Coastal cliff monitoring and analysis of mass wasting processes with the application of terrestrial laser scanning: A case study of Rügen, Germany

An active landslide, affecting a composite sea cliff section of the island of Rügen, Germany was investigated and monitored using terrestrial laser scanning. Biannual surveys were performed from 2006 to 2011. High resolution scans were used to delineate landslide extensions, monitor the spatial and temporal changes, and evaluate the processes of mass wasting along the cliff section. Between May 2006 and May 2011 the multi-temporal analysis documents a strong landward progression of the landslide that resulted in an increase in the planimetric area by 32%. In the same period, 9365 m3 of soil volume has been removed primarily due to rainfall triggered surface runoff erosion and the resulting slumping. This volume loss correlates with the preferential erosion of weak and unconsolidated sediments building up the major part of the cliff face. This produced a maximum cliff top retreat of 17.32 m with an average retreat rate of 3.46 m yr− 1.The quantification of the mass wasting processes and cliff top retreat demonstrates the substantial effect of local cliff lithology on slope stability, and supports a prognosis of the near future development of the landslide. Furthermore, the absence of local wave attack indicators or human activity highlights the major role of subaerial processes in the erosion of the sea cliff. These results can be transferred to cliff locations in the urbanised cliff top area nearby that currently suffer similar cliff erosion processes and episodic events of large cliff top retreats. The study therefore provides reliable data for the local authorities in charge of hazard assessment and planning and implementation of adaptive countermeasures.