Erosional behaviour of a glacial till cliff coast in Stohl, Baltic Sea, Germany

Abstract

Erosional processes at an approximately one kilometre long coastal cliff stretch were investigated. The cliff is located at the German Baltic Sea coast and mainly made up of glacial till from the last glaciation. Glacial deposition and folding in multiple advances resulted in complex stratigraphy and locally diverse geology of at least two distinct glacial till complexes and intermediate layers of sand, now eroded by wave action and subaerial processes on the cliff face. To study the changes on the cliff, drone surveys were carried out roughly every month over three years and used to create elevation models with structure from motion. This data was combined with time series of water levels, wave characteristics and precipitation. Three main erosion processes could be identified: marine erosion at the cliff foot, surface runoff and mass movements. 13 marine erosion events are clearly connected to high waves and water levels. Surface runoff creates alluvial fan deposits at the cliff foot and is driven by precipitation. However, the correlation is not clear as the deposition depends on local properties and preconditioning and is very susceptible for marine erosion. The more than 400 detected mass movements cannot clearly be correlated with precipitation, most likely due to the local geology, but they show a distinct negative magnitude-frequency-relation and often follow marine erosion events at the cliff foot.