A predictive Mesoscale model of the erosion and profile development of soft rock shores

The development, application and behaviour of a generic model of retreating soft rock (e.g. clay) shores is described. This represents a broad system, in coastal modelling terms, comprising shore platform, beach, tidal range, wave transformation, cliff and talus. The coast is divided into a series of representative cross-shore profiles, each of which is discretised into a column of elements. Erosion of a platform element at each timestep depends on its gradient. Material strength is dealt with as a calibration constant, wave forces are averaged over durations of a tide or hour and sediment transport is represented in bulk terms. Attention has been focussed on interaction between system parts and the emergence of system properties, in particular profile shape. This is allowed to develop towards dynamic equilibrium and is the principal means of model validation. The emergence of the profile shape is dominated by the distribution of wave scour by the tide and by interaction with a beach, if present. Because the model is process-based, it may be used to model the effects of climate change and engineering intervention. Yet it is also computationally inexpensive, so may be used to explore uncertainty through probabilistic application. The breadth of the included system, coupled with short run-times, enables predictions over timescales of decades, which we refer to as the Mesoscale. The model is used to explore the dynamics of retreating soft rock shore profiles and to predict future behaviour of a study site.