APPLICATIONS OF CHIRP SONAR ACOUSTIC REFLECTION COEFFICIENTS FOR BOTTOM SEDIMENT CHARACTERIZATION: RESULTS FROM THE UPPER DELAWARE ESTUARY
This study is part of a larger sedimentological and geophysical survey of the upper Delaware Estuary that was conducted during 2001-2002 by the University of Delaware in cooperation with the Delaware River Basin Commission (DRBC). The overall purpose of the survey was to acquire geologic data pertinent to hydrodynamic and sedimentation models implemented by DRBC to develop a Total Maximum Daily Load for PCBs in the estuary. The industrialized sector of the river-estuary between Burlington, New Jersey and New Castle, Delaware was systematically surveyed using sidescan and chirp sonars. A total of 217 kilometers of sonar tracklines were collected, covering 100% of the estuarine floor below the 5-meter isobath. Sidescan backscatter patterns and grain-size data, based on the grab samples, were used to develop interpretations of bottom sedimentary environments with regard to dominant sediment type and mode of transport. The four major environments identified were reworked bottom, fine-grained deposition, coarse-grained bedload, and non-deposition or erosion. The chirp reflection coefficient correlation with sediment type described in this study further constrains these estuarine sedimentary environments.