Delaware Bay Benthic Mapping Project: Using Highresolution Geophysical Methods To Map Bottom Habitat And Sub-Bottom Sediments

The Coastal Program of the Delaware Department of Natural Resources and Environmental Control is carrying out a bottom and sub-bottom imaging project to map the bottom habitat and subbottom sediments of Delaware Bay. A RoxAnn acoustic system measuring bay bottom hardness and roughness is correlated with ground-truth grab samples and video to classify bottom sediments. The RoxAnn data is being used to map the distribution of these sediments and has identified the spatial extent and relative density of oyster shell on the bay bottom. Sub-bottom profiles, collected using an Edgetech X-STAR chirp sonar system, are integrated with the RoxAnn data to constrain the thickness and continuity of bottom sediments and to map potential/past offshore sand borrow sites that can be/have been used for beach replenishment. The chirp data has been integrated with additional information from sediment cores to develop maps of suitable sand deposits for replenishment based upon location, thickness, overburden, and grain size. The morphology of select areas of the bay bottom is being mapped using a Reson 8124 multibeam bathymetric system. The system has been used to map high-interest areas including natural and artificial reefs, oyster beds, and critical fish habitat.