44947-AC8
How Deep is Shoreface Wave Ravinement? Moving Beyond the Shoreface Toe Proxy
The depth of wave ravinement, which is the depth where erosional wave processes can no longer rework coastal lithosomes, is assumed to equal the depth of the shoreline break-in-slope; however, this has never been rigorously examined. We are testing this by directly measuring ravinement depth, using an innovative approach, in a variety of estuarine focus areas along the North Carolina coast, including the Newport River Estuary, Bogue Sound, and Albemarle Sound. Fringing marsh environments are separated into 4 types based on paleodepositional, geographic, and hydrologic setting. Paleodepositional environments examined included flood-tidal delta, barrier island, washover fan, and bay-head delta. During year 1, core transects were collected along fringing marshes and high-resolution surface-elevation data were obtained. During year 2, cores for 210Pb analyses and 3-D laser-scanning data were collected from the marshes. These data are being used to constrain marsh accretion and erosion. Laser-scanning data were collected in the fall of 2007 and the spring of 2008 with the objective of quantifying morphologic changes to the marsh edge. The high-resolution grids of surface elevation were subtracted and resolve cm-scale changes to the erosional scarp at the marsh edge.
Grids of seismic data were also collected from the Newport River Estuary and Albemarle Sound around where small tributaries discharge into the estuary. Each tributary incised during the last lowstand in sea level and this paleotopograpy was altered by ravinement processes during the subsequent rise in sea level. By comparing the morphology of the subaqueous stretch of the paleochannels with the subaerial portion of the paleochannels and adjusting for grade, ravinement depth will be calculated.
This project supported one undergraduate summer researcher (Emmit Keeler) and one PhD student (C. Robbin Mattheus) during year 1 and Robbin Mattheus during year 2. The grant also helped the PI reestablish his coastal research program at the UNC.
