Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain.
Rising sea levels and increased storminess are expected to accelerate the erosion of soft-cliff coastlines, threatening coastal infrastructure and livelihoods. To develop predictive models of future coastal change we need fundamentally to know how rapidly coasts have been eroding in the past, and to understand the driving mechanisms of coastal change. Direct observations of cliff retreat rarely extend beyond 150 y, during which humans have significantly modified the coastal system. Cliff retreat rates are unknown in prior centuries and millennia. In this study, we derived retreat rates of chalk cliffs on the south coast of Great Britain over millennial time scales by coupling high-precision cosmogenic radionuclide geochronology and rigorous numerical modeling. Measured10Be concentrations on rocky coastal platforms were compared with simulations of coastal evolution using a Monte Carlo approach to determine the most likely history of cliff retreat. The10Be concentrations are consistent with retreat rates of chalk cliffs that were relatively slow (2-6 cm⋅y-1) until a few hundred years ago. Historical observations reveal that retreat rates have subsequently accelerated by an order of magnitude (22-32 cm⋅y-1). We suggest that acceleration is the result of thinning of cliff-front beaches, exacerbated by regional storminess and anthropogenic modification of the coast.
School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom; martin.hurst@glasgow.ac.uk.|British Geological Survey, Keyworth, Nottinghamshire NG12 5GG, United Kingdom.
Martin D
0000-0002-9822-076X
MD
Hurst
Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, United Kingdom.
Dylan H
0000-0002-4425-4702
DH
Rood
British Geological Survey, Keyworth, Nottinghamshire NG12 5GG, United Kingdom.
Michael A
MA
Ellis
Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80303.|Department of Geological Sciences, University of Colorado, Boulder, CO 80303.
Robert S
RS
Anderson
Environment Agency, Worthing BN11 1LD, United Kingdom.
Uwe
U
Dornbusch
cliffs; coasts; cosmogenic radionuclides; erosion; geomorphology