Quantifying Uncertainty in the Modelling Process; Future Extreme Flood Event Projections Across the UK

With evidence suggesting that climate change is resulting in changes within the hydrologic cycle, ability to robustly model hydroclimatic response critical. This paper assesses how extreme runoff—1:2- and 1:30-year return period (RP) events—may at a regional level across UK by 2080s (2069–2098). Capturing uncertainty modelling chain, flow projections were extracted from EDgE (End-to-end Demonstrator for improved decision-making water sector Europe) multi-model ensemble: five Coupled Model Intercomparison Project (CMIP5) General Circulation Models four hydrological models forced under emissions scenarios Representative Concentration Pathway (RCP) 2.6 RCP 8.5 (5 × 4 2 chains). Uncertainty value parameterisation was captured through consideration of two methods: generalised (GEV) logistic (GL). The method applied 192 catchments aggregated eight regions. results suggest that, 2080s, many regions could experience large increases runoff, with maximum mean signal +34% exhibited East Scotland (1:2-year RP). Combined increasing urbanisation, these estimates paint concerning picture future flood landscape. chain found increase though (EV) parameter becomes dominant RP (exceeding 60% some regions), highlighting importance capturing both associated EV ensemble uncertainty.