1. How Deep is Wave Ravinement: Moving Beyond the Break-In-Slope Proxy
Antonio B. Rodriguez, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC 28557
The depth of wave ravinement, which is the depth where erosional wave processes can no longer rework coastal lithosomes, is assumed to be equal to the depth of the shoreline break-in-slope; however, this has never been rigorously examined. We are testing this by directly measuring ravinement depth in a variety of estuarine focus areas along the Newport River Estuary and Bogue Sound, North Carolina. A Riegl 3-D laser scanner is being used to directly measure shoreline movement and morphologic changes to an erosional scarp through time.
Left: Digital photograph (top), point cloud (middle), and digital elevation model (bottom) of the erosional scarp at the Pine Knoll Shores fringing marsh site. The method images the position and morphology of the scarp well, but has difficulty resolving the true elevation of the marsh top due to high-density vegetation cover.
Right: Digital elevation models of the same area of marsh edge in October 2007 (bottom) and March 2008 (middle). The two maps were subtracted (top) to show change with shades of red being erosion or loss of elevation, white being no change, and shades of green being accretion or a gain of elevation. The area of marsh shown is only about 2 m2 and measured changes in elevation are not more than about 22 cm.