The fate of dumped sediments monitored by a high-resolution multibeam echosounder system, Weser Estuary, German Bight

摘要

With the development of high-resolution multibeam echosounder systems (MBES) for surveying shallow-water areas a new tool is available to monitor rapid changes in seabed morphology as, e.g., caused by the dumping of dredge spoil in coastal waters. In this study, four data sets of repeated bathymetric surveys with a MBES were processed and analyzed. The data were collected in a 1.94-km(2) dumping site in the outer Weser Estuary (German Bight). Between June and December 1998, 2.6 million m(3) of dredged sediment were deposited there. The bathymetric maps generated in the course of this study reveal features such as subaqueous dunes, scour holes, and mounds of dumped dredge spoil. The mean water depth decreased by about 1 m during the dumping period. Furthermore, difference grids showing changes in sediment volume allowed a calculation of the sediment budget for the monitored area. After a time period of only 5 months, 0.5 million m(3) of the originally dumped 2.6 million m(3) of dredge spoil had already been removed from the dumping site. [References: 35]