Swash zone sediment transport is generally measured in an Eulerian reference frame, but this approach tends to give insufficient information on spatial transport characteristics. This paper utilizes a novel technique to map measured suspended sediment concentrations (SSC) onto the x–t plane, thus providing a visualization of SSC at all locations throughout a swash cycle. The widely adopted energetics or bed shear stress approaches to modeling suspended sediment transport in the swash predict that SSC varies directly with the horizontal velocity, u, to the power of either 2 or 3. A calibrated ballistic swash model was used to predict SSC(x,t) ∝ u² and SSC(x,t) ∝ u³. The qualitative comparison between field measurements and transport model predictions in x–t space provides the opportunity to examine the transport model performance throughout the swash zone. The agreement between observed and modeled SSC patterns was generally poor. Similar to previous observations, SSC was larger during the uprush than the backwash. During the uprush, however, the models predict a maximum in SSC at the moving shoreline and a rapid drop-off behind the leading swash edge, whereas observed SSC was maintained at high levels for most of the uprush phase. During backwash, there was very little correspondence at all between the patterns of predicted and observed SSC; in particular, observed SSC was unexpectedly small in the mid- and late stages of the backwash. A general consensus is emerging that existing swash zone sediment transport models that assume SSC is in equilibrium with the horizontal flow velocity are inadequate. This study suggests that this is probably due to presuspended sediment being advected into the swash zone, the effects of bore-generated turbulence being advected into the swash zone, and both bed shear stress and Reynolds stresses being out of phase with the horizontal flow velocity.

Surrounding the Colorado River Delta is the Sonoran sand sea to the east, delta deposits to the north, and basin and range country plus tidal salt flats to the west. Eolian sands at the western end of the sand sea form a 100-m high escarpment between the Sonoran desert–plateau and the Gulf of California. The western edge of the sand sea has a narrow zone of badland topography with well-developed dendritic drainage patterns. Where the sand sea meets the Gulf of Mexico, eolian sands predominate along the strand. Geometry of the spits indicates a net northward transport of eolian sands into the channel and shoal architecture of the delta. An array of longshore mudflats, salt flats, spits, bars, and coastal dunes dominate the shores of the Gulf.

The USGS EROS data center provided standard images on CD-ROM to order. Browse images and metadata sets are easily accessible via the Internet. Included are the latest Landsat 7 thematic mapper (ETM ) images exploiting the multispectral and panchromatic imagery of this new sensor. The image size of Lansat ∼ 185 × 185 is particularly valuable in study of deltas because most will fit in a single frame. The revisit time interval of 15 d, however, falls way short of what is needed in coastal waters.

This research presents a segmentation-based, image processing method to automate the extraction of tidal datum referenced shorelines from airborne light detection and ranging (LIDAR) data. The method first segments a LIDAR digital elevation model (DEM) into a binary image, consisting of land and water pixels, by intersecting the LIDAR DEM and the tidal datum surface. A chain of image processing algorithms, including region grouping and labeling, two passes of image region scanning, a mathematical morphology operation, line tracing, and vectorization, is sequentially applied to the segmented binary image. Our applications to the upper Texas gulf coast show that the method is efficient, accurate, objective, and replicable. Spatially detailed shorelines can be derived from the LIDAR data with minimal human intervention. The method is a substantial technical improvement over standard cross-shore profile and contouring methods. We also examine and quantify the effects of vertical measurement error of the LIDAR system and the uncertainty in tidal datum determination on the shoreline extraction process using the Monte Carlo simulation technique. The Monte Carlo technique allows confidence intervals and summary error statistics to be calculated for each section of the extracted shoreline. Our analysis suggests that the horizontal position of the MHW shoreline derived from the LIDAR data is accurate within 4.5 m at the 95% confidence level.

The purpose of this paper is to describe the morphodynamics of bars located on an ebb delta of a macrotidal inlet system. Although there have been numerous studies on the morphology and physical processes affecting such bars, these concern only microtidal and mesotidal settings. The west Cotentin coast (Normandy, France) is a fine example of a macrotidal coast with one of the largest tidal ranges in the world. The mean spring tidal range is up to 11 m. Fieldwork was undertaken during one month and involved the deployment of an electromagnetic current meter, a pressure sensor, and differential global positioning system surveys to measure topographic changes. Along the western coast of Cotentin, in spite of the very large tidal inlets, bars are generally small (2 m high and 250 m long) compared with other tidal environments. During the campaign, the bar migrated exclusively landward over a distance of 4 m. Its volume did not change significantly. This slow migration rate is attributed to the large tidal range. In a macrotidal setting, the tidal water level fluctuations control wave height during storms, the duration of emergence and flooding periods, and the intensity and direction of longshore tidal currents. Field observations showed that bar migration rate is correlated with wave activity, whereas volume variations are controlled both by mean tidal currents and wave conditions. These results indicate a morphodynamic behaviour strongly related to specific local macrotidal hydrodynamic conditions, the tidal prism influence being less important.

Physical characteristics such as sand grain size and humidity were determined and the relation between the examined parameters and nesting success, nest density, and hatchling success of green turtles on Samandağ Beach, Hatay, Turkey were investigated in this study. Coarse sand and low humidity at the river site and fine sand and high humidity at distances perpendicular to the river mouth were determined. The wind speed and direction toward land on the beach are important factors forming grain structure on Samandağ Beach. The mean particle size, about 350 μm, at nesting locations (N) of green turtles is smaller than that at nonnesting areas (NT and T). Nesting sites have the lowest uniformity coefficients (C_u = 2.78) on the surface than in no-nest no-track sites (C_u = 3.48) and in only-track sites (C_u = 3.5) on the surface. A negative correlation exists between sand moisture and nesting success with respect to increasing distance from Çevlik Harbor for Chelonia mydas. The hatchling success of C. mydas was found to be significantly affected by sand moisture. When sand moisture is above 8%, hatchling success become too low or no successful hatching occurs.

The suspension and enrichment of heavy sands at Chavara, southwest coast of India, were examined by studying the beach and nearshore sedimentology, mineralogy, fall velocity patterns, bed reference concentrations, and mixing length characteristics. The outer shelf is carpeted with sand mixed with silty-clay sediments. On the inner shelf, the coarse fraction of the heavy sands increases near the coast, whereas the finer fraction spreads more evenly right across the shelf, to both the south and north of Chavara. The beach is composed mainly of medium to fine sand. Seasonally, beach sediments are poorly sorted during the postmonsoon, and settling velocity measurements indicated that sediment grain size was coarser at this time than during the monsoon period. Further, the beach face becomes enriched with heavy sands, with a corresponding loss of quartz sands, during erosive monsoonal events. A bimodal coarse population of mixed colour of black and white arrived at the beach after the monsoon. Although sediment trap data exhibited maximum sedimentation during the monsoon, sediments on the inner shelf out to an 8-m depth were highly mobile because of waves and currents throughout the year. A log-linear concentration profile was found with the sediment traps, and the grain fall velocities decreased with elevation. The evidence suggests that the postmonsoon coarse fraction comes from the inner shelf, with denser minerals near the bed moved most effectively toward shore. This may occur because of wave asymmetry causing shoreward near-bed sediment migration of the denser sands during the clean swells of the post monsoon. The finer sands, which penetrate higher in the water column, are not subject to bedload asymmetrical transport and so they are relatively absent from the beach when the heavier sands start arriving in the postmonsoon.

The coastal zone is under considerable pressure from development and is subject to change. Consequently, shoreline monitoring has grown in importance. Remotely sensed imagery from satellite sensors has been used as an alternative to conventional methods, such as those based on the interpretation of aerial photography and ground-based surveying, for monitoring shoreline position. However, the accuracy of shoreline mapping from satellite sensor imagery has been limited because of the relatively coarse spatial resolution (>10 m) of the sensors commonly used. Because of major practical and financial constraints, very fine spatial resolution (<5 m) data are often impractical for mapping large stretches of shoreline, so refinement of image analysis methods are needed to extract the desired subpixel-scale information from relatively coarse spatial resolution imagery. In this paper, the potential to map the shoreline at a subpixel scale from a soft classification of relatively coarse spatial resolution satellite sensor imagery was evaluated. Unlike conventional approaches, the methods used allowed the shoreline to be mapped within image pixels and have the potential to yield an accurate and realistic prediction of shoreline location. The approach involved the use of a soft image classification to estimate the subpixel-scale thematic composition of image pixels, which were then located geographically through postclassification analysis. Specifically, a contouring and geostatistical method based on a two-point histogram was used to position geographically the shoreline within image pixels. The approach was applied to differently shaped shoreline extracts in imagery at two spatial resolutions. The most accurate prediction of the shoreline position from images with 16- and 32-m spatial resolutions were typically for a simple linear stretch of coast for which the smallest root mean square error values were ≤1.20 m. The shoreline predictions satisfied the map accuracy standards specified for large-scale maps.

Sediment deposition along the coasts of French Guiana depends on three different processes: mass deposition when a mudbank reaches the area, seasonal exchange between the mudbank and the shoreline, and the effect of tide cycles. The objectives of this work were to determine whether the three different processes are recorded in the sediments, and if rhythmites are discernible, preserved, and usable for paleoenvironmental studies.

The study area was in the Kaw estuary, southeast of Cayenne (French Guiana) at a latitude of about 4°55′N and longitude about 5°10′W. Four stations were selected for the collection of push cores, which were then split and described. Redox and water content were measured; grain-size analyses, radioisotopic measurements (²¹⁰Pb geochronology), and X-ray image-analyses were carried out. The SCOPIX X-ray image-processing tool was used for establishing gray-scale profiles.

After mass deposition, sediment processes are dominated by reworking of the muddy sediment with a predominance of tidal effects. Erosion and deposition processes are governed by tide cycles and depend on threshold speeds of tidal currents. Microphytobenthos, mainly diatoms, play a major role in binding the sediment by secretion of extracellular polymeric substances (EPS). They induce the formation of alternating dark and clear laminae. Even if erosion, irregular seasonal sediment supply, and bioturbation do not allow continuous recording of sediment laminae, the cyclic sediment deposits may result in tidal rhythmites, even in the highly size-sorted sediments of French Guiana. When preserved, the rhythmites provide valuable information on fortnightly cycles.

An annular flume (Lab Carousel) was used to investigate the influence of shells on the erosion rates of an artificial laboratory cohesive bed (potters clay) under unidirectional flow. Specimens of articulated and disarticulated cockle shells (Cerastoderma edule), separated into six size classes (of maximum diameter from 13 to 26 mm), were used. The fluid-transmitted shear stresses and shell-induced bed erosion for the six classes were measured in triplicate, as well as shell settling velocity, sedimentation diameter, and shell drag coefficient. Bed erosion began after the shells started to move: erosion rates were influenced by shell size and the mode of transport. Two different modes of shell transport were observed: (i) rolling and saltation of articulated shells, and (ii) sliding and saltation of disarticulated shells. Peak bed erosion rates were associated with rolling and sliding modes of transport. Higher values of the solid-transmitted shear stress were calculated for saltating shells (in some cases two times higher), but contact with the bed was less frequent than rolling or sliding. The presence of cockle shells in an environment with hydrodynamic conditions strong enough to induce shell transport could significantly increase the loss of mass (erosion) of the surface bed or cliff. At Hythe intertidal area, where the shell specimens were collected, the presence of miniature furrows containing shells deposits in the troughs is widespread, and the troughs and walls show tool marks indicating shell abrasion.

Nutrient levels in coastal waters are significantly enhanced through atmospheric deposition. Bulk atmospheric deposition was sampled at 10 different sites throughout the Charleston Harbor watershed. Fluoride, chloride, phosphate, nitrate, and sulfate concentrations in the samples were determined with ion chromatography. Sulfate concentrations showed no statistically significant spatial variability. However, chloride and fluoride concentrations are found to be higher in samples from oceanside sites vs. the inland sites, presumably because of higher concentrations of sea spray aerosols. Samples from inland sites had higher concentrations of nitrates, presumably because of stronger influences of anthropogenic sources and continental dust aerosols. Samples from urban oceanside sites had higher fluoride, chloride, and nitrate concentrations than did samples from rural oceanside sites, suggesting an anthropogenic influence. Higher chloride and nitrate concentrations were noted in samples associated with Hurricane Opal.

The method of labeled natural sand particles was used to study sediment transport along the central Mediterranean coast of Israel. Six portions of 300 kg each were tagged with various fluorescent colors, and distributed at six different locations in the vicinity of the Herzliya Marina. The tagged sand was scattered at the end of autumn, and sampled three times during the winter. Sampling was interrupted in mid-January because of unexpected dredging at the marina canal entrance.

The samples were analyzed at the Yigal Allon Kinneret Limnological Laboratory. The wave climate during that time was analyzed using wave data from Ashdod (40 km south). Wave directions measured in Ashdod were corrected to make them applicable to the Herzliya coast, in accordance with suggested directional shift values.

Seven wave storms with significant wave heights of over 2.5 m were observed. Two of them clearly indicate a dominant direction from the southwest and two others from the northwest. However, the time durations and the relative angles between the wave directions and the orthogonal to the coast of the storms propagating from the southwest are essentially larger than those arriving from the northwest.

The following results were noted: (i) The drift of tagged sand particles correlated to longshore sediment transport at all depths was in a northern direction throughout the field experiment. The longest distance of transport was 5 km over a period of 36 days. (ii) “Onshore” sediment transport was present; sand from 15 m depth was found at 8 m depth. (iii) The cross-shore sediment transport carried sand to a depth of 8 m, but no colored sand from shallow water (2–4 m) was found deeper than 8 m. (iv) Although sedimentation at the marina entrance during the experiment was high, only small amounts of tagged sand were found at the entrance. (v) Findings of tagged sand showed the main area of sedimentation to be along the marina's main breakwater.

The monitoring of existing coastal protection work and comparing the actual performance with the predicted one is one of the methods for developing coastal engineering processes. A comprehensible example, which clearly demonstrates the value of this monitoring process, could be found in the coastal protection works of El Agami resort area, Egypt. A group of seven detached breakwaters were constructed in front of the study area aiming to improve the beach condition with consideration for swimming capability. This is in addition to a temporary harbor to facilitate execution of the breakwaters. Deposition of seagrass and an undesirable temporary harbor are part of the coastal area problems.

The implicit sediment transport two-dimension (ImSedTran-2D) numerical model, prototype data during the period from October 2002 to October 2003, and the empirical design relationships were used to study the environmental impact assessment of the breakwaters. Accordingly, a decision was made to eliminate the temporary harbor.

The study area was observed to be quite stable, even with the detached breakwaters. This could be attributed to the orientation of the shoreline and its offshore submerged ridge, which extends parallel to the shoreline. Removing the harbor improves the ecosystem of the zone just behind the western breakwater by clearing out and stopping the deposition of the seagrass in this area with its negative effect on beach condition. The study area can be considered an ideal case because the empirical relationships, the prototype data, and the numerical model give more or less the same results.

The coastal zone is a dynamic area in which processes with different origins and scales interact. Several techniques can be used for coastal zone monitoring. Remote sensing is a powerful tool for monitoring coastal processes and managing coastal areas. The quality of coastal water is a very important issue, and remote sensing optical sensors can be used to quantify water quality parameters such as suspended sediments. Therefore, it is possible to estimate the total suspended matter (TSM) concentration with multispectral satellite images. To extract meaningful information, the satellite data need to be validated with in situ measurements. The main objective of this work was to quantify TSM concentrations in the breaking zone with in situ measurements. In situ validation is important for the accuracy of correlations established. A section of the northwest coast of Portugal, near Aveiro city, was chosen as a test area, and all in situ measurements were done in this area. Several in situ techniques have been used to establish a relationship between seawater reflectance and TSM concentration for the range of wavelengths from 400 to 900 nm. Empirical relationships were established for equivalent reflectance values by SPOT/HRVIR (high-resolution visible infrared), Terra/ASTER (advanced spaceborne thermal emission and reflection radiometer), and Landsat TM (thematic mapper) at visible and near-infrared equivalent bands and TSM concentrations. The reflectance values were used to estimate TSM concentration with the use of the relationships established by in situ measurement.

The reflectance of all bands of the satellite images tested showed high correlation with TSM in the wavelengths between 500 and 900 nm. The water leaving equivalent reflectance for each sensor equivalent band in the visible and near-infrared wavelengths was calculated, and a relationship between seawater reflectance and TSM concentration was established. The model coefficients and correlation factors for identical bands on different sensors presented good similarity. The work presented shows that TSM concentration in the breaking zone can be obtained directly from simulated multispectral satellite data. However, in situ measurements are essential to calibrate the process and establish the empirical relationships between TSM concentration and water leaving reflectance.

The same empirical relationships found with in situ measurements will be used to estimate the TSM concentrations directly from real satellite data to try to quantify the sedimentary balance in the study area for the period of the satellite data.

The coastal zone of Sagar Island, India, is subjected to various cyclic and random processes that continuously modify the region. The shoreline and land-use/land cover changes have been studied using Indian Remote Sensing Satellite 1C (IRS IC) linear imaging self-scan sensor (LISS) III satellite data from 1998 and 1999. A comparison between a topomap of 1967 and satellite data of 1999 established that during these years about 29.8 km of coastline was eroded, whereas the accretion is only 6.03 km². A comparison of satellite data from 1998 and 1999 showed that the island had undergone severe erosion of about 3.26 km², while the accretion was just about 0.08 km². Change detection studies based on land-use patterns of the region revealed that the areal extent of mangrove vegetation of the island during 1998 and 1999 was 2.1 km² and 1.3 km², respectively. The areal extent of agricultural fields during these periods was 130.4 km² and 118.6 km², respectively. These results can be used to develop an index for temporal land-use changes in the region as an aid to quantify the extent and nature of the development change and to understand the surrounding environment, which in turn may help the planning agencies to develop sound and sustainable land-use practices.

Coastal stands of Taxodium distichum L. Richard (baldcypress) in Louisiana, USA, are in decline because of saltwater intrusion, prolonged flooding, and periodic defoliation by an insect herbivore, Archips goyerana Kruse (Lepidoptera: Tortricidae; the baldcypress leafroller). The objective of this study was to examine the potential for the use of variation in budbreak among half-sibling families previously evaluated for salt tolerance as a means of resistance to defoliation. Four half-sibling families were categorized as either early (FA7, SG2) or late (SW2, VE2) leafing during budbreak. Laboratory bioassays in 2002 found that larvae fed on foliage collected on the same date encountered foliage from early-leafing half-sibling families of an advanced age that was significantly lower in N, P, K, and moisture content and significantly higher in digestion-inhibiting compounds (phenolics) than foliage from later leafing half-sibling families. Insect pupal weights and relative growth rates were significantly lower on early-leafing half-sibling families. In 2003, the early and late-leafing families were experimentally synchronized with larvae by collecting foliage from family groups in order of budbreak. Foliar N remained significantly higher and total phenolics significantly lower in the late-leafing families; however, moisture content, P, K, and insect pupal weights and relative growth rates did not differ significantly between early- and late-leafing half-sibling families. Intraspecific budbreak variation in baldcypress can affect insect growth and, potentially, baldcypress leafroller populations and should be explored further. The success of coastal baldcypress restoration programs in Louisiana might be improved by capitalizing on separate traits that reduce damage from herbivory and salinity.

In French Guiana, the constant migration of large mud banks resulting from the Amazon River's sedimentary discharge has a negative impact on the local economy. Two radar images from the new ASAR/Envisat sensor have been analysed and compared to one ASTER image to assess their potential for mud bank monitoring. Bathymetric data were also recorded at times close to those of the satellite acquisitions, enabling a comparative study of the mud bank morphology and bathymetry and satellite information.

The emerged parts of the mud banks, whether consolidated/solid (slikke or mudflats, mud bars, etc.) or fluid mud are easily detectable on the ASAR images. However, the results show that mud bank covered by a shallow layer of water (a few tens of centimetres) is not detectable on ASAR images. For deeper waters the ASAR signal is independent of water depth. ASAR's multipolarized images provide little more information than that obtained from older sensors having only a single polarization (ERS-1/2 and RADARSAT-1). The Horizontal transmit and Horizontal receive (HH) and Vertical transmit and Vertical receive (VV) polarizations have equivalent cartographic potentials, markedly superior to that provided by the VH polarization. However, the VH brings out certain information that is hard or impossible to see in HH or VV, for example, some offshore emerged portions of the banks, and provides a better separation between water and coastal mangrove forest. The ASTER image enables effective mapping of the extent of emerged mud banks and identification of three classes of water depth.

Over the centuries, London has progressively encroached into the tidal Thames River as it has developed into a “World City”. This encroachment has exacerbated the flood risk to new and adjacent land, despite continual upgrading of flood defences. The pressure for further encroachment remains, despite the new threat of human-induced climate change—that is, the combined effect of (1) increased peak river flow in the winter, (2) more intense precipitation events, (3) accelerated sea-level rise, and possibly (4) more severe storms and resulting storm surges. Costly upgrade of defences is inevitable to manage the increased flood risk, and this has caused a re-evaluation of the Thames Estuary's flood defence program. For the first time, managed realignment in urban areas is being considered as a flood management tool. This offers a range of potential benefits including (1) increasing storage for floodwater, (2) improving ecological functioning, (3) improving riverside access for people, and (4) reversing the long-term trend of encroachment into the river. Planned managed realignment can widen the scope for future defence upgrade, but has been limited in urbanised areas. Several projects in London (e.g., Tate Modern and Millennium Dome) have shown that realignment can achieve the benefits described above, which supports the government's recent “Making Space for Water” policy.

This study investigates the feasibility of managed realignment in the Thames Estuary. Fragmentation between flood defence and spatial development policies, lack of political support, and riverside encroachment continue to delay urban realignment projects. Successful application will require long-term planning (over decades) that exploits all opportunities for landward realignment offered by redevelopment. With the uncertainties behind climate change and more development in the “Thames Gateway”, further research is needed to understand the contribution of urban realignment to any flood management strategy that may be applied to other coastal urban areas.

Five lithofacies were identified in beachrock ledges distributed along the eastern and northern coasts of the state of Rio Grande do Norte, northeastern Brazil: (1) massive to weakly stratified conglomerate, (2) low-angle cross-stratified conglomerate and sandstone, (3) medium-scale tabular-planar and trough cross-stratified sandstone, (4) Skolithos-bioturbated conglomeratic sandstone, and (5) massive sandstones. Most of the described beachrocks (53% relative to total thickness) were deposited on the upper shoreface zone, represented by lithofacies 3 and 4. Lithofacies 2, which was deposited on the foreshore zone, represents 31% of the sections described. The remaining 16% are attributed to collapse of overlying material as a result of sea cliff undercutting (massive conglomerate, lithofacies 1), transport as a traction carpet deposit (weakly stratified conglomerate, lithofacies 1), and a high degree of alteration (lithofacies 5). The distribution of ¹⁴C-dated beachrock samples in a sea level envelope curve shows that, along the northern coast, framework constituents were predominantly deposited between approximately 4140 and 2190 cal. yr. BP, when sea level dropped, and during low sea level stillstand. On the northern coast, the upper shoreface sedimentation zone is preferentially distributed during sea level drop and low sea level stillstand phases, whereas the foreshore sedimentation zone can be found along the whole sea level curve. Conversely, the beach deposits distributed along the eastern coast were preferentially formed between approximately 7460 and 4240 cal. yr. BP during rapid sea level rise and high sea level stillstand. In the case of the eastern coast, both zones are equally concentrated in the first stages of rapid sea level rise and high sea level stillstand.

This paper describes a research project that has been conducted as part of the coastal habitat and management plans initiative (ChaMPs). The primary aim at this stage is to identify and quantify the salt marsh decline by mapping the changing extent of salt marsh coverage during the last 30 years.

Rectified aerial images of the salt marsh were created for three epochs. The salt marsh and coastal boundaries were then mapped using a head-up digitising technique combined with stereo aerial photo interpretation. This methodology, though simple, provides an important estimate of salt marsh change for a number of harbours and estuaries in southern England.

The results show a rapid decline in salt marsh habitat, with some areas showing a reduction of over half their existing salt marsh between 1971 to 2001. The authors consider the various theories that have been presented to account for this dramatic change and offer preliminary explanations. Though no doubt resulting from the combined effects of rising sea levels, Spartina dieback, restricted sediment supplies, pollution, and coastal squeeze, the authors underline the need for more detailed case studies of specific sites in the future.

In this paper, we focus on a complex management issue, namely the physical effects of a large-scale offshore sand extraction. For these kinds of issues there is no obvious morphological model available to answer all management questions. Therefore, we aim to answer as many management questions as possible, using a set of existing morphological models parallel to each other. In this way, we can support governments to assess applications for licenses for large-scale sand extraction. We investigate whether this parallel modeling approach is significantly more helpful in addressing the management questions than a single modeling approach. The management questions are translated into quantifiable variables, known as Coastal State Indicators (CSIs). We focus on three coastal user functions: coastal safety and maintenance, offshore infrastructure, and navigation. The selected morphological models are assessed on (1) their applicability to the CSIs and (2) the reliability of their predictions. We quantify the predictive power of the models based on these two parameters. We conclude that by using a parallel modeling approach it is possible to address more management questions effectively in comparison with using just the best single model. The use of this parallel modeling approach increases the predictive power significantly, here 35%.

Floating freshwater marsh communities (flotant) in the Mississippi Deltaic Plain are composed of vegetation rooted in an organic mat that detaches from the underlying mineral substrate and shifts vertically as water levels below rise and drop. Unlike attached marshes dominated by herbaceous species, floating marsh mats are free from the stress of inundation, enabling establishment of woody species. Dynamics of these flotant communities are largely unstudied, and it is unknown whether invasion by woody species alters their structure and composition. To study the potential effects of woody species invasion on herbaceous community characteristics, we compared open herbaceous marsh, sparse scrub-shrub, and dense scrub-shrub thickets at Jean Lafitte National Historical Park and Preserve in coastal Louisiana. We found that species richness and composition differed significantly among the three marsh types. Herbaceous communities lacking shrub canopies had the lowest richness and were dominated by emergent species typical of freshwater marsh. Richness and composition of sparse scrub-shrub thickets were intermediate between open marsh and dense thickets. The latter had the greatest species richness with assemblages more typical of forest understories, as well as aquatic species that occurred where holes in the floating mat formed. Morella cerifera (wax myrtle), an actinorhizal shrub, was the dominant woody species and formed the shrub stratum in sparse and dense thickets; the exotic Triadica sebifera created a low-stature overstory. Bryophytes colonized the bases and lower stems of both species. We found 35 additional vascular plant species in the thickets, including two other exotics, Alternanthera philoxeroides and Salvinia molesta. Establishment of woody species in flotant marsh adds structural complexity and appears to drive compositional changes in the herbaceous community toward a combination of woodland and aquatic assemblages. The longevity of the woody phase in flotant marsh and the long-term ecological consequences of widespread Triadica sebifera invasion are unknown.

Modified Newton–Raphson solution for dispersion equation of transition water waves is proposed for practical applications. The wave dispersion equation is a nonlinear equation. Therefore, one has to apply a time-consuming trial-and-error method. However, it may be solved by utilizing an iterative technique commonly referred to as Newton–Raphson (NR) iteration technique and Chebyshev approximation, which are used to solve the system of nonlinear equations. Chebyshev approximation has the advantage of requiring less iteration. In this study, a numerical solution model based on utilizing modified NR technique with Chebyshev approximation to determine value of the wave number (k) is developed. It is shown how iteration problems can be solved by modified NR technique with Chebyshev approximation. This computational model is applied by computer programs that have visual basic (VBA) code prepared under the Microsoft Excel Macro. The wave dispersion equation for transition water waves were solved by modified NR technique with Chebyshev approximation implemented in the computer programs prepared with VBA computer language. An example for the given numerical solution model is presented.

This study investigates the nonlinear wind–wave interaction that occurs during wave growth. Wavelet bicoherence is used in analyzing the detailed phase coupling and nonlinear interaction between wind speed and wave height considering both the sum and difference rules between different frequencies to give the full picture of nonlinear wind–wave interaction.

The results show that the phase coupling and nonlinear wind–wave interaction in the case of considering the sum rule of the frequencies is different from the case of considering the difference rule of frequencies. This consequently emphasizes the importance of considering both rules in analyzing the phase coupling between wind speed and wave height during wave growth.

Dauphin island is a microtidal barrier island located approximately 8.0 km offshore from southwestern Alabama (U.S.A.). Morphological changes to the island, brought about by passing tropical storms and hurricanes, have been noted since it was first settled in 1699. On August 29, 2005, Hurricane Katrina (a Category 3 hurricane) made landfall approximately 117 km west of Dauphin Island. Despite the extended distance, the storm impacted the island with waves that completely overwashed and flattened most of the western low-lying areas. The hurricane also segmented Dauphin Island into two distinct barrier islands, the undeveloped Dauphin Island West, and the residentially developed Dauphin Island East. Immediately following the storm, the Town of Dauphin Island recognized the need to take action to protect low-lying residential property on the western segment of Dauphin Island East. Sand berm construction began on January 29, 2007. The 6.4-km-long berm is to provide sufficient time to allow the Town of Dauphin Island to identify and possibly implement a more permanent solution to storm erosion along the low-lying western residential portion of the island before the sand wall will be lost. However, the western end of the sand berm experienced significant erosion due to elevated tides before construction was completed in May 2007. Several segments of the sand berm within this area have been completely lost while other sections are experiencing ongoing erosion. Under these conditions, the Town of Dauphin Island does not have much time to identify and implement one or more long-term solutions to beach erosion and property loss for the western segment of Dauphin Island East.