Climate change and fluvial flood peaks
Updates to river flooding projections using the latest climate change evidence
Documents
Project Summary
This project provides new projections of how river flooding may change due to climate change. This information will help the Environment Agency and others who manage future risk from flooding.
Background
Planners need information about how river flooding may change so that they can prepare accordingly. Earlier work (FD2020) developed a way to estimate the impacts of climate change on flood flows and applied it to 154 catchments across Great Britain. Some of these catchments were found to be more sensitive than others to changes in rainfall and therefore responded faster to related climate change impacts. By grouping the catchments by their sensitivity to climate change impacts, it was possible to estimate the response of other catchments and from them, the response of the larger river basin regions of which they are part.
However, the different steps in the analysis generated uncertainty. This new project reduces that uncertainty by combining information on catchment sensitivity to climate change with a national scale model that represents all catchments. To be consistent across Great Britain this was a joint study with Natural Resources Wales and the Scottish Environmental Protection Agency (SEPA).
Method
The model used was Grid-2-Grid (G2G), which is a grid based hydrological model that generates river flow information for every 1 km square of the river network of Great Britain. It also uses the most recent UK Climate Projections 2018 (UKCP18), whereas the previous work used UK Climate Projections 2009 (UKCP09).
The method developed in this project created a large amount of data having modelled a wide range of possible changes to flood peaks for every 1 km square of the river network. It also modelled three future time horizons and different greenhouse gas emissions scenarios. These projections were then compared with historic flood peaks to calculate the relative change in the flood peak caused by the projected changes in rainfall. The large number of model projections also allowed us to calculate the probability of different changes in future flood peaks.
Results
The results can be viewed through an interactive web tool that provides a convenient way of exploring the wealth of information at different locations across Great Britain.
In addition, the 1 km scale flood peak change results were used to create relative change values for the larger water catchments in England. These change values are included in guidance for use by the Environment Agency, English flood risk management authorities and developers who undertake flood risk assessments.
The method used to derive these management catchment values is described in the supplementary report.
Project Information
Project manager: Stuart Allen, Chief Scientist’s Group
This project was funded by the joint Flood and Coastal Erosion Risk Management Research and Development Programme and delivered by UK CEH.
Email: fcerm.evidence@environment-agency.gov.uk