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O Rostro beach was one of the most seriously affected beaches during the Prestige oil spill along the “Costa d'a Morte” in Galicia, Spain, in November 2002. More than 10,000 tons of residual material were removed from the beach, with a significant quantity of the oil buried in the sandy sedimentary column of the beach. Under sporadic wave conditions throughout the years, this situation made the clean-up activities very difficult. Among the reasons why a significant quantity of oil was buried in the beach are the following: first, the arrival of large quantities of oil to the beach; second, an elevated number of high wave energy storms with atypical sequence in direction; and third, the particular morphodynamic features in O Rostro Beach, which is an intermediate bayed beach with a stable middle-scale transversal bar-horn system that, interacting with the local dynamics, has a high capacity to bury oil in sand matrix (2 to 3 m deep). The information collected in the 3-year exhaustive monitoring plan (spring 2003 to summer 2006) in O Rostro Beach has provided better knowledge and comprehension of the processes involved in the interaction of the oil spill dynamics with the beach morphodynamics. Based on these field data, the zones with deeply buried oil were located; also, it was evidenced that 4 years after the oil spill, the buried oil degraded rapidly. A conceptual evolution model of the oil leaked to the beach is proposed, with the aim of explaining how and where the oil initially arrived, where it was buried in the sandy core, and how the oil has evolved physically and mixed with sand throughout the last several years. Based on the conceptual evolution model of the oiled substance, the morphodynamic characterization of the beach, and the field data collected, the clean-up activities have been optimized and significantly improved in O Rostro Beach.
KEYWORDS: Chesapeake Bay, United States, Delaware Bay, Kings Bay, Australia, Laguna Madre, Mexico, Maputo Bay, Mozambique, Pamlico Sound, Spencer Gulf, low-energy coastline
There are more than 15,000 barrier islands in fetch-limited nearshore environments around the world. About half that number are actively evolving (eroding, accreting, migrating) in response to oceanographic processes and are the subject of this study. The remaining half consists of inactive islands protected by surrounding salt marsh or mangroves. Despite their global abundance these islands have not been previously systematically studied or even recognized as a major landform type. More than 70% of fetch-limited barrier islands are found on trailing edge coasts because conditions there are favorable for formation of sheltered waters. Fully 50% are found in the coastal zone of Australia, Mexico, and Russia. We identify eight different types of fetch-limited barrier islands based on genesis and mode of occurrence. Most of the active islands form in estuaries or bays (Spencer Gulf Australia), behind open ocean barrier islands (Pamlico Sound, North Carolina), or on flood tidal deltas of open ocean tidal inlets (Tapora Bank, New Zealand). Others occur on river deltas sheltered by offshore islands (Menderes Delta, Turkey), in sheltered bays with thermokarst topography (Yensei Bay, Russia), and on glacial outwash plains in fjords (Golfo Esteban, Chile). Due to a Holocene sea level drop, some southern hemisphere islands have been stranded above mean sea level and are intermittently active (Maputo Bay, Mozambique); they are only surrounded by water during spring tides and storms. Intermittent islands also form under conditions of high tidal amplitude (Kings Bay, Australia). Fetch-limited barrier islands are much smaller than their open ocean counterparts, averaging roughly 1 km long and 50 m wide and 1 to 2 m maximum elevation. They evolve in similar fashion to ocean barriers except that overwash is almost always the dominant island building process and dune formation is much less important. The two biggest distinctions between open-ocean and fetch-limited barrier islands are (1) complete evolutionary dependence on storms and (2) the important role of salt marsh and mangrove vegetation in controlling the shape and location of fetch limited barrier islands. Stabilized by salt marshes and mangroves, vegetative control is responsible for the irregular shape of some fetch-limited barrier islands and often plays a role in creating the foundation upon which the island evolves. Few of these islands are settled or developed at present, but it is likely that in midlatitudes they will soon be under development pressure.
Thalassotherapy is perhaps less an alternative medicine than a treatment for specific ailments. It has witnessed ups and downs. A centuries-old, if not millennia-old, approach, it has gained many adepts in the medical profession and left many a patient delighted with its results. Thalassotherapy has many aspects in common with thermalism that, similarly, gained its lettres de noblesse over the centuries. This paper examines the roles that thalassotherapy has played and currently plays and surveys the European centers that have gained a solid reputation for thalassotherapy. It concomitantly considers its parallel therapy—thermalism—and takes a look at other related alternative or complementary treatments. The economic impact of thalassotherapy and its related activities has increased.
Human predation has affected population size structures (in the sense of distribution of body size within particular populations), which has been used to track losses of larger and more fertile individuals from populations. In this sense, human exploitation can also decrease the reproductive output of invertebrate populations such as the endangered limpet Patella ferruginea. A total of 7077 individuals of this protected limpet were analysed among “Under custody” and “Without custody” sites, the strongest indication of human exploitation being the absence of a great number of larger limpets at “Without custody” sites. Likewise, recruitment was lower in “Without custody” than in “Under custody” sites, although the mean density was not affected. The presence of 4084 individuals inside the harbour area of Ceuta indicates the requirement of the involvement of harbour authorities and environmental agencies in a global conservation plan, establishing small fenced reserve areas in artificial breakwaters and natural substrates where dense populations are settled. These reserves could be useful as a focus for larval export via their previous rebalance of sex ratio.
The objective of this work was to study the dynamics of the level of organic versus inorganic contaminants in oysters following a significant spill of 15,000 t of heavy oil in the Eastern Mediterranean. Twenty oysters were harvested from each of six selected sites at 72 and 305 d subsequent to the oil spill. Results showed a significant decrease over time in the mean of the means of organic contaminants in oysters (total polycyclic aromatic hydrocarbons [TPAH]: 0.354 vs. 0.177 μg g−1 dry weight, P < 0.05; total polychlorinated biphenyl [TPCB]: 0.031 vs. 0.021 μg g−1 dry weight, P < 0.05). Conversely, the mean of means of each of three heavy metals showed a significant increase over time (P < 0.05) (lead [Pb]: 2.791 vs. 3.543 μg g−1 dry weight, P < 0.05; nickel [Ni]: 6.732 vs. 17.682 μg g−1 dry weight; vanadium [V]: 1.874 vs. 15.833 μg g−1 dry weight). The importance of this pattern in oppositional dynamics of organic versus inorganic contaminants in oysters is discussed.
Quantification of the sediment transport processes in the Fort Pierce Inlet, Florida area and the influence of the inlet onto the adjacent beaches was performed by means of analytical methods. This analysis is formalized as a sediment budget and is based on available survey data, nourishment events, and dredging records of the navigational channel at Fort Pierce Inlet, which cover the period from 1972 to 2002. Available survey data encompass shoreline distances approximately 9.7 km north and 24.7 km south of Fort Pierce Inlet. Three intersurvey periods were examined in this study: 1972 to 1987, 1987 to 1997, and 1997 to 2002. Average annual sediment volume and shoreline changes derived from the profile data collected during these three periods were analyzed. Application of general sediment budget principles established that for the total period from 1972 to 2002, there was an average annual deficit of approximately 12,500 m3/y on the beach south (downdrift) of Fort Pierce Inlet. The general sediment budget suggests that 88,700 m3/y enter the north boundary of Riomar Beach some 18 km north of the inlet; 62,700 m3/y enter the north boundary of St. Lucie County some 10 km north of the inlet; and 43,600 m3/y leave the south boundary of St. Lucie County some 25 km south of the inlet. Application of numerical modeling to develop an understanding and predictability of the performance of beach nourishment south of the inlet was carried out as a supporting method to better understand the littoral processes in the area. Recommendations to improve the sediment management practices, including sand bypassing to restore balance to the south beaches, are presented.
The purpose of this study is to analyse the shoreline response of a beach protected by a system of low crested structures (LCS) and to apply the results to the management of coastal stability problems. This contribution aims to provide heretofore scarce detailed data and observations of the shoreline variability of coasts protected by LCS. These aims are acheived by selecting and monitoring the appropriate Coastal State Indicator (CSI) to describe the state of the beach. The CSI used is the Mean Intertidal Position (MIP), which has been detected by the ARGUS system installed in Lido di Dante, Italy.
The error in the shoreline estimation from video was assessed by comparing shorelines detected with global positioning system (GPS) and image analysis over a large number of cases. The horizontal error in the shoreline detection is estimated to be on the order of 0.90 ± 0.74 m, which is acceptable because it is on the same order of magnitude as the swash width.
The MIP, which has been monitored over a forty month period with elevated spatial and temporal resolution, was monitored in several transects of the beach protected by a system of LCS and boundary groins, creating two cells. The behaviour of the section in the middle of the cell was comparable to the behaviour of the total beach. Results were analysed with respect to the fixed beach state of the initial beach position (January 2004). The MIP regression rate is around 2.3 m/y, which is modest considering the local subsidence magnitude (1.8 cm/y). Therefore, the actual data do not show any evidence of immediaste risk, either for the present structures on the beach or for the infrastructure immediately behind; however, the results do show a risk for the sustainability of the characteristics that permit tourist development. The use of video-derived CSIs is confirmed to offer a valuable tool for coastal management.
We describe a seven-camera video system deployed at Rehoboth Beach on the Atlantic coast of Delaware that was used to monitor and quantify the evolution of a nourished beach. Shorelines along 6 km of beach were automatically identified using pixel-intensity gradients from time-exposure and variance imagery. Correlations between automatically identified and user-defined shorelines from images with various wave and atmospheric conditions exceed r2 values of 0.92. Small variations in camera azimuth and tilt were found to significantly affect apparent shoreline locations and were automatically corrected through image-correlation procedures. Hourly shoreline data were tidally and seasonally averaged to quantify seasonal morphodynamic variability. Over a summer-winter-summer monitoring period, the shoreline exhibited erosional and accretional variations of ∼10 m dependent in the alongshore direction on permanent man-made structures and subject to seasonally characteristic littoral transport variations. A comparison of mean seasonal shoreline locations revealed a mean erosion value of ∼0.8 m between the summer of 2006 and the summer of 2007; this erosion rate is consistent with previous studies of this area. The temporal history of the planform area, obtained from shoreline position, showed weak correlation with volumetric measurements and thus could not be used as a proxy for volumetric change at this site.
To quantify the trapping effect of tidal marsh vegetation on suspended sediment, we measured the amount of sediment adhering to three species of plants in different habitats in the Yangtze Delta. We also measured suspended sediment concentrations (SSC) and bed levels in the tidal marsh to examine their influence on the adherence of sediment to vegetation and the contribution of vegetation-trapped sediment to the local total deposition rate. The results include (1) the density of sediment trapped in the joints of leaves and stems and on fruits, which was 5 to 10 times higher than that on the stems and leaves; (2) the amount of sediment (18 to 559 g/m2 in dry weight) trapped by vegetation, which increased with plant biomass (220 to 5408 g/m2 in dry weight); (3) the dry weight of sediment adhering to plants, which drastically decreased from 10–15 g/m2 to <2 g/m2 upward from their base to their tip; (4) the amount of sediment trapped by vegetation per unit land area in the low marsh margin, which decreased at a rate of 1% to 3%/m with distance from the outer marsh edge, bordering the mudflat, or from the tidal creak, where the SSC was higher; and (5) the amount of vegetation-trapped sediment, which was likely responsible for >10% of the total depositional rate in the Spartina alterniflora marsh and <10% of the total depositional rate in the Scirpus mariqueter marsh. It was concluded that the amount of sediment trapped by the tidal marsh vegetation was related to plant properties, to the SSC, and to the bed level, which determines the tidal submergence; the introduced S. alterniflora is significantly more efficient in trapping suspended sediment than the native Scirpus and Phragmites plant species.
Ensemble-averaged suspended sediment concentrations (SSC) and transport from the swash zone of a high-energy beach are investigated with respect to the time-averaged setup level obtained from calibrated video records. Ensemble-averaged data indicate variability in SSC between both uprush and backwash during rising and falling tides. Mean ebb-tide SSC exceeds mean flood-tide SSC during both the uprush (by 28–34%) and backwash (by up to 25%). Suspended sediment concentration also varies between swash phases over a tidal cycle with mean uprush SSC exceeding mean backwash SSC by 46% to 108% depending on tidal level, with a general percentage decrease during the falling tide. The net ensemble-averaged transport (velocity-SSC product) magnitude displays a decreasing trend from roughly 30 to 20 kg m−1 during the rising tide and from roughly 45 to 15 kg m−1 during the falling tide that cannot be explained based on the percentage of foreshore immersion (water depth) alone. Thus, relative tidal level (cross-shore instrument position within the swash zone) and the phase of tide (rising or falling) within the swash zone play an important role in determining the magnitude of sediment suspension and transport.
The purpose of this study was to characterize mangrove-derived organic matters in wetland sediments and to establish a quantitative differentiation between mangrove-derived organic matter and other organic matter source(s) in the Zhangjiang Estuary mangrove wetland, southern China. Total organic carbon, total nitrogen, carbon/nitrogen ratio, and stable carbon isotopic compositions were measured in surface sediments, three sediment cores (in pure forest of Kandelia candel, Aegiceras corniculatum, and Avicennia marina, respectively), and mangrove plant samples collected from mangrove wetlands. A mixing model was applied to calculate the contribution of the mangrove-derived organic matter in sediment. The mangrove-derived organic matter in three sediment cores from the mangrove wetland were distinguished quantitatively. Our results indicated that organic matter preserved in the sediments was not predominantly composed of the mangrove-derived organic matter in the study areas. The in situ contribution of mangrove plant carbon to sediment organic matter differed between the three core samples. The composition of the mangrove-derived organic matter is 6.36%, on average, in K. candel pure forest, which is much lower than the values in A. marina and A. corniculatum pure forest (21.95% and 36.88%, respectively).
Four current time series, collected at costal locations of the San Matías and San José gulfs, Argentina, are analyzed for tidal and residual currents. Tides dominate San Matías Gulf dynamics, accounting for more than 72% of the variance, whereas winds dominate at San José Gulf, explaining approximately 70% of the variance. Tides display a dominating semidiurnal regime, in compliance with what is know from the few tidal stations available and numerical simulations. At San Matías, coastal tidal currents speed increases northward, exceeding 0.6 m s−1 at San Antonio Este. Higher order harmonics because of nonlinear interactions are large; in every sampled site, M4 and M6 currents are stronger than the diurnal constituents and have amplitudes around 5% of those from M2. At Las Grutas (San Matías Gulf), simultaneous wind observations were collected. Currents respond almost instantaneously to wind variability in the form of two modes. The first one results from winds blowing along the northwest–southeast axis and is very weak; the second one results from winds blowing from any other direction and is characterized by strong meridional currents. Even though bimodal patterns are typical of semienclosed basins, the characteristic wind directions in this gulf are not related with the orientation of its mouth but could result of the circulation in the form of two gyres suggested by numerical simulations. Energy peaks are observed at the 4 to 8 days' band and at around 12 and 20 days. Therefore, currents rapidly respond to wind variability in every timescale, from synoptic to intraseasonal.
This article highlights the impact of tidal inlet modification on the evolution of inland estuarine waterways at the short–medium timescale. The study area is the Nerang River estuarine system located on the east coast of Australia. This estuary has been affected by a range of developments, including stabilization of its tidal entrance. This study is mainly focused on quantifying the tidal regime change and potential morphological and ecological implications resulting from these changes. To this end, the study started with field data collection and numerical modelling of the study area. The results of harmonic analysis showed that the Nerang Estuary responds nonlinearly to tidal forcing and is dominated by frictional forces. Analysis of water level and current time histories showed a mixed, predominantly semidiurnal, and flood-dominant tidal regime within the estuary. It also showed strong asymmetry of tide along the estuary. At the second stage of the study, historical data of the study area were analyzed and compared with the recently collected data. The purpose of this stage of the study was to understand the evolution of the estuary as a result of the changes at its entrance over the past 20 years. Variations in the ratio of amplitudes from M4 to M2 demonstrate that the Nerang Estuary nonlinear response to tidal forcing has reduced over the past 20 years. Analysis of historical data also suggests that the estuary has become less flood-dominant over the past 20 years, and as a result, the balance between tide-influenced sediment infilling and sediment flushing of the estuary during freshwater flooding events may have shifted toward transporting more sand out of the estuary.
It is anticipated that climate change will have a significant impact on participation in outdoor recreation via changes to weather conditions and modifications to the environments that visitors use. Coastal tourism may be particularly affected by these impacts, as beach visitors are strongly influenced by weather conditions, and sea level rise could have a significant effect on the appearance of coastlines. Despite the importance of coastal tourism to the global economy, the magnitudes of the likely impacts of climate change on beach visits are currently poorly understood. Using a case study of the coastline at East Anglia, U.K., this work models these potential impacts under four future climate change scenarios. Using a Geographical Information System, the output of a model linking visits with beach characteristics and weather conditions is combined with data on likely changes in beach width, temperature, and precipitation to predict future visitor demand. The results suggest that climate change will result in a net increase in visitors on this section of coast, with the positive effects of warmer and drier weather outweighing the negative influences of reductions in beach width due to sea level rise. The findings are discussed in the context of beach management strategies.
The behaviour of sediment fluxes is currently less well understood in the inner-surf and swash zones than farther seaward. In the present study, field measurements were obtained of cross-shore velocity and suspended-sediment concentration from 6 and 13 heights above the bed, respectively, between the breakpoint and the shore of an intermediate-to-reflective beach, over a range of hydrodynamic conditions, to examine the cross-shore structure of sediment flux and the physical mechanisms responsible for the observed patterns. Particular attention is given to the inner-surf and swash zones, which are known to contain sediment-transport processes poorly predicted by models based on velocity moments. The cross-shore structure of the depth-integrated, suspended sediment flux is found to vary according to the forcing conditions considerably more in the inner-surf and swash zones than in the outer surf and shoaling zones. In high-energy conditions, fluxes are dominated by a large offshore peak in the outer swash zone, and in low-energy conditions, fluxes are dominated by weak onshore values increasing shorewards. Examination of the temporal and vertical structure of the velocity, sediment concentration, and flux within individual events where offshore transport was dominant reveals that near-bed suspended sediment responds just as readily to mid-water-column velocity shear as to boundary-layer shear. Examination of events in which onshore transport was dominant reveals that near-bed suspended-sediment concentration responds more readily to near-bed horizontal acceleration than to absolute values of near-bed velocity.
Previous studies carried out in the study area near Port Said, Egypt, concentrated mainly on analyzing the measured and calculated longshore sediment transport data and making predictions by modeling works. Few studies have conducted statistical and uncertainty analyses. In the first stage of this research, wave–time series from altimeter measurements were used for a domain of 50 km in length offshore and 25 km in width alongshore. Wave nearshore transformation analysis was carried out using the SWAN model. The transformed wave data were used for preliminary evaluations of littoral drift. Three formulae were used and were compared with the available target values. As a result, two equations provided suitable correction factors. Applying these corrections, the average values of the evaluations were determined and fit well with the target values.
In this stage of the research, statistical and uncertainty analysis for occurrence probabilities were carefully carried out for these evaluations. The main statistical parameters and the representative occurrence-probability density functions were determined. This investigation showed the importance of concentration on both NNW and NW wave propagation as dominant in the evaluations carried out. The quantity of longshore transport associated with minimum uncertainty in occurrence probability was also determined. The random bootstrap trends for both mean and standard deviation measurements were determined for both summer and winter seasons. Bias trends for longshore transport during the four annual seasons were also determined. The results of these analyses will be beneficial for understanding seasonal changes in littoral drift in this region.
This paper's aims are to investigate the pattern of aeolian sand transport and morphological change in the foredune ridge, Shindu dunefield, Korea. For this purpose, erosion pins and sand traps were installed in three zones, and monitored about once a week over the period of study, December 9, 2000 to approximately March 30, 2001. The results are as follows. First, the main direction of sand transport was onshore irrespective of the monitoring zones, whereas the ratios of parallel transport to perpendicular transport were different according to the monitoring zones and positions. Second, the aeolian activity in the dune base was more active than that in the dune crest, which was due to vegetation cover on the seaside of the foredune ridge. This was reflected by the pattern of morphological change: the focus of volume change in the foredune ridge moved from dune base to dune crest, continuing to bury the vegetation cover. Third, the mean grain size of aeolian sands transported into zone A was coarser than that in zone C. However, no significant difference was observed in all the monitoring zones between aeolian grain size caught in the dune base and that in the dune crest. Finally, the continuous volume increase occurred in the foredune ridge over the period of study. However, the amount of volume change varied according to the zones. Variation in volume change may result from differences in the elevation and orientation of the foredune ridge. The morphological responses of the foredune ridge reveal that the foredune ridge acted as a whole.
The stability and dispersion of dredged material at an offshore disposal site was studied using integrated multibeam–geophysical surveys, sampling, in situ monitoring, and modelling techniques. The disposed material at the disposal site undergoes significant reworking by strong tidal currents and superimposed waves: 84% of the dumped material, mainly fine-grained sediments, was transported away from the disposal site and only 16%, mainly coarser material, remained near the disposal site centre to form an irregularly shaped spoil mound with ∼1 km radius and approximately 14 m height at the disposal centre. A large slump, 1.4 by 1.4 km in size, developed south of the spoil mound because of the failure of the dumped material. Tidal currents up to 60 cm s−1 were measured and can cause sediment mobilization over more than 50% of a tidal cycle. The total-load transport rate calculated using measured currents can reach 0.16 kg m−1 s−1. Superimposition of 1-year storm waves could enhance this by one to two orders of magnitude. Hydrodynamic and sediment transport modeling indicated that the maximum total transport rate for uniform fine sand at the disposal site can reach 0.024 kg m−1 s−1 under tide-only conditions, in the eastward direction during flooding and the westward direction during ebbing. The net transport averaged over a tidal cycle is relatively small (0.00027 to 0.0027 kg m−1 s−1) and to the southeast. The significant enhancement of sediment transport by storm waves clearly indicates that wave effects should be included in assessing the mobility of dredged material at ocean disposal sites. The majority of the disposed sediment was effectively dispersed by the wave-enhanced tidal transport; therefore the disposal site is deemed suitable for continued disposal of dredged material. Future disposals should be spread to a broader area to limit disposal mound build up.
Hurricane Rita generated a 4–5-m-high storm surge along the southwest Louisiana coast. The storm surge and accompanying waves transported sand and mud into woodland and freshwater marsh environments located immediately landward of sandy beaches. The resulting storm surge deposit is up to 0.5 m thick and extends at least 500 m inland. Analysis of the stratigraphy, sedimentology, and microfossil content of the deposit suggests two distinct phases of deposition: a thin layer of finer sand and mud and an overlying thicker layer of coarser sand. The thin layer of finer sand and mud is characterized by planar laminae and calcareous foraminifera, characteristic of shallow marine environments. The layer drapes preexisting surfaces, extends at least 500 m inland, and abruptly overlies woodland and marsh soils. These findings suggest deposition from suspension of offshore sand and mud in an early stage of storm surge inundation. This layer is overlain by up to 0.5 m of coarser sand with prominent foreset laminae. Foraminiferal tests are rare in this part of the deposit. The coarser sand layer has an abrupt termination 100–150 m inland. These findings suggest the sand is a traction load deposit, formed at a later stage of storm surge inundation. The storm surge deposit has a distinctive geologic signature in the study area, raising the possibility of extending paleotempestology studies to this and other similar nearshore environments. The more distal inland part of the deposit has characteristics commonly associated with tsunami-laid sand, suggesting that in studies of coastlines vulnerable to extreme storms and tsunamis, and where the sedimentary evidence is fragmentary, the geologic records of storms and tsunamis may not be easily differentiated.
Many research studies have tried to improve the techniques for effective control of changes in coastal spaces caused by natural or human-induced phenomena. Such alterations modify the capacity for natural regeneration of beaches, and because of the growing population in these areas coastal management must pay close attention to the subject. The method used in this study case at Sauaçui Beach establishes a terrestrial digital model using topographic software fed by a georeferenced data bank generated by a three-dimensional global positioning system (GPS) whose vertical coordinates are referred to as tidal datum. The GPS technology can be used for the accommodation dynamic of the earth's crust of tectonic displacements. This method is able to identify the level curve equivalent to the maximum elevation of the wave run-up line, as well as the position of the waterline, during any stage of tidal elevation through curves of higher or lower levels of elevation, depending on the specific need of the study. Besides determining a baseline for future observations at Sauaçui Beach, this study allows us to evaluate the occurrence of alterations in the volume of sediments at the beach through differences among the generated land surfaces during different periods of time, as well as the risk of substantial variations in the shoreline position caused by eventual sea-level changes.
The Delgado–Lloyd method offers a low-cost alternative for conducting beach profiles that requires only one surveyor. We have revisited the data provided in our original publication and conducted several statistical analyses to properly quantify the accuracy and precision of the Delgado–Lloyd method. Results show a mean precision of 0.014 m and an average accuracy of 0.024 m when compared to theodolite measurements. Individual readings across 2-m sections show high accuracies, which supports the idea that a large part of the error is that any mistake might accumulate along the profile. We analyze the nature of this cumulative error in the context of the Delgado–Lloyd and the Emery methods and reply to some of the arguments of previous discussions. If the instrument used for the Delgado–Lloyd method is properly constructed, individual users with no experience may achieve high levels of accuracy when conducting profiles.
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