The topography comparsion between the year 1999 and 2006 of German tidal flat wadden sea analyzing SAR images with waterline method

The topographic differences in German Wadden Sea between 1999 and 2006 are compared and analyzed in this paper. The waterline method is used to generate topographic maps of this area with SAR images. 13 SAR images (from ERS-2) of the year 1999 and 14 SAR images (12 from ERS-2, 2 from ENVISAT_ASAR) of the year 2006 are analyzed. The SAR images captured at different dates are able to cover different tidal phases to represent the tidal flat. The waterlines are detected by a wavelet based edge detection algorithm, assigned with water level information from the operational water level model of the German hydrographic agency, corrected with water gauge data. The waterlines with water level information are interpolated into a regular grid to represent the intertidal topography of the Wadden Sea. The topographic maps, in large scale, are stable and correct. There are some significant changes at Gelbsand, Medemsand and Tertiussand. Sediment transport can be intended from these topographic maps.