National Oceanic and Atmospheric Administration hydrographic survey data used in a U.S. Geological Survey regional geologic framework study along the Delmarva Peninsula

Pendleton, Elizabeth; Thieler, E. Robert; Danforth, William W.; Parker, Castle E.

doi:10.3133/ofr20141262

Cited by 4 publications

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“…These effects can occur on various length and time scales through both the effects of offshore bathymetric features on wave‐ and current‐induced flow patterns in the nearshore and also possible cross‐shore exchange of sediment between the nearshore and the inner‐shelf. Examples of where the geologic framework is strongly varying spatially are the inner shelves of Mississippi (Flocks et al, ), West Florida (Finkl et al, ), South Carolina (Denny et al, ), Delmarva Peninsula (Pendleton et al, ), and New York (Schwab et al, ). Such inner‐shelf areas have rarely been mapped in high resolution.…”

Section: Introductionmentioning

confidence: 99%

Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

et al. 2017

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Mechanisms relating offshore geologic framework to shoreline evolution are determined through geologic investigations, oceanographic deployments, and numerical modeling. Analysis of shoreline positions from the past 50 years along Fire Island, New York, a 50 km long barrier island, demonstrates a persistent undulating shape along the western half of the island. The shelf offshore of these persistent undulations is characterized with shoreface‐connected sand ridges (SFCR) of a similar alongshore length scale, leading to a hypothesis that the ridges control the shoreline shape through the modification of flow. To evaluate this, a hydrodynamic model was configured to start with the US East Coast and scale down to resolve the Fire Island nearshore. The model was validated using observations along western Fire Island and buoy data, and used to compute waves, currents and sediment fluxes. To isolate the influence of the SFCR on the generation of the persistent shoreline shape, simulations were performed with a linearized nearshore bathymetry to remove alongshore transport gradients associated with shoreline shape. The model accurately predicts the scale and variation of the alongshore transport that would generate the persistent shoreline undulations. In one location, however, the ridge crest connects to the nearshore and leads to an offshore‐directed transport that produces a difference in the shoreline shape. This qualitatively supports the hypothesized effect of cross‐shore fluxes on coastal evolution. Alongshore flows in the nearshore during a representative storm are driven by wave breaking, vortex force, advection and pressure gradient, all of which are affected by the SFCR.

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