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John W King - One of the best experts on this subject based on the ideXlab platform.
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assessing the impact of extreme storms on Barrier Beaches along the atlantic coastline application to the southern rhode island coast
Coastal Engineering, 2018Co-Authors: Lauren Schambach, Annette R Grilli, Stephan T Grilli, Reza M Hashemi, John W KingAbstract:Abstract In this work, we use the 2D model XBeach to dynamically simulate coastal erosion due to a synthetic 100-year storm impacting a typical North Atlantic Barrier Beach located in southern RI. This storm was extracted from the North Atlantic Coast Comprehensive Study (NACCS) database, based on results of an extreme value analysis of more than 1000 NACCS storms. XBeach parameters are first calibrated/validated by simulating Hurricane Irene (August 2011), for which both nearshore wave data and pre- and post-storm Beach profiles were available in the study area. Comparing results to observations allowed calibration of the wave asymmetry and skewness parameter ( γ u a = 0.3 ) in the model, resulting in a 6% mean relative error between the simulated and measured subaerial eroded volumes along 4 transects. In the 100-year storm XBeach simulations that include overwash, effects of land cover on Beach erosion, in particular vegetation, are assessed by specifying a spatially varying bed friction function of high-resolution land cover. Results show that healthy back-dune vegetation is essential to prevent the dune crest from being fully eroded down to its toe level. The predicted median 100-year eroded volume is 46 m3/m for the entire Barrier Beach, in good agreement with FEMA's empirical value of 50 m3/m at the two “official 1D transects” within the study area; mean post-storm reductions in dune crest elevations are in similar agreement. The model, however, predicts very large alongshore variations of these parameters, with eroded volumes over 1000 m3/m where breaching and the opening of surge channels occurs. Overall, dune segmentation simulated in the model for the 100-year storm appears to be realistic and consistent with dune topography and land cover. XBeach thus provides an improved 2D methodology for assessing the impact of extreme storms on Atlantic Barrier Beaches, predicting changes in dune morphology, and quantifying the protective role of vegetation, and effects of land cover in general.
Albert Falques - One of the best experts on this subject based on the ideXlab platform.
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rhythmic morphology in a microtidal low energy Beach
Geomorphology, 2019Co-Authors: Anna Mujalcolilles, Manel Grifoll, Albert FalquesAbstract:Abstract Observations of rythmic features along the inner side of the Trabucador Barrier Beach are coupled to two numerical models to unravel the mechanisms of its formation. The Trabucador is a long (6 Km) narrow (125 m) Barrier and microtidal Beach at the SW side of the Ebro delta (Catalonia). Its inner side is a low energy Beach with a sandy shallow terrace featuring an intricate alongshore rhythmic morphology. Sixteen aerial orthophotos from 1946 to 2014 have been analyzed and complemented with field observations from 1986 to present. This morphology is dynamic but it is usually characterized by: a) long finger transverse bars (LFTB) and b) large scale shoreline undulations (LSSU). The LFTB are thin and elongated with a length of the order of their spacing. They are intertidal and typically attach to the shoreline by a megacusp, commonly opening an anti-clockwise angle of 10°–40° with the shore normal. There can be many, up to 90, with both the mean and the most frequent alongshore spacing in the range 15–25 m. Spectral analysis always shows peaks in this range and sometimes additional peaks in the range 30–65 m that correspond to the spacing between the largest bars with smaller bars in between. The LSSU typically have wavelengths in the range 150–250 m. Their apexes sometimes coincide with the shore attachment of the largest bars but not always. Numerical modelling shows that both features could emerge out of feedbacks between hydrodynamics and morphology during the SW wind events involving a) deflection of the longshore current by the bars combined with the refractive wave focusing and b) gradients in total alongshore sediment transport rate triggering the high-angle wave instability.
John Pether - One of the best experts on this subject based on the ideXlab platform.
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Late Quaternary sedimentological history of a submerged gravel Barrier Beach complex, southern Namibia
Geo-Marine Letters, 2019Co-Authors: Megan J. Runds, Emese M. Bordy, John PetherAbstract:Through comprehensive seismic, stratigraphic, and sedimentological analysis, this paper describes the stratigraphic architecture of the late Quaternary sediments and depositional dynamics in a region ~ 3.5 km offshore of the current south-west Namibian coastline. The landscape evolution model of this area is based on 2D seismic reflection profiles calibrated to approximately 500 boreholes, which yielded sedimentary and seismic facies data of exceptionally high resolution. The data permitted the characterization of four sedimentary facies units and the reconstruction of the submerged landscape dominated by a Barrier complex. We compare this Barrier complex with the sediment bodies preserved along the adjacent coastline, and account for their geological evolution in response to late Quaternary relative sea-level fluctuations along the West Coast. The most noteworthy depositional units in the study area are the normal regressive coarse gravel Beaches trending shore parallel, with the primary gravel Barrier and its preserved coeval back-Barrier deposits that exceed 7 km in length along the coast. Based on the radiocarbon dates from the rarely preserved early flooding facies (14.0 and 13.3 ka BP), the primary Barrier complex formed during a stage of slowing rising relative sea-level subsequent to Meltwater Pulse 1A. Moreover, the Barrier Beach complex formed on a low-gradient palaeo-bathymetry slope that is punctuated by a break on its landward side (i.e., a regional knick point), which promoted the local accommodation of sediments. The preservation of the Barrier Beach complex and back-Barrier deposits is attributed to rapid relative sea-level rise, linked to the early Holocene Meltwater Pulse 1B between ~ 11.5 and 11.2 ka BP, and an increase in back-Barrier accommodation facilitated by the antecedent topography.
Rosalind Herlands - One of the best experts on this subject based on the ideXlab platform.
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Turtles and Tires: The Impact of Roadkills on Northern Diamondback Terrapin, Malaclemys terrapin terrapin, Populations on the Cape May Peninsula, Southern New Jersey, USA
1997Co-Authors: Roger Conant Wood, Rosalind HerlandsAbstract:A century ago overhunting of the northern diamondback terrapin, Malaclemys terrapin terra- pin, nearly extirpated populations in many parts of its range. More recently, coastal development has led to considerable habitat destruction, especially of traditional nesting sites on Barrier Beach islands. Along the Atlantic coast of New Jersey, the search for alternative nesting sites on highway embankments has resulted in large numbers of roadkills every nesting season. We have documented the annual mortality of nesting diamondback terrapins on the Cape May Peninsula of southern New Jersey from 1989 through 1995. A total of 4,020 roadkills were recorded on roads crossing or adjacent to our study area. Potentially viable eggs were recovered from carcasses and 32% were success- fully incubated. Since 1991 hatchlings have been headstarted for ten months and 782 (an 81% hatchling sur- vivorship) have been released into the salt marshes of the parents' origin. Roadkill mortality of adult females remains considerably higher than their rate of replacement, and we have noted a substantial decrease in num- bers of mature female terrapins in our study area. Diamondback terrapins, Malaclemys terrapin, include several subspecies within a unique genus and species of emy- did turtles. The terrapin is the only one of more than 270 extant species of turtles whose habitat is confined to coastal brackish (as opposed to fresh or truly oceanic) waters. The species' range is several thousand miles long but never more than a few miles wide, extending from the north-temper- ate zone into the subtropics, from Cape Cod, Massachusetts, through the Florida peninsula and Keys, to the Gulf Coast of the United States. The western terminus of its range has not been precisely deter- mined, but probably lies near Corpus Christi, Texas. Malaclemys terrapin ter- rapin (the focus of this report) is the northernmost of the seven described sub- species. It ranges from Cape Cod, Massachusetts, to Cape Hatteras, North Carolina.
Conor P Mcgowan - One of the best experts on this subject based on the ideXlab platform.
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a comparison of american oystercatcher reproductive success on Barrier Beach and river island habitats in coastal north carolina
Waterbirds, 2005Co-Authors: Conor P Mcgowan, Theodore R Simons, Walker Golder, Jeff CordesAbstract:Abstract American Oystercatcher (Haematopus palliatus) numbers along the east coast of the United States are declining in some areas and expanding in others. Researchers have suggested that movement from traditional Barrier Beach habitats to novel inland habitats and coastal marshes may explain some of these changes, but few studies have documented oystercatcher reproductive success in non-traditional habitats. This study compares the reproductive success of the American Oystercatcher on three river islands in the lower Cape Fear River of North Carolina with that of birds nesting on Barrier island Beach habitat of Cape Lookout National Seashore. There were 17.6 times more oystercatcher breeding pairs per kilometer on the river island habitat than Barrier Beach habitat. The Mayfield estimate of daily nest content survival was 0.97 (S.E. ± 0.0039) on river islands, significantly higher than 0.92 (S.E. ± 0.0059) on Barrier islands. The primary identifiable cause of nest failure on the river islands was flood...
