Abstract

Potential future increases in flooding due to climate change need to be taken into consideration when designing flood defences or planning new infrastructure or housing developments. Existing guidance on climate change allowances in Great Britain was based on research that developed a sensitivity-based approach to estimating the impacts of climate change on flood peaks, which was applied with catchment-based hydrological models. Here, the sensitivity-based approach is applied with a national-scale grid-based hydrological model, producing modelled flood response surfaces for every river cell on a 1 km grid. This provides a nationally consistent assessment of the sensitivity of flood peaks across Britain to climatic changes. The flood response surfaces are then combined with the most recent climate change projections, UK Climate Projections 2018 (UKCP18), to provide location-specific information on the potential range of impacts on floods across the country, for three flood return periods, three future time-slices and four emissions scenarios. An accompanying web-tool provides a convenient way to explore the large amount of data produced. Consideration is now being given to how to use the latest work to update guidance on climate change and flood peaks, including a workshop held to gather stakeholder views.

۱٫ Introduction

One of the ways in which climate change may particularly impact on society and the natural environment is through changes in river flows, especially extreme high or low flows. Floods are a significant risk globally, and the potential for climate change to increase the magnitude and frequency of flood events is a major concern (Klijn et al., 2015). The few global studies available suggest that flood hazard will increase over about half the globe, but with significant spatial variability (Jim´enez Cisneros et al., 2014). In Britain, the general conclusion is that flooding is likely to increase in future (Bell et al., 2012, 2016; Kay et al., 2015; Collet et al., 2018b). Indeed, there is some evidence that recent flood events have already been influenced by climate change (Kay et al., 2011, 2018). Thus in Britain there is specific guidance available to both flood management authorities and local planners, which aims to help them allow for the potential impacts of climate change when managing flood risk (Reynard et al., 2017).