Drivers of future urban flood risk.

Managing urban flood risk is a key global challenge of the twenty-first century. Drivers of future UK flood risk were identified and assessed by the Flood Foresight project in 2002-2004 and 2008; envisaging flood risk during the 2050s and 2080s under a range of scenarios for climate change and socio-economic development. This paper qualitatively reassesses and updates these drivers, using empirical evidence and advances in flood risk science, technology and practice gained since 2008. Of the original drivers, five have strengthened, three have weakened and 14 remain within their 2008 uncertainty bands. Rainfall, as impacted by climate change, is the leading source driver of future urban flood risk. Intra-urban asset deterioration, leading to increases in a range of consequential flood risks, is the primary pathway driver. Social impacts (risk to life and health, and the intangible impacts of flooding on communities) and continued capital investment in buildings and contents (leading to greater losses when newer buildings of higher economic worth are inundated) have strengthened as receptor drivers of urban flood risk. Further, we propose two new drivers: loss of floodable urban spaces and indirect economic impacts, which we suggest may have significant impacts on future urban flood risk. This article is part of the theme issue 'Urban flood resilience'.

A restatement of the natural science evidence concerning catchment-based 'natural' flood management in the UK.

Flooding is a very costly natural hazard in the UK and is expected to increase further under future climate change scenarios. Flood defences are commonly deployed to protect communities and property from flooding, but in recent years flood management policy has looked towards solutions that seek to mitigate flood risk at flood-prone sites through targeted interventions throughout the catchment, sometimes using techniques which involve working with natural processes. This paper describes a project to provide a succinct summary of the natural science evidence base concerning the effectiveness of catchment-based 'natural' flood management in the UK. The evidence summary is designed to be read by an informed but not technically specialist audience. Each evidence statement is placed into one of four categories describing the nature of the underlying information. The evidence summary forms the appendix to this paper and an annotated bibliography is provided in the electronic supplementary material.