A new process–response coastal recession model of soft rock cliffs

Abstract

The development of cliff erosion predictive models is limited by the complex interactions between environmental processes and material properties over a range of temporal and spatial scales. Current models incorporate a stochastic representation of cliff behavior based on assumptions regarding the magnitude and frequency of events in a probabilistic framework. The new model presented here has been developed to incorporate the behavioral and mechanical characteristics of coastal cliffs which are dominated geologically by overconsolidated clays (tills) and an associated protective colluvial wedge. This model is capable of providing precise and stable responses to some of the inherent uncertainties in cliff recession processes including those caused by different failure mechanisms e.g. colluvium generation, groundwater and erosive tidal cycles. Material strength is incorporated using the unconfined compressive strength of the material that composes the cliff. Unlike previous models, a calibration parameter is restricted to account for uncertainties linked to marine processes. The mechanisms of cliffline retreat have been identified as slump and topple landslides. Once cliff material has fallen, colluvium formation at the cliff foot is incorporated into the model using three different procedures according to the geomechanical characteristics of the debris. The model is validated through profile evolution assessment at various locations of coastline retreat on the Holderness Coast, UK. Higher groundwater content also produces an increase in the number and size of the slope failures. The results represent an important step-forward in linking material properties to the processes of cliff recession.