Analysis of Sea Cliff Erosion Measured Using UAV Photogrammetry

The erosion of coastal chalk cliffs is a significant concern for communities in Northern Europe, with rates of retreat varying widely depending on local conditions. This study presents six years of UAV photogrammetry monitoring of chalk cliffs in Sussex, UK, producing 2.5D change detection maps to quantify erosion at Telscombe and Peacehaven. The results demonstrate a strong correlation between rates of lower-cliff erosion and wave energy at Peacehaven, with an r² value of 0.82. However, periods of intensive mass-wasting can render these relationships unreliable. The relationship for Telscombe, which experiences much more mass-wasting, demonstrates an r² of 0.37, which improves to 0.48 with the removal of an outlier. Cumulative erosion patterns follow a gradualistic trend, superimposed by episodic mass-wasting, with lower-cliff erosion rates increasing by approximately 3.2 times during storm-forced high-energy intervals compared to stable periods. A similar pattern is seen for mass-wasting events, although erosion intensities may be more than 6 times greater during periods of storminess. These findings highlight the role of storminess in accelerating erosion in the coastal zone.