Monitoring of a Sea-Dike in Northern Germany by Means of ERS-1, ENVISAT/ASAR, and Sentinel-1 SAR Interferometry

Flood events are one of the most severe natural hazards threatening billions of people living in coastal areas. Synthetic aperture radar (SAR) interferometry can contribute significantly to civil security by providing a highly accurate tool for spatially explicit monitoring of flood protection structures. This article analyzes multitemporal SAR interferometry techniques like persistent scatterer interferometry and small baseline subset (SBAS) for C-band radar data in order to show the potential for a precise dike monitoring. These techniques not only achieve accuracies of few millimeters, but they also enable to reconstruct the deformation process in time. Thus, critical deformation processes can be identified timely and precautions can be taken to prevent dike bursts during flood events. In this article, sea dikes located at the North Sea coast in Germany are analyzed in order to show the potential but also the difficulties of this approach, using 34 ERS-1/2, 55 Envisat ASAR, and 44 Sentinel-1 scenes. All results point out that long-term deformation processes can be measured quite well. Due to decorrelation effects, the results on vegetated dikes are ambiguous. Applying SBAS to Sentinel-1 data is very promising to serve as a tool to precisely detect and understand deformation processes of dike bodies on large spatial scales.