Using climate change projections in UK flood risk assessment

In the UK, a disparity exists between modelled future weather/climatic patterns and the assessment of climate change impact on flood risk in the UK statutory planning process. Specifically, the impacts of climate change on the physical characteristics of a river catchment (e.g. land-use change, vegetation cover, soil moisture) are not considered when generating climate change weighted design flood events to assess the potential impact of flooding on a development in the future. Instead, a UK-wide averaged perturbation factor is applied. In this paper, a method is tested to integrate climate change data from UK climate projections 2009 (UKCP09) into design flood estimation methods (ReFH) as part of the current planning process. Scenarios are developed for a single, critical duration, 1% probability (1-in-100 year) design flood event that reflects plausible changes in catchment physical parameters in the 2080s. Initial results suggest that a 1-in-100 year storm in the 2080s may be greater in magnitude, rise and recede faster, and be associated with greater depths of flooding than predicted using current flood risk assessment frameworks in the UK. This information could provide new information to help developers choose more sustainable, flood-resistant and resilient designs.