Probable maximum flood: the potential for estimation in the UK using ReFH2

The current reservoir safety guidance within the UK recommends the use of the FSR/FEH rainfall-runoff model to estimate PMF (probable maximum flood) peak flows for reservoirs within the highest risk category (A). However, the FSR/FEH model has been superseded by the ReFH2 rainfall-runoff model for all other flood risk purposes in the UK. This study develops a new modelling framework for PMF estimation using ReFH2 by translating the assumptions made within the current FSR/FEH PMF procedure and applying these within the ReFH2 rainfall-runoff model. Peak flows from the methodology are compared with those from the FSR/FEH model for 400+ catchments. The study highlights the potential for ReFH2 to be used as the rainfall-runoff model for all return periods, up to and including the PMF, thereby paving the way for using the ReFH2 model for reservoir safety studies.