Assessing PS-InSAR ground motion data toward stability monitoring of coastal flood protection dikes

Abstract

Sea level rise caused by climate change represents a challenge to coastal flood protection measures, particularly in regions such as the federal state of Schleswig-Holstein. Large parts along the North Sea coast are protected by dikes and offshore islands provide additional shelter to the hinterland, which often lies just above or even beneath sea level. We have examined InSAR time series data from the German Ground Motion Service along the entire west coast dike route from the Danish border to Wedel. We want to estimate how these data can be used to detect and monitor ground motion processes related to dikes, especially in cases where PS (persistent scatterer) are irregularly distributed. We found, that mainly those parts of the dikes can be monitored by PS interferometry where the seaward dike base is shielded by heavy armourstone acting as sufficient back-scatters for radar waves. Here, ground motion processes induced by additional load of reinforcing construction work can be observed. In some regions the dikes are influenced by long-term, large-scale subsidence. We performed statistical analysis on low pass filtered PS time series to automatically identify significant ground motion and/or ground motion events within a local area of interest. Preliminary results suggest, that we may be able to identify dike segments which show signs of anomalous ground motion and thus should be monitored closely.