The use of statistical downscaling to generate scenarios for modelling the impacts of climate change on the frequency and magnitude of floods in the UK

Large uncertainties remain about the precise nature of changes to the worldŠs climate from global warming, particularly with regard to possible changes at a regional or local level and to changes in the climate extremes that produce catchment flooding. Such changes might include more frequent short-duration, high-intensity rainfall or more frequent periods of long-duration, sustained rainfall of the type responsible for the Autumn 2000 floods in the UK. Nevertheless, the Department for the Environment, Food and Rural Affairs (Defra) are required to issue guidance on climate change for flood defence scheme appraisal. The research described in this paper has been funded by Defra and the Environment Agency to inform the development of policy and guidance on climate change impacts on flooding. The research uses improved catchment modelling capabilities using continuous flow simulation and climate change scenarios generated from statistical rainfall models and output from regional climate models. This paper will present the modelling framework and describe the development of the statistically-derived scenarios using the Statistical Downscaling Model (SDSM) developed byWilby et al., 2002. These scenarios, and their impact on the flood regime of a range of UK catchments, will be compared with those derived from the output of the Hadley Centre Regional Climate Model.