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Advances in sensor design and data analysis techniques are making remote sensing systems practical and attractive for use in research and management of coastal ecosystems, such as wetlands, estuaries, and coral reefs. Multispectral and hyperspectral imagers are available for mapping coastal land cover, concentrations of organic/inorganic suspended particles, and dissolved substances in coastal waters. Thermal infrared scanners can map sea surface temperatures accurately and chart coastal currents, while microwave radiometers can measure ocean salinity, soil moisture, and other hydrologic parameters. Radar imagers, scatterometers, and altimeters provide information on ocean waves, ocean winds, sea surface height, and coastal currents, which strongly influence coastal ecosystems. Using airborne light detecting and ranging systems, one can produce bathymetric maps, even in moderately turbid coastal waters. Since coastal ecosystems have high spatial complexity and temporal variability, they frequently have to be observed from both satellite and aircraft in order to obtain the required spatial, spectral, and temporal resolutions. A reliable field data collection approach using ships, buoys, and field instruments with a valid sampling scheme is required to calibrate and validate the remotely sensed information. The objective of this paper is to present an overview of practical remote sensing techniques that can be used in studies of coastal ecosystems.
Over the next century, ongoing coastal change will require a change in the way flood and erosion risks are managed in some areas. Such changes may have significant effects on local stakeholders and may require varying degrees of adaptation. It is therefore important for these stakeholders to be able to enter fully into the consultation process associated with these issues. This paper describes an innovative approach to stimulate public debate and improve stakeholder understanding of the issues that need to be balanced in order to achieve sustainable long-term coastal management solutions. The approach involves the creation of an educational tool (CoastRanger MS) that allows users to manage a virtual coast within a PC-gaming–type environment. CoastRanger MS incorporates a legacy of past developments and defences, and uses a coastal process simulator to predict the impacts of climate change under different management scenarios chosen by the user. In the UK, it is anticipated that the tool will be of particular value in educating stakeholders before and during the development of strategic coastal management plans.
In order to have an understanding of the coastal processes along the southwest coast of India (8°4′ N, 77° 33′ E to 8°13′ N, 77°14′ E), a data set available for the changes in beach width for a period of 5 years (1993–1998) over a length of about 50 km was categorized and analysed in relation to the seasons. Since the study area is densely populated and was also affected partially by the great Indian Ocean tsunami, a fresh measurement campaign of beach profile changes up to a water depth of 6 m at four different locations along the coast was carried out. These measurements have been adopted to validate a finite difference–based numerical model that employs the empirical formulation of Larson and Kraus (1989) for the prediction of beach profile changes. We simulated the offshore wave climate from National Centre for Environmental Prediction wind data using the Wave Analysis Model (WAM), whereas the nearshore wave climate was derived by adopting the MIKE21 Parabolic Mild Slope module. Results compared well with each other. The prediction from the numerical model revealed that the average onshore-offshore transport varies from about 50 to 200 m3 y−1 m−1 width of the beach.
A 6-year survey (1993–1998) is summarized for fish collected from chemically contaminated, urbanized bayous in northwest Florida. Fifty-two monthly collections (January–November) using trawls and seines occurred at 22 sites located in three adjacent bayous associated with the Pensacola Bay Estuary. Hurricanes Erin (Category 2) and Opal (Category 3) made landfall near the study area, and a state-wide entanglement net ban was initiated during the survey period. Approximately 585,000 fish were collected, which represented 80 species and 66 genera. The assemblages were dominated by estuarine-dependent and resident species similar to those commonly found in several nearby estuaries. Of these, Leiostomus xanthurus, Brevoortia patronus, Anchoa mitchilli, Lagodon rhomboides, and Menidia peninsulae composed 95% or more of the total catch. The total number of species for each collection ranged from 8 to 23, total abundances varied from 140 to 14,315 individuals, and Shannon diversity index values (H′) were between 0.02 and 0.97. Mean species numbers and diversity index values were more consistent monthly than fish total abundance, which was influenced by seasonal occurrences of estuarine-dependent species. Hurricane effects were specific to the hurricane, structural parameter, species, and bayou. The posthurricane reductions in salinity (17% to 69%) and the few changes in fish abundance were usually temporary and within monthly and interannual variability. The resiliency of the fish assemblages to natural and anthropogenic stresses represents a survival advantage and readiness for future climatic change.
The influence of waves and tides on the development of coastal cliffs has long been recognised as an important contributor to long-term coastline evolution. However, the relationship between the assailing force of waves and the resistance afforded by foreshore and cliff material that governs the processes through which cliff change occurs remains inadequately quantified and poorly understood. This is further confounded by a limited appreciation of the interplay between the coastal landforms and the range of processes that control their evolution. To explore this, we compare microseismic ground movements resulting from wave impacts to the occurrence of rockfalls from a section of cliffs on the North Yorkshire, United Kingdom, coastline. The results indicate that critical tide levels exist at which waves, in combination with wind directions coinciding with the greatest fetch, generate notably higher levels of energy delivery to the cliff face and that these levels, in turn, correspond to increased levels of material detachment from both within and above the cliff toe. Foreshore microtopography is shown to have a significant influence on wave energy flux and impact timing at the cliff face. The link between relative sea level and geomorphological work done by wave action is both spatially heterogeneous and tightly constrained by foreshore topography, yet local scale topographic controls are rarely considered in scenarios of future coastal change. The timing of relative increases in rockfall activity is also shown to correlate with preceding seismic events, which may indicate a lag or threshold in the geomorphic response of the cliff. Finally, the article uses modelled increases in inundation to explore the influence of topography on the distribution of changes to the tidal regime under future sea-level rise scenarios. These data highlight the need for a greater understanding of cliff behaviour if, in the context of sea-level rise, future coastal evolution is to be predicted.
KEYWORDS: estuary, intertidal flat, numerical modeling, Anthropogenic Influences, water exchange, tidal prism, return flow factor, average residence time, mixing factor, Jiaozhou Bay, China
The tidal-driven flow field and average residence time for water in Jiaozhou Bay in the years 1966, 1988, 2000, and 2008 were investigated using the EFDC (Environmental Fluid Dynamics Code) with a coupled dye module. Jiaozhou Bay (JZB) in northeastern China is a semi-enclosed shallow bay that has undergone large-scale land reclamation over the last four decades, especially over the extensive intertidal flats. Data from field observations were used to calibrate and verify the EFDC model for JZB. The verified JZB model was used to study spatial variations of flow field and water exchanges from 1966 to 2008. The overwhelming influence of human activities, especially land reclamation, is the main cause of the significant changes in hydrodynamic conditions and water exchange in JZB. The human-induced changes of the coastline position-configuration and nearshore bathymetry have resulted in substantial changes in the residual current patterns, especially in Qianwan Bay, Haixi Bay, and northeastern Jiaozhou Bay. The overall tidal prim of JZB has been reduced by 26% as compared to that in 1928. This is considerably less than the 35% reduction obtained by other studies. The decreasing water-exchange ability corresponds to an increasing average residence time (ART) over the past several decades, particularly after the 1980s. In addition, the influences of the return flow of the bay water from the open sea back into the estuary were quantified by determining the return flow factor for each year. An existing tidal prism model was revised by introducing a mixing factor κ, and a simplified formula was developed for JZB. The revised tidal prism model suggests continued deterioration in water quality and exchange ability of Jiaozhou Bay in the near future.
Environmental fluid dynamic code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of the salinity, temperature, nutrients, and dissolved oxygen (DO) in Perdido Bay and adjacent Gulf of Mexico. External forcing factors included the coupled effects of the astronomical tides, river discharge, and atmospheric winds on the spatial and temporal distributions of salinity and DO. Modeled time series were in good agreement with field observations of water level, nutrients, temperature, salinity, and DO. Perdido Bay and adjacent northern Gulf of Mexico coasts can be divided into two areas according to salinity, water level, and DO concentrations. The first area was lower Perdido Bay and the associated Gulf of Mexico coasts, acting primarily under the influence of tidal forcing, which increases the vertical stratification. The second division was upper Perdido Bay, which was influenced by both tidal forcing and freshwater inflow. Simulations also indicated winds influenced the salinity and DO distributions, with an enhanced surface pressure gradient. Tidal effects were also important for conducting salinity and water quality simulations in Perdido Bay. Low amplitude tides induced relatively weak vertical mixing and favored the establishment of stratification at the bay, especially along deeper bathymetry. Flood tides influenced the distribution of salinity and DO more than ebb tides, specifically along shallow bathymetry.
During the last decade, global tidal models have spectacularly improved. However, they still have difficulties in resolving tides over continental shelves and near coastlines. This study of tidal propagation from the continental shelf to the North Patagonia Gulfs of Argentina applies a set of three nested high resolution models based on the Hamburg shelf ocean model (HamSOM), where particular attention was paid to the bathymetry and the coast line. The study is complemented by the use of all the tidal gauge and tidal current observations available. Simulations display good agreement with observations, permitting the construction of higher resolution and more reliable cotidal and corange charts. The tidal regime in the area is essentially semidiurnal and dominated by M2. This constituent propagates northward as a Kelvin wave and reaches the gulfs from the south. In their interior an important amplification is observed. Tidal currents are large at the mouths of the gulfs, and weaken toward their interior. The nonlinear transfer of energy from the semidiurnal to higher order harmonics was analyzed. This can be very important in the interior of the gulfs, particularly in Nuevo Gulf and in the northwestern San Matías Gulf, close to San Antonio. Energy flux and energy dissipation by bottom friction has been computed and indicate that this region dissipates 17% of the total energy dissipated on the Patagonian Shelf which, in turn, is one of the most dissipative areas of the world ocean. The Simpson-Hunter parameter computed from the simulations shows that in the mouth of the gulfs, particularly in San Matías and east of the Península de Valdés, the tides are energetic enough to overcome stratification and produce tidal fronts. The locations where tidal fronts are located are highly consistent with results from sea surface temperature and primary productivity data analyzed by other authors.
St. Catherines Island, located off the coast of Georgia (United States), has been inhabited by humans for close to 5000 years. The island's long-term habitation and varied history of land use has left a legacy of anthropogenic impacts that has strongly influenced the composition and function of the current vegetation communities and underlying soils. In this study, we examined the chemistry of surface soils collected from 32 sites representing five historical land uses (old cotton plantations, longleaf pine savanna, hickory forest, maritime forests, and shell middens) to determine how human activities have affected the island's surface soils. We found that shell deposition left a strong chemical signal, significantly increasing soil pH, cation exchange capacity, and concentrations of Ca, total nitrogen, and several micronutrients. Soils under the hickory-dominated forest had chemical characteristics that were intermediate between the middens and the other three cover types. Despite a wide range in pH, all sites had very high concentrations of extractable P, possibly because of retention by Ca and Fe. Shell deposition has altered soil chemistry in numerous areas across the island, and this has important implications for soils and the resultant vegetation patterns currently seen along St. Catherine's coastlines as well as other coastlines throughout the world.
The armor layer on the sea side of a rubble structure must be designed to protect against incident waves during storms. Formulas for armor stability and damage progression have been developed and are widely used for practical applications. However, none of the formulas accounts for the water depth at the toe of the structure explicitly. An alternative approach based on the maximum wave momentum flux at the toe of the structure is proposed in this article. Equations for sizing stable armor stone for constant incident waves and water level are proposed and calibrated using available data. Equations are also developed for determining damage progression in a life-cycle analysis involving varying wave and water level characteristics. The developed equations are calibrated using the damage progression tests conducted previously by the authors and verified using an additional 10 tests conducted for this article.
The Patos Lagoon is located in the southernmost part of Brazil, between 30°–32° S and 50°–52° W, being connected to the South Atlantic Ocean via a narrow channel that is less than 1 km wide. The lagoon drains a hydrographic basin of approximately 200,000 km2, and its principal rivers contribute with an annual mean discharge of about 2000 m3 s−1. In this work, the dynamics of the Patos lagoon coastal plume was studied considering theoretical situations that determine the relative importance of Earth rotation, river discharge, tides, and winds. To carry out this analysis, the finite element model TELEMAC2D was used for the experiments. The results show that Earth rotation is very important in generating asymmetry in the plume flow. Tides are important for the mixing processes, causing an increase of the plume area and a decrease of the plume penetration offshore. In addition, results also showed that northeast winds displace the coastal plume southward, which is likely to be related to the formation of mud banks south of the Patos Lagoon mouth. During southwest wind events, the mixing zone moves landward, being observed inside the access channel, while part of the coastal plume remains in the coastal zone and is directed northward as a coastal current.
The Coorong is an elongated coastal lagoon system in southern Australia whose major freshwater input occurs through a series of barrages separating it from an adjacent lake. The connectedness of the lagoon to the sea continuously evolves as its Mouth channel is scoured by sustained outflows associated with barrage discharges or is infilled with sand during times of zero flows. A key driver of the Coorong dynamics is oceanic water-level fluctuations propagating into the lagoon, and the representation of the continuously changing transmission properties of the Mouth channel for these fluctuations is a necessary requirement for the successful modelling of these dynamics. This paper applies a methodology for estimating the effective bed elevation and width of the Mouth channel by considering how oceanic water-level fluctuations propagate into the Coorong. The analysis applied to 22 years of measurements shows how the effective depth of the Mouth channel has been highly dynamic, varying between more than 5 m to less than 0.5 m depending on barrage flows. A simple algorithm is developed that well represents the time series of effective bed elevations as a function of Mouth channel outflow. This algorithm enables the hydrodynamic modelling of the Coorong to be undertaken to assess the impact on the lagoon of alternative barrage release strategies.
Parallel implementation of an unstructured Simulating Waves Nearshore (SWAN) model with the Wave Model (WAM) cycle 4 formulation was used to evaluate the performance of a third-generation wave model over large spatial scales. Data from a network of National Data Buoy Center (NDBC) buoys and the Wave Current Information System (WAVCIS) stations were used to assess the skill of the input and output of the wave model. The simulation results reveal that the underestimation of energy in the low-frequency band (0.12–0.17 Hz) can be ameliorated if the model is calibrated using site specific in situ measurements instead of the Pierson-Moskowitz spectra. This process led to more than a 25% decrease in the root mean square error between simulated significant wave height and in situ observations. Use of the verified model for the Gulf of Mexico, with bed friction computed from grain-size distribution, as opposed to a default constant bed-friction formulation, showed that the wave height difference can exceed 1.5 m or 40% of local wave height for a large spatial extent during extreme events, such as Hurricane Dennis. In addition, with the use of eddy viscosity bed-friction formulation with usSEABED (U.S. Geological Survey), the sediment data results were in better agreement with the in situ observations during Hurricane Dennis, with less than a 4% increase in computational cost. The mean wave-height distribution over several cold fronts also demonstrates the influence of bed grain-size parameterization in wave transformation, especially in water depths shallower than 15 m, thereby demonstrating the significance of this study in advancing our understanding of sediment-transport modeling.
Geological investigations conducted over a vast seabed offshore the giant Saemangeum Dike on the west coast of Korea indicate that the surface area of fine to very fine sands has rapidly expanded southward in recent years (2002–2008). To unravel the processes responsible for this phenomenon, two field campaigns of hydrodynamic measurements were carried out at the same station with an instrumented tripod during May 2007 and January 2008. The measurements show the definite occurrence of wind-generated residual currents that were more distinctive and consistent during winter compared with the relatively weak, inconsistent analogues of the late-spring season. The simple algebraic calculations for bedload transport based on a cubic relationship between the bedload transport rate and steady currents suggest that the southward movements of surface sands result from interplay of wintertime residual currents and macrotidal currents. In addition, numerical model experiments illuminate that the dike construction has increased the N-S component of tidal currents over the study area. The sediment transport evaluations further suggest that this artificial increase in tidal currents in the N-S direction could considerably enhance southward sand transport.
As coastal development becomes increasingly threatened by erosion, installation of armoring such as seawalls has been applied to protect property by permanently relocating the position of a dune. The physical impact of seawalls to beach ecosystems is relatively well-understood, but the impact to sea turtle nesting remains unclear. We investigated the impact using observations of loggerhead sea turtle nesting in Florida at a seaward wall over 7 years, and a more landward wall over 3 years. Nesting patterns indicated that passive erosion at seawalls likely caused fewer turtles to attempt to nest on armored beach when compared with unarmored beach. Nests placed in front of seawalls were more likely to be washed away in storms. Placement of walls further from the shoreline may only delay the impact to nesting turtles by a few years. Armoring is expected to multiply as sea levels rise and storms become more frequent; thus, the availability of appropriate nesting habitat for loggerhead sea turtles remains at risk.
The İğneada area of Turkey includes different ecosystems and a wide range of biodiversity, making it one of Turkey's most important areas. İğneada and the surrounding environment have unique characteristics; in other parts of Turkey and Europe, the types of wild forests found in the İğneada area have been damaged by anthropogenic effects. Lakes Mert and Erikli in the İğneada area play an important role in the formation and maintenance of the Longos forest. This study used Landsat Thematic Mapper satellite images from 1987 and 2009 and 1 ∶ 25,000-scale topographic maps. The satellite images were geometrically corrected and underwent image processing and classification, and the results were subsequently calculated using reclassification and overlay analyses. In addition, a rapid ecological assessment was carried out to detect changes in the field. The surfaces of lakes Mert and Erikli were found to have decreased by 4.03%. The reason for this minor change is that the flow rates of streams feeding these lakes are well protected. The primary cause of the observed changes was found to be the amount of seasonal precipitation and the amount of water taken from the rivers feeding these lakes.
Because invasive species are a major threat to global biodiversity, understanding the factors influencing the invasibility of native communities and documenting effects of invasive species on native communities is important. In this study, we assessed the role of disturbance in mediating the invasion of Asiatic sand sedge, Carex kobomugi Ohwi (Cyperaceae), in New Jersey's coastal dune ecosystems. Stem densities and species richness of native plants were significantly lower within areas invaded by C. kobomugi than in surrounding areas. Species diversity and species richness inside invaded areas at two highly disturbed sites were similar to one another and significantly lower than those in a less-disturbed site (two-way analysis of variance, Wilks' λ F = 8.4, degrees of freedom [df] = 78, p < 0.001), suggesting that disturbance enhances the ability of C. kobomugi to outcompete native plant species. A significant correlation between native plant stem densities inside invaded areas and those in surrounding areas suggests that preexisting habitat characteristics also play a role in driving observed differences in native plant densities at each site. However, the lack of a significant relationship between species richness or species diversity inside invaded areas compared with nearby uninvaded areas, suggests that C. kobomugi may be more important than background heterogeneity in influencing both those parameters. No clear differences were found between species richness, diversity, or native plant stem densities based on population size. This may mean that the impact of the sedge does not increase between early and late stages of the invasion. Alternately, it may mean that population size is a poor proxy for invasion maturity.
A large database of deep water wave buoy measurements over a 24-year period is created for four regions comprising the West Coast of the United States. The regional monthly mean significant wave height (MMSWH) is selected as the defining wave climate parameter and averaging multiple data sources within a region is found to significantly reduce data gaps. Two 12-year periods are compared, showing significant temporal variability but high correlation between regions, allowing the further collapse of the data to a northern and a southern region. Correlations between MMSWH records with three global-scale climate indices are investigated and only the North Pacific Index (NPI), a measure of atmospheric pressure in the Gulf of Alaska, shows strong correlation. The Multivariate ENSO Index (MEI) is less correlated and the Pacific Decadal Index (PDO), which is a measure of ocean surface temperature, provides no significant correlation.
A method for displaying multiple correlations is developed that shows the mean of all MMSWH records that occur at unique temporal combinations of two climate indices. The graphics depicting the mean wave height as a function of NPI and MEI for the two 12-year periods are shown to be very instructive in establishing why the two periods are so different. On the contrary, the same procedure with PDO substituted for MEI produces uniform distributions with little interpretive value.
Century-scale variation in the climate indices is investigated, and significant linear trends are found for NPI and MEI, both consistent with causing increases in mean wave energy in these regions. Causal relationships for the observed correlations are discussed, and conclusions are reached indicating that global warming is a likely contributor to observed increases in wave intensity in the North Pacific.
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