Simulating the Shore and Cliffs of North Norfolk

Abstract

This chapter describes geomorphic modelling of the main Norfolk study area, the 50 km of the coast between Blakeney Spit and Winterton Ness, specifically the eroding cliffs, shore platforms, beaches, dunes and coast protection structures. The models represent both the natural eroding coastal system and past and future management interventions. Numerical experiments are also used to explore the possible dynamics of this coast if it were in a natural state. The ‘reduced complexity’ modelling tool Soft Cliff and Platform Erosion (SCAPE) is core to the analyses. It is described, along with the development of the quasi-three-dimensional Norfolk model. This model links marine hydrodynamic models to those of cliff failure, coastal flooding and economic risk. These links are described, along with the cliff instability module, the representation of beach fluctuation and beach nourishment (both natural and artificial). Results are shown to illustrate processes operating at a range of scales, including (millennial scale) emergence of the shore profile and beach volumes; (century scale) foreshore lowering, sensitivity to variations in rock strength, sediment transport potential and rate of sea-level rise; and (decadal scale) growth of wave impact forces, emergence of large-scale sand waves, probability density functions of beach volume, probabilistic cliff recession and the effects of beach nourishment. The benefits of such ‘reduced complexity’ modelling in general are highlighted. These include a deeper understanding of the coastal geomorphology, improved predictability, long-term model stability and ready coupling to other models. The approach is also relatively quick to apply and so can be implemented in practitioner studies, and the results are informing coastal planning in North Norfolk. Important features of the work include its large scale, which the coastal management process greatly needs, and the potential to use probabilistic methods, which allow economic risk to be derived to inform management decision-making. In terms of the Tyndall Coastal Simulator, the SCAPE model was a key element in linking the offshore conditions to human consequences (flood and erosion risk). It stresses the mediating role of coastal geomorphology in this link. Depending on how the coast is managed, those geomorphic processes can enhance (via erosion) or reduce (via accretion) these risks. The beach volumes were a direct input to the inundation analysis (Chap. 8 ), which together with the clifftop position informed the risk analysis (Chap. 9 ).