National Flood Resilience Review September 2016 Contents Ministerial foreword .................................................................................................... 1 Executive Summary .................................................................................................... 2 1 Generating extreme flood scenarios .................................................................... 6 1.1 Extreme rainfall scenarios ............................................................................. 6 1.2 Extreme tidal scenarios ................................................................................. 8 1.3 Modelling extreme floods and river flows ....................................................... 9 1.4 Scientific advice ........................................................................................... 11 2 Identifying key local infrastructure at risk ........................................................... 14 2.1 Why focus on infrastructure? ....................................................................... 14 2.2 Key local infrastructure at risk in extreme flood scenarios ........................... 15 2.3 Existing and planned permanent defences .................................................. 17 3 Assessing the potential for temporary defences to protect key local infrastructure .......................................................................................................................... 18 3.1 Types and general use of temporary defences ........................................... 18 3.2 Pilot study to assess the potential use of temporary defences .................... 19 4 Next steps ......................................................................................................... 22 4.1 Improving the resilience of local infrastructure ............................................ 22 4.2 Improving incident response ........................................................................ 23 4.3 Pilot for innovative flood defence and urban development in the Core Cities .................................................................................................................... 24 4.4 Rolling programme of long-term modelling improvements .......................... 26 4.5 Environment Agency flood risk communication ........................................... 27 4.6 Surface water flooding ................................................................................. 27 4.7 Long term (post-2021) strategy ................................................................... 28 Annexes.................................................................................................................... 30 Annex 1 - Membership of the National Flood Resilience Review Group ............... 30 Annex 2 - Generating plausible extreme rainfall scenarios for England and Wales .............................................................................................................................. 31 Annex 3 – Modelling for flood risk management ................................................... 46 Annex 4 - Case studies ......................................................................................... 55 Annex 5 - Membership of the Scientific Advisory Group ....................................... 82 Annex 6 - Principles and advice to inform communicating about flood risk ........... 85 Annex 7 - Advice on longer term improvements to modelling extreme flooding .... 90 Annex 8 - Temporary defences ............................................................................. 93 Annex 9 - Temporary defences pilot ..................................................................... 96 Annex 10 - Comparison of international approaches to flood resilience ............... 98 Ministerial foreword Last winter we saw the devastating impact of record rainfall and extreme flood events across wide areas of the country. The Government took swift action to provide direct support to those affected and make sure that communities could get back on their feet as soon as possible. We also set up this review, to assess how the country can be better protected from future flooding and extreme weather events. Although the events we saw last winter are rare, we must recognise that extreme weather and flooding events do happen and that we need to be well equipped to respond. The stress testing of our modelling and flood risk maps carried out as part of this review has provided reassurance that we know the areas of the country which are at risk of flooding. Our next task is to make sure we improve how we let people know where they could be at risk and encourage them to take action. Last winter we saw how disruptive flooding can be for homes and businesses, as well as for key local infrastructure. As part of this review we have secured commitments from the water and telecommunications industries to make their infrastructure more resilient. In addition, this year the Environment Agency will be able to deploy four times more temporary barriers to protect our communities than last winter. As these plans are completed, we are confident that our communities will be better protected. They can have confidence that the essential services they rely on will be even more resilient to the kind of extreme weather we saw last December. Rt Hon Ben Gummer Rt Hon Andrea Leadsom Minister for the Cabinet Office and Secretary of State for Department of Paymaster General Environment, Food and Rural Affairs 1 Executive Summary Over recent years the UK has been hit by a number of extreme flood events, in Somerset, Cumbria, Yorkshire and elsewhere. Record rainfall and river levels have led to widespread floods severely affecting cities and communities, bringing misery to the lives of thousands and seriously disrupting businesses and livelihoods. Communities have lost power, water and telecoms during the flooding, and have then had to deal with the lengthy process of recovery. We need to recognise that there is a non-negligible chance that we will see further events of a similar, or maybe even greater, scale over the next decade. The Government has already taken action to improve our protection from and resilience to flooding. We are spending £2.3 billion over the next six years from 2015- 2021 to strengthen the country’s flood and coastal defences, better protecting 300,000 homes. We are prepared to respond swiftly and effectively to events as and when they happen, and to support communities in the recovery phase. Overseen by a Ministerial Recovery Group, we have put in place a recovery package for homes, businesses and farms in those areas of Northern England affected by last winter’s floods to help get communities back on their feet and to strengthen defences in places such as Leeds, York, the Calder Valley and Cumbria. Flood Re has now been established to ensure that households can continue to obtain flood insurance at affordable cost. But, in the light of the severity of recent events, and the risk that these or similar events will occur again, it is appropriate to reconsider our approaches to assessing flood risk, to reducing the likelihood of flooding, and to making our nation as resilient as possible to flooding. One important area for improvement is better management of rainfall in the natural environment. Water is a precious resource that at many times and in many places is in increasingly short supply. There are obvious benefits to managing water in a way that reduces both flood risk and water stress, and that delivers wider environmental benefits, by slowing the flow of water from the land into our rivers and smoothing the flow of the rivers themselves. The Government’s future 25 year plan for the environment will aim to achieve these effects by managing whole river catchments intelligently, developing sophisticated modelling to work out what can be done in each part of the catchment to minimise flooding. A ‘pioneer’ pilot project in Cumbria will test and demonstrate the power of this approach across the different river catchments there. 2 The reduction in current flood risk that could be achieved through the future 25 year plan for the environment will complement the work on long term risks caused by climate change, which the Adaptation Sub-Committee of the Climate Change Committee has been considering. Integrated catchment management will not, however, deliver flood risk reductions overnight. The magnitude of events in recent years means that it is important to reassure ourselves that we understand the scale of risk that the country is currently facing from river and coastal flooding and to take more immediate steps to improve the resilience of the country to such flooding. We set up the National Flood Resilience Review to look at these questions, chaired by the Chancellor of the Duchy of Lancaster and overseen by a cross-government National Flood Resilience Review Group (see Annex 1 for the group’s membership). This report explains how we have been conducting the review and sets out our findings. Our first programme of work has been to improve our understanding of the fluvial and coastal flood risk in England. As a result of recent events, we have become clear that describing flood risk in traditional terms such as a ‘1% chance of flooding’ or ‘1 in a 100 year risk’ is not helpful because it is so likely to be misinterpreted. These terms describe the flood risk at a specific location. They do not describe the chance of one of these events happening somewhere in the country or region in