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Deriving mechanisms and thresholds for cliff retreat in soft-rock cliffs under changing climates: rapidly retreating cliffs of the Suffolk coast, U.K.

Brooks, Susan M. and Spencer, T. and Boreham, S. (2012) Deriving mechanisms and thresholds for cliff retreat in soft-rock cliffs under changing climates: rapidly retreating cliffs of the Suffolk coast, U.K. Geomorphology 153-15 , pp. 48-60. ISSN 0169-555X.

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Official URL: http://dx.doi.org/10.1016/j.geomorph.2012.02.007

Abstract

Understanding changing thresholds and mechanisms for retreat in soft rock cliffs is important under changing climates. This can be achieved through combining detailed field observation, long-term process and morphological monitoring and numerical modelling. The cliffs of the Suffolk coast, southern North Sea have exhibited long-term (1883–2010) recession rates of 3.5 m a-1, rising to 4.7 m a-1 in the period 1993–2010. Annual to biannual ground survey data, and the application of GIS techniques to digitised records of changing shoreline position from historic maps and aerial photography, reveal considerable decadal-scale variations in cliff recession, within which are nested inter-annual fluctuations in rates of retreat. Archival datasets on significant periods of onshore winds and their interaction with high water levels (including the incidence of storm surges) and rainstorm events are used to determine thresholds for cliff base erosion and its propagation upwards through the cliff profile. In addition, the ‘GEO-Slope’ dynamic coupled hydrology-stability model is used to establish thresholds for cliff face failures driven by variations in rainfall inputs. Retreat mechanisms are complex, governed by cliff geology, both as a primary control on suction loss and through its interaction with basal marine conditions. The study allows a general model of cliff retreat for soft rock cliffs to be put forward, whereby a resistant basal platform is overlain by more erodible, weakly and moderately cemented sands and gravels. In this model, the varying balance between marine and terrestrial forcing factors are reflected in low (< 4 m a-1), intermediate (4–7 m a-1) and high (> 7 m a-1) modes of cliff retreat.

Item Type: Article
Keyword(s) / Subject(s): Coastal mass movements, Cliff hydrology, Shoreline retreat, Cliff morphodynamics, Storminess, Southern North Sea
School or Research Centre: Birkbeck Schools and Research Centres > School of Social Sciences, History and Philosophy > Geography, Environment and Development Studies
Depositing User: Administrator
Date Deposited: 20 Feb 2012 14:07
Last Modified: 17 Apr 2013 12:22
URI: http://eprints.bbk.ac.uk/id/eprint/4603

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