Multi-Sensor Remote Sensing of historical landuse areas in the German Wadden Sea

375 years ago, a big storm surge in the German Bight of the North Sea destroyed farmland, farms, and villages, and killed a great number of both cattle and men. The big (second) “Mandränke” of 1634 is still one of the most famous storm surges in the area of the North Frisian Wadden Sea. By the early seventeenth century, this part of the Germany Wadden Sea was a swampy area, which was only little protected against marine impact by higher sand dunes in the west. First settlements in this marshland date back to the Roman times. In the Middle Ages, farmsteads and villages were built, surrounded by farmland and also floodplain forests. The houses were mostly built on dwelling mounds, protected by small dikes, and ditches were built to take out the water of the farmlands. Over the years, great parts of this former agricultural area have been buried by muddy and sandy sediments, which nowadays form the German Wadden Sea, and which fall dry once during each tidal cycle.
Under the permanent action of the tidal forces, morphodynamics take place, the muddy and sandy marine sediments are partly driven away, and traces of former peat cutteries, farmland, and settlements appear again on the bottom of the Wadden Sea. These sedimental structures show distinct biological effects and are often marked by benthic organisms. Since those areas are difficult to reach and, thus, to observe from the ground, spaceborne sensors have proven to be advantageous for a systematic observation of the residuals of those historical places.
We present first results of our analyses of spaceborne optical and SAR data, which show imprints of former settlements in the North Frisian Wadden Sea. For the first time, data from high-resolution SAR sensors working at L and X band (PALSAR and TerraSAR-X, respectively) are used to demonstrate that residuals of former agricultural areas can still be detected from space. The data are complemented by aerial photographs and in-situ data.
This work is partly supported by the German national project DeMarine (50 EE 0817)