MORPHODYNAMIC IN THE ELBE ESTUARY AS SEEN BY ERS SYNTHETIC APERTURE RADAR Edzard Romaneessen; Susanne Lehner; Andreas Niedermeier; Jochen Horstmann

摘要

The intertidal area of the German Bight is continuously changing its topography due to morphodynamic processes. This fact has serious impact on the German waterways, requiring a huge amount dragging with costs of about 80 mio DM per annum. In order to better monitor these morphodynamic processes and to continuously update the changing bottom topography, Synthetic Aperture Radar (SAR) data of the European Remote Sensing Satellite (ERS)-l and 2 are used in the estuary of the river Elbe. The SAR is an active sensor and therefore very useful for this study as it is possible to extract the land water boundary - the shoreline - during all weather conditions as well as during day and night. In this paper a combination of wavelet and active contour model is used to extract the shoreline information from 12 ERS SAR images acquired between 19 December 1996 and 25 July 1998. These shorelines are combined with hight information from the nearby tide gauge at Cuxhaven Steubenhoeft and interpolated to DEM of the small sandbank Medemsand. The comparison with a conventional generated DEM provided by the German Federal Waterway Engineering and Research Institute (BAW) using using vessel mounted echo sounder measurements from 1997 show a general very good agreement. Difference between both images can be explained by changes in the bottom topography due to morphodynamic processes.