Despite much research on the many processes that erode rocky coastal cliffs, accurately predicting the nature, location and timing of coastline retreat remains challenging. This is also confounded by the apparently episodic nature of cliff failure. 

Coastline retreat via progressive failure of rocky coastal cliffs

The dominant drivers of coastal erosion, marine and sub-aerial processes, are anticipated in future to increase, so understanding their present and combined efficacy is fundamental to improving predictions of coastline retreat.

The researchers captured change using repeat laser scanning across a series of near-vertical rock cliffs on the UK North Sea coast over 7 years to determine the controls on the rates, patterns and mechanisms of erosion.

They say they have documented for the first time that progressive upward propagation of failure dictates the mode and defines the rate at which marine erosion of the toe can accrue retreat of coastline above; notably a failure mechanism not conventionally considered in cliff stability models.

Propagation of instability and failure operates over decadal timescales, and is moderated by local rock mass strength and the time-dependence of rock fracture.

Once initiated, failure propagation can operate ostensibly independently to external environmental forcing, and so may not be tightly coupled to prevailing conditions, which holds implications for modeling future coastal change.

Paper: Nick J. Rosser et al., Department of Geography, Durham University. DOI: 10.1130/G34371.1.