This dataset is a set of 24 gridded netcdf files, each including data describing a total of 14,400 widespread flooding events across mainland GB, with event selection based on a peaks-over-threshold approach. The data describes peak river flow in m3/s and the associated annual probability of exceedance for each 1km grid-square on the GB river network. The data is extracted from daily time series data from the Grid-to-Grid model, using UKCP18 12km regional projections from 12 members of a perturbed parameter ensemble, over the periods Dec 1980 – Nov 2010 and Dec 2050 – Nov 2080 (based on 360-day years). Multi-day events were summarised by taking cell-wise flow maxima. This data was generated for use in analysis of risk through catastrophe modelling using the Future Flows Explorer. It was generated and interpreted by UKCEH, working with Sayers & Partners Consultancy, as part of the AquaCAT project, part of the UK Climate Resilience Programme. Full details about this dataset can be found at https://doi.org/10.5285/26ce15dd-f994-40e0-8a09-5f257cc1f2ab