Development of an integrated soft cliff model to determine the impacts of environmental and climatic change on coastal recession

Abstract

Understanding soft cliff systems is a significant challenge owing to the complex recession process and the need to quantify future responses to climate change. Process-based geomorphic modelling provides a key method for developing our understanding. However, existing models are frequently criticised for their simplified treatment of the cliff. Therefore, the overriding aim of this research was to contribute towards the development of a more integrated model. To facilitate this, this research has applied, evaluated and refined the SCAPE (Soft Cliff and Platform Erosion) model to a study frontage of variable lithology and coastal planshape on the south west coast of the Isle of Wight (UK). The initial model appraisal highlighted the need to further understand and quantify the role of variable material strength on shore platform geomorphology and rates of cliff toe retreat. The model was subsequently refined and demonstrated that outcropping layers of variable material resistance about mean sea level are a key control on the rates of cliff erosion, particularly for low sediment frontages. Weaker layers were found to result in an asymmetric increase in retreat in comparison to a more resistant layer of the same characteristics owing to the contrasting effects on the shore platform slope. This emphasises the importance of not extrapolating historic rates of retreat across frontages of variable lithology. Coastal management studies must consider relative changes in material resistance up the cliff face, the thickness of variable layers and the rate of sea-level rise to determine the magnitude of impact and duration of exposure.

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ORCID for R.J. Nicholls: orcid.org/0000-0002-9715-1109

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