UK flood risk under a changing climate

This study presents a 30 m model of UK flood hazard that considers fluvial, pluvial and coastal sources of flooding. Each of the three sources of flooding are simulated through a hydrodynamic model utilising a number of methodologies and datasets developed in this study, including a new hydrography dataset for Great Britain, a blended Digital Terrain Model (DTM) consisting of LiDAR and open source terrain datasets and a new discharge model for Great Britain. Alongside these, the study incorporates leading datasets including sub-daily river, rainfall, tidal and sea level datasets alongside national flood defence datasets. A defence detection algorithm is also applied to identify flow control structures from high resolution LiDAR terrain data. Results from the hazard model are validated against national scale flood maps at both a building and footprint scale. Future rainfall estimates are then taken from the UK Climate Projections 18 (UKCP18) to directly estimate changes in rainfall for a number of future time horizons and climate scenarios. Hydrological models are then simulated to calculate changes in river discharge which are then used to perturb boundary conditions in the hydrodynamic model. Future estimates of sea level change are used to perturb the coastal boundary conditions. Combined, these future estimates allow us to directly model changes in UK flood risk for fluvial, pluvial and coastal flooding. We use these findings to identify parts of the UK that are expected to see the greatest changes in flood risk resulting from these future projections.