A flood risk analysis model with topographical inundation and life-loss

Quantified models of flood risk that incorporate an explicit representation of the performance of flood defence infrastructure are becoming an increasingly important component of efforts to manage flood risk. The models have been applied to support a wide range of decisions, including long-term strategic planning, assessment of investment needs and shorter-term asset management. The model currently applied in practice by the Environment Agency in England and Wales makes a number of simplifying assumptions to achieve computationally practical run-times. One of these simplifications relates to the volume-based flood-spreading algorithm that is applied. This paper describes the implementation of a new time-based inundation model within the existing risk analysis modelling approach. The new inundation model offers a significant increase in the representation of the physical processes within the flood simulation component of the risk analysis model. It also offers new outputs in terms of estimates of maximum depths and flood velocities. Velocities are known to be an important factor in flood-related fatalities. A simplified method to estimate life-loss has been combined with new output from the improved inundation model to illustrate how estimates of risk to life could be provided.