Coastal cliff ground motions and response to extreme storm waves

Abstract

Coastal cliff erosion from storm waves is observed worldwide, but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs, limiting our understanding of cliff processes. Over January-February 2014, during the largest Atlantic storms in at least 60years with deepwater significant wave heights of 6-8m, cliff-top ground motions showed vertical ground displacements in excess of 50-100μm; an order of magnitude larger than observations made previously. Repeat terrestrial laser scanner surveys over a 2week period encompassing the extreme storms gave a cliff face volume loss of 2 orders of magnitude larger than the long-term erosion rate. The results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long-term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts.