of great interest to coastal managers and engineers. A number of empirically-based equilibrium shoreline models have been proposed, but all have been formulated on unique and relatively short-term datasets. As such, the transferability and calibration sensitivity of these models is unknown. Here we use a newly developed shoreline model, ShoreFor, driven by changes in offshore wave steepness and wave power, to determine model calibration coefficient sensitivity based on two key constraints in any monitoring program: 1) the duration of data collection of necessary shoreline and wave data (N); and, 2) the shoreline sampling interval (dt). The analysis was undertaken at two distinct sites: a 5-year data set from Gold Coast, QLD, Australia, a long, straight, open coast comprising medium grain sand with a strong annual cycle in the shoreline; and a 6-year data set from Narrabeen-Collaroy, NSW, Australia, which is a coarser, swash-aligned embayed beach whose shoreline variability is driven predominately by storms. In both cases, shoreline data were extracted weekly from video imagery and hourly offshore wave data were obtained from buoy measurements. Shoreline calibration datasets were then sub-sampled in both time (N) and frequency (dt). Results presented in this paper suggest calibration dataset requirements are beach-type dependent and linked to the rates of sediment exchange between the nearshore and shoreline. The storm-dominated site, Narrabeen-Collaroy, required more frequently sampled shoreline data to converge on model free parameters and maintain model hindcast normalized mean square error (NMSE) below 0.5. As a general ‘rule of thumb' a minimum of two years, sampled at dt ≤30 days was required to consistently resolve model coefficients at both sites, while calibration datasets longer than three years (roughly 50% of the data set) resulted in minimal improvement in model hindcast skill at the two sites examined.
Yoshida, J., Udo, K., Takeda, Y., and Mano, A., 2013. Potential impact of climate change at five Japanese beaches
Coastal erosion caused by sea level rise is a serious problem over the world. Future sea level rise will almost certainly accelerate through the 21st century. Although its extent remains uncertain, some predictions expect the increase to be between up to 30 and 180 cm by 2100 (Nicholls and Cazenave, 2010). Several studies show that sea level rise is responsible for long-term beach erosion. Moreover, change of wave height and non-climate-related processes such as ground subsidence amplify coastal vulnerability associated with climate change. It is a pressing issue to predict shoreline change considering the fact that 10% of the global population lives in the coastal regions within 10 m elevation. This study estimates the potential impact of climate change in terms of the effects of: sea level rise; wave height variation; and land subsidence by comparing the past coastline evolutions at five beaches in Japan. The past long-term shoreline change was found to be related to coastal protection measures according to Japan's national policy (Coast Act). Notable erosion was resulted from the construction of coastal facilities that blocked coastal sand drift and the decrease of sediment supply from rivers caused by dam building from 1950 to 1990. Since 1990, shoreline has relatively unchanged because some measures, such as beach nourishment, groins and detached breakwaters, have worked to conserve sand beaches. The estimation results showed that shoreline would retreat over 15 m due to sea level rise and up to 5 m due to wave height variation at the five beaches by 2100. Projection of ground subsidence is uncertain because its rate varies depending on natural forces and human activities. This study suggests that sea level rise would have much greater impact on beach erosion compared with wave height variation and ground subsidence.
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