Large-scale attribution of trend in UK flood flow data

The objective of this study is to undertake a preliminary investigation of trend in annual maximum series of peak flood data in the United Kingdom, as a precursor to developing a more complete procedure for non-stationary flood frequency estimation. A fifth of the trends in series that are at least 20 years long are significant at the 5% level (of in total 388 series). Most of the significant trends are positive, and are located in the north and west. The largest positive trends occur for short records in the most recent decades. Trends were also investigated for various subsets of the data, based on different catchment characteristics. There is an indication that the range of trend values observed for urban catchments is larger than the range observed for the rural subset, and that storage of water, whether in lakes and reservoirs or in permeable geology, has an ameliorating effect on trend magnitude.