A hybrid approach to model shoreline change at multiple timescales

The paper describes the development of a hybrid behaviour-oriented/data-driven shoreline evolution model. The model is based on a form of advection–diffusion formulation widely known to describe shoreline change. The approach breaks down the model governing equation into two parts, one describing the contribution from time-averaged wave-driven processes through a spatially varying diffusion coefficient and the other describing time-varying wave contributions and all other processes that contribute to shoreline change, through a source function. Both the diffusion coefficient and the source function are site-specific and unknown. Historic incident wave measurements are used to determine the diffusion coefficient at a given site. The source function is derived by the inverse solution of the model governing equation using historic shoreline surveys. The method is demonstrated for Colwyn Bay beach at Conwy Bay in North Wales, UK. For drift-dominated shorelines, the technique can isolate the contributions of cross-shore and long-shore transport to shoreline change over a range of timescales, which is critical in implementing coastal defence measures.