Utilizing a Chirp Sonar to Accurately Characterize Newly Deposited Material atthe Calcasieu Ocean Dredged Material Disposal Site, Louisiana

摘要

The distribution of dredged sediments is measured at the Calcasieu Ocean DredgedMaterial Disposal Site (ODMDS) using a chirp sonar immediately after disposal and two months later. Subbottom reflection data, generated by a chirp sonar transmitting a 4 to 20 kHz FM sweep, is processed to increase the vertical resolution of subbottom images from 4 cm to 1 cm. The distance between the sediment-water interface reflection and that generated by the underlying sediments is measured to generate contour maps of dredge material thickness. The strength of the sediment-water interface reflection is used to predict the mean grain size and bulk density of the surficial sediment layer. Contour maps of mean grain size, bulk density and sediment thickness provide the spatial and temporal movement of the dredged material.