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The coastline of Hai Hau District, located on the northeast coast of Vietnam with about 30 km of shoreline, is chronically eroding. Previous studies have tried to highlight the main causes of the erosion along this coastline, and several hypotheses exist. To examine the hypothesis that gradients in the longshore sediment transport rate and cross-shore fine sediment lost offshore are the main causes generating the serius erosion at Hai Hau Beach, a newly developed numerical model of shoreline change based on the one-line theory was applied and compared with data. Sea dike segments, reinforced by stones and mortar, were modeled using a seawall boundary condition, and the sediment continuity equation was modified to take into account the offshore transport of fine-grained sediment. The simulated shorelines agreed well with the measured shorelines, both for the calibration and validation periods. The calculated sediment budget shows that the net sediment transport is in the southward direction and that a large amount of finegrained sediment is lost into deep water. These two sinks of sediment are believed to be the main causes of the serious erosion at Hai Hau Beach. [ABSTRACT FROM AUTHOR]

The geomorphology and processes of land loss in the Pontchartrain Basin for the period 1990-2001 are mapped and the results of the classification presented. This data set is compared to an earlier classification, which covered the period 1932-1990 to determine the status and trends of wetland loss in the Pontchartrain Basin between 1932 and 2001. Results of the land loss classification indicate land loss rates have remained steady between the two periods (13 km2/y between 1932 and 1990 and 12 km2/y between 1990 and 2001). The geomorphology and processes of loss have shifted from primarily interior loss as a result of direct removal and submergence in the first period to primarily shoreline loss as a result of erosion in the second period. Three areas of concentrated land loss between 1990 and 2001 represent portions of the upper, middle, and lower basin. Land loss at all three locations shifts from interior to shoreline loss between the two periods. In the second period, interior loss through the process of submergence is still occurring but at much reduced rates at locations 1 and 2. Interior loss through the process of direct removal is only occurring at location 1 during the second period and accounts for less that 2% of the loss. At location 3, land loss is completely in the form of shoreline erosion during the second period. [ABSTRACT FROM AUTHOR]

A generalized methodology, relevant for a wide variety of shoreline change analyses, is developed to estimate the horizontal offset between proxy-based high water line (HWL) type shorelines and datum-based mean high water (MHW) type shorelines. The ability to compute this term is critical for change analyses that incorporate variously defined and derived shoreline estimates because this horizontal offset nearly always acts in one direction; HWL shorelines are landward of MHW shorelines. Not accounting for this offset will cause shoreline change rates to be biased toward slower shoreline retreat, progradation rather than retreat, or faster progradation than in reality (for the typical case where datum-based shorelines are collected after proxy-based shorelines), depending on actual changes at a given site. It is also demonstrated that by computing the uncertainty associated with this proxy datum shoreline bias, we are quantifying, for the first time, the uncertainty of HWL shorelines due to water level fluctuations. Complete accounting of the uncertainty of shoreline position estimates is necessary for determining the statistical significance of shoreline change rate computations. The proxy-datum bias and the bias uncertainty are estimated to be approximately 18 and 9 m, respectively, on average for the sandy beaches of the California coast (and significantly larger on the milder sloping beaches of the U.S. Pacific Northwest). The importance of accounting for the bias in calculating shoreline change rates is confirmed as its inclusion along the California coast changes the coastwide decadal-scale (1970s to present) shoreline change rate from net progradation to net shoreline retreat. [ABSTRACT FROM AUTHOR]

The indentation index, which is the ratio between the real length of a coast and its Euclidean length, is a parameter applied to characterize rock coasts and to study their evolution. Rather than subjectively selecting two or more sectors of a rock coast, the method proposed in this paper considers analyzing the indentation index on the same coastline previously split into several adjacent tracts with equal Euclidean length. By digitizing the coastline in a GIS environment, it becomes possible to test several Euclidean length values on the same coastline, obtaining a different spatial variability of the indentation index with each trial. The best length values that maximize the spatial variability of the indentation index are those that determine an indentation index pattern characterized by high variance and low spatial autocorrelation. The spatial distribution of the indentation index can eventually be analyzed considering known littoral forces acting on the studied coast. When more than one Euclidean length value is found to maximize the variability of indentation index within the same coast, it is likely that there are one or more littoral forces acting or interacting differently at different scales. [ABSTRACT FROM AUTHOR]

A ground-penetrating radar survey of a newly formed series of beach ridges along the southern Azerbaijan coast, Caspian Sea, illustrates rapid coastal response to the most recent sea level fall of 0.8 m in the Caspian Sea between 1995 and 1999. Effects of seasonal sea level fluctuations as well as individual storm occurrences can be linked to depositional beds on the ground-penetrating radar profiles. The beach ridge system is swash built and formed primarily under fair weather conditions. Ridge and swale topography can be related to seasonal sea level change. The rapid sea level change in the Caspian Sea combined with surface and subsurface data on coastal beach ridges provides a unique opportunity to observe and reconstruct coastal evolution at a resolution not possible along other oceanic coasts. [ABSTRACT FROM AUTHOR]

Beach erosion has direct consequences for Hawaii's tourist-based economy, which depends on the attraction of beautiful sandy beaches. Within the last century, however, beaches on Oahu and Maui have been narrowed or completely lost, threatening tourism and construction development. In order for the counties and state of Hawaii to implement coastal regulations to prevent infrastructure damage, it is necessary to find a statistically valid methodology that accurately delineates annual erosion hazard rates specific to Hawaii. We compare the following erosion rate methods: end point rate (EPR), average of rates (AOR), minimum description length (MDL), jackknifing (JK), ordinary least squares (OLS), reweighted least squares (RLS), weighted least squares (WLS), reweighted weighted least squares (RWLS), least absolute deviation (LAD), and weighted least absolute deviation (WLAD). To evaluate these statistical methods, this study determines the predictive accuracy of various calculated erosion rates, including the effects of a priori knowledge of storms, using (1) temporally truncated data to forecast and hindcast known shorelines and (2) synthetic beach time series that contain noise. This study also introduces binning of adjacent transects to identify segments of a beach that have erosion rates that are indistinguishable. If major uncertainties of the shoreline methodology and storm shorelines are known, WLS, RWLS, and WLAD better reflect the data; if storm shorelines are not known, RWLS and WLAD are preferred. If both uncertainties and storm shorelines are not known, RLS and LAD are preferred; if storm shorelines are known, OLS, RLS, JK, and LAD are recommended. MDL and AOR produce the most variable results. Hindcasting results show that early twentieth century topographic surveys are valuable in change rate analyses. Binning adjacent transects improves the signal-to-noise ratio by increasing the number of data points. [ABSTRACT FROM AUTHOR]

Few observational techniques are capable of simultaneously mapping the shoreline and nearshore sand bars at high resolution and over large distances, especially during storms when waves are large and visibility is reduced. Proof-of-concept experiments were undertaken to test the feasibility of using X-band radar, mounted on a beach vehicle with dual-channel global positioning system (GPS), to rapidly map the swash and nearshore bars over several kilometers. Bar and Swash Imaging Radar (BASIR), a mobile system developed in collaboration with Imaging Science Research, was evaluated under varying wave heights and storm conditions through comparisons with bathymetric profiles and video along the North Carolina Outer Banks. The video, operated by Oregon State University Coastal Imaging Lab and the U.S. Army Corps of Engineers Field Research Facility in Duck, North Carolina, utilizes a similar technique of time averaging and multiple-image merging to map sand bars. Significant correlation and relatively low root-mean-square differences were found between the video and radar mosaics. Bar and swash imaging radar under-predicted the cross-shore distance of the inner bar relative to measured bathymetric profiles. Measurements collected during a storm with significant wave heights of 3.5 m compared very closely with the results collected 12 hours later when seas had fallen to 2 m. Results suggest BASIR may prove to be a robust observational technique for mapping the evolution of swash-defined shorelines and nearshore bars during storms. At present, limitations to BASIR include (1) alongshore mapping distance constrained by tide fluctuations and (2) the necessity of having wave heights substantial enough to dissipate over the mapped feature. [ABSTRACT FROM AUTHOR]

In this paper, results obtained from an experimental investigation conducted to determine wave-induced geometric characteristics of shorelines protected by partial revetment structure are presented. The experiments were performed with both regular and irregular waves. The beach sand used in this study had a mean diameter of 0.35 millimeter and a specific gravity of 2.63. The beach had an initial slope of 1 : 5 and was protected by the partial revetment structure. For this purpose, the armor units, mean diameters and specific gravities of which were varied in the range 8.5–67.95 millimeters and 1.81–2.77, respectively, were placed on the wave-breaking area. Different wave groups were generated over an initially fiat, partially protected beach, and a number of geometric characteristics of equilibrium beach profiles was determined. Moreover, the static damage of the armor layer was obtained for all test groups. The results of this experimental study were evaluated, and empirical expressions based on the results were formulated to define geometric parameters of equilibrium profile under pure regular waves, pure irregular waves, and regular- irregular waves. The findings showed that the partial revetment structure decreases shore erosion on average 65–70%. Because the sand of the unprotected area spreads over the armor layer, this revetment type does not disturb the beauty of the area and its aesthetics. Moreover, it is a low-cost structure, because the armor layer was placed only within the wave-breaking area, not across the entire slope. [ABSTRACT FROM AUTHOR]

More than one type of shoreline indicator can be used in shoreline change analyses, and quantifying the effects of this practice on the resulting shoreline change rates is important. Comparison of three high water line (proxy-based) shorelines and a mean high water intercept (datum-based) shoreline collected from simultaneous aerial photographic and lidar surveys of a relatively steep reflective beach (tan β = 0.07), which experiences a moderately energetic wave climate (annual average H8 = 1.2 m), reveals an average horizontal offset of 18.8 m between the two types of shoreline indicators. Vertical offsets are also substantial and are correlated with foreshore beach slope and corresponding variations in wave runup. Incorporating the average horizontal offset into both a short-term, endpoint shoreline change analysis and a long-term, linear regression analysis causes rates to be shifted an average of -0.5 m/y and -0.1 my, respectively. The rate shift increases with increasing horizontal offset and decreasing measurement intervals and, depending on the rapidity of shoreline change rates, is responsible for varying degrees of analysis error. Our results demonstrate that under many circumstances, the error attributable to proxy-datum offsets is small relative to shore- line change rates and thus not important. Furthermore, we find that when the error associated with proxy-datum offsets is large enough to be important, the shoreline change rates themselves are not likely to be significant. A total water level model reveals that the high water line digitized by three independent coastal labs for this study was generated by a combination of large waves and a high tide several days before the collection of aerial photography. This illustrates the complexity of the high water line as a shoreline indicator and calls into question traditional definitions, which consider the high water line a wetted bound or "marks left by the previous high tide." [ABSTRACT FROM AUTHOR]

Rapid shoreline changes at Stromboli Island have been documented from maps and aerial photographs dating from 1938 to 2003. Shorelines digitized from aerial photographs, taken at decadal intervals on average, show that while cuffed tracts were relatively stable, beaches on the N and NE side of the island experienced alternating accretion and erosional stages linked, respectively, with the contemporary eruptions and with sediment redistribution and/or the washing out and loss of sediment to deeper waters. Sciara del Fuoco, on the central-western side of the island, is where most of the volcanic products have accumulated during the practically continuous activity of the last two thousands years; from there, sands and gravel drift alongshore and are added to beaches on the N and NE side of the island. A simple model of clockwise longshore drift along the W, N, and NE coasts of the island is presented, taking into account the influences of manmade structures on shoreline changes. [ABSTRACT FROM AUTHOR]

The bones and teeth of vertebrates occur on shorelines in quantities sufficient to provide a guide to the range of animals that live both inland and offshore. Burial is necessary for any remains to enter the fossil record and coastal deposits representing intertidal and shallow subtidal environments are potential repositories of this record. A survey of 150 published reports on rocky shores from the Cambrian to the Pleistocene reveals approximately 5% in which vertebrate remains are listed and described. In all cases, the vertebrates involved are marine in habit, but there is no reason to suppose that the remains of land-dwelling vertebrates should be excluded from such deposits. The potential for dinosaur remains to be incorporated in marine coastal deposits is appraised with particular attention to the Upper Cretaceous of Baja California (México) and southern California (U.S.A.). Newly discovered hadrosaur (duckbill) dinosaur bones from the Eréndira area on the Pacific coast of Baja California (México) are described as related to a Late Cretaceous rocky shoreline. [ABSTRACT FROM AUTHOR]

Dredged materials from maintenance and deepening of inlets on coastal barriers are typically transported for disposal in deep water or on land. An alternative is to treat dredged materials as a resource, placing them on the ebb-tidal delta or subtidal shoals at depths where they are retained within the long-shore transport system and can nourish eroding down-drift beaches. Deposition of sediments onto subtidal shoals may, however, bury and selectively kill populations of benthic invertebrates, or indirectly alter assemblages by modifying sediment characteristics. Core sampling of the eastern (control) and western (disturbed) sides of Beaufort Inlet, North Carolina, twice before and once 8 months after a large (660,000 m³) disposal revealed significant coarsening of sediments and associated changes to assemblages of benthic macroinvertebrates in response to the perturbation. Impacts to sediments and macroinvertebrates were closely correlated and, although greatest where sediment was directly deposited, extended over a wider (at least 1 km to the east) area than the deposition. Of the taxa comprising faunal assemblages, spionid polychaetes were most affected by the disposal, declining in abundance. These results, which tie the deposition and dispersal of coarse sediments on an ebb-tidal delta to changes in benthos, imply a biological cost that may be less than that of direct nourishment of biologically productive intertidal beaches. [ABSTRACT FROM AUTHOR]

Analysis of shoreline variability and shoreline erosion-accretion trends is fundamental to a broad range of investigations undertaken by coastal scientists, coastal engineers, and coastal managers. Though strictly defined as the intersection of water and land surfaces, for practical purposes, the dynamic nature of this boundary and its dependence on the temporal and spatial scale at which it is being considered results in the use of a range of shoreline indicators. These proxies are generally one of two types: either a feature that is visibly discernible in coastal imagery (e.g., highwater line [HWL]) or the intersection of a tidal datum with the coastal profile (e.g., mean high water [MHW]). Recently, a third category of shoreline indicator has begun to be reported in the literature, based on the application of image-processing techniques to extract proxy shoreline features from digital coastal images that are not necessarily visible to the human eye. Potential data sources for shoreline investigation include historical photographs, coastal maps and charts, aerial photography, beach surveys, in situ geographic positioning system shorelines, and a range of digital elevation or image data derived from remote sensing platforms. The identification of a "shoreline" involves two stages: the first requires the selection and definition of a shoreline indicator feature, and the second is the detection of the chosen shoreline feature within the available data source. To date, the most common shoreline detection technique has been subjective visual interpretation. Recent photogrammetry, topographic data collection, and digital image-processing techniques now make it possible for the coastal investigator to use objective shoreline detection methods. The remaining challenge is to improve the quantitative and process-based understanding of these shoreline indicator features and their spatial relationship relative to the physical land-water boundary. [ABSTRACT FROM AUTHOR]

The US Geological Survey is systematically analyzing historical shoreline changes along open-ocean sandy shores of the United States. This National Assessment of Shoreline Change Project is developing standard repeatable methods for mapping and analyzing shoreline movement so that internally consistent updates can periodically he made to record coastal erosion and land loss along US shores. Recently, shoreline change maps and a report were published for states bordering the Gulf of Mexico. Long-term and short-term average rates of change were calculated by comparing three historical shorelines (1800s, 1930s, 1970s) with an operational mean high water shoreline derived from lidar (light detection and ranging) surveys (post-1998). The rates of change, statistical uncertainties, original shorelines, and complementary geographic information system layers, such as areas of beach nourishment, are available on an Internet Map Server (IMS). For the Gulf of Mexico region, rates of erosion are generally highest in Louisiana along barrier island and headland shores associated with the Mississippi delta. Erosion also is rapid along some barrier islands and headlands in Texas, whereas barrier islands in Mississippi are migrating laterally. Highest rates of erosion in Florida are generally localized around tidal inlets. The most stable Gulf beaches generally are along the west coast of Florida, where low wave energy and frequent beach nourishment minimize erosion. Some long beach segments in Texas have accreted as a result of net longshore drift convergence and around tidal inlets that have been stabilized by long jetties. Individuals and some communities have attempted to mitigate the effects of erosion by emplacement of coastal structures, but those efforts largely have been abandoned in favor of periodic beach nourishment. [ABSTRACT FROM AUTHOR]

The Barataria-Terrehonne Estuarine System (BTES) in southeast Louisiana is one of the most vulnerable areas to coastal land loss in the United States. Comprising more than four million acres of wetlands, bayous. hays, and barrier shorelines, about 682 species of birds, fish, mammals, reptiles, and amphibians plus numerous species of invertebrates, including shrimp, oysters, and crabs, live or visit the BTES. It has the highest land loss rate and some of the most rapidly eroding barrier islands in the United States. Annual wetland loss rates ranged from 18 to 22 mi'²/y in the last 50 years in the BTES, representing at least one-half of the land loss in the entire state. The wetlands and shallow estuarine waters of the BTES are extremely productive, supporting diverse recreational opportunities and one of the largest commercial fishing industries in the country. These industries, with a large share coming from the BTES, generate more than $2 billion annually in fish and wildlife-associated activities, making the BTES a critical component of Louisiana's and the nation's economy. Unfortunately, Louisiana's wetlands are deteriorating rapidly, severely threatening the sustainability of the entire system and the assets of its renewable resources. As the barrier islands and wetlands of the BTES degrade and are lost, important habitat for renewable resources that support these industries will be gone. To preserve and protect these resources, restoration of wetlands and barrier shorelines is essential. Although the BTEB is only one piece of coastal Louisiana that is at stake, this paper focuses on the area to illustrate the richness of Louisiana's renewable resources and coastal environments, and the challenges that all coastal communities will face in the future. [ABSTRACT FROM AUTHOR]

Changes of sea-level, retreat of shorelines have occurred throughout geological times. They have taken a special significance since Man has appeared. Man has been simultaneously awed by the sea and attracted by its shores. He has consistently attempted to protect his settlements against the onslaughts of the sea. Coastal defenses can be traced back to remote times. It is probable that dams or walls were erected before the Frisiana did, but their "defenses" were described by Pliny, and, jusqu'a preuve du contraire, are considered as the first "dike builders". Earthen artificial hillocks are the forerunners of stone constructions built to hold back the advances of the sea, particularly when sizeable areas of land were gobbled up by the waters along coasts, but also in estuaries, witness i.e. the Dutch Verdronken Land van Saeftingen. The grains, seawalls, breakwaters and the like proved to be illusory shields, to solve little, but to create new problems. Engineers and scientists tried different approaches, inspired by Nature's own ways, nourishment for instance. Other methods are being hoped. They must as well consider the economic and social impacts of coastal erosion. The paper follows the historical evolution of man's attempts to retain his "land". [ABSTRACT FROM AUTHOR]