Simplified two-dimensional numerical modelling of coastal flooding and example applications

In this paper we outline the development and application of a simple two-dimensional hydraulic model for use in assessments of coastal flood risk. Such probabilistic assessments typically need evaluation of many thousands of model simulations and hence computationally efficient codes of the type described here are required. The code, LISFLOOD-FP, uses a storage cell approach discretized as a regular grid and calculates the flux between cells explicitly using analytical relationships derived from uniform flow theory. The resulting saving in computational cost allows fine spatial resolution simulations of regional scale flooding problems within minutes or a few hours on a standard desktop PC. The development of the code for coastal applications is described, followed by an evaluation of its performance against four test cases representing a variety of flooding problems at different scales. For three of these cases an observed flood extent is available to compare to model predictions. In each case the model is able to match the observed shoreline to within the error of the of the observed flow, topography and validation data and outperforms a non-model flood extent prediction made using a simple Geographical Information System (GIS) technique.