Flood estimation by continuous simulation in the Don catchment, South Yorkshire, UK

An innovative technique has been used for flood estimation in a catchment study which was carried out for the Environment Agency The River Don drains a large port of South Yorkshire. On its major tributaries (the Rivers Rather and Dearne), flow regulators and artificial washlands ore used during extreme floods to delay and attenuate peak flows, allowing the peak on the Don to pass by first. The flood hydrology of the Don catchment is therefore unusual and cannot be adequately represented by conventional methods such as those in the Flood Estimation Handbook, Instead, a 1000 year series of hourly rainfall was generated using a stochastic rainfall model, This was converted to flow data using a set of probability distributed moisture rainfall-runoff models; therefore, inflows for a hydraulic model were created. This eliminated the need to make assumptions about a design flood event, leading to more robust flood estimates throughout the Don catchment. This approach could prove to be applicable to other UK or overseas studies, particularly on large or complex catchments, or in solving joint probability problems.