FUTURE-DRAINAGE: Ensemble climate change rainfall estimates for sustainable drainage

The new climate projections from the UK have just been released and as part of this, next year, there will be the release of outputs from a number of very high resolution climate models across the UK. These models are able to represent the daily cycle of rainfall, and rainfall characteristics like intensity, duration and frequency of occurrence, much better than coarser resolution models that have been used previously and can therefore help us to understand how short-duration intense rainfall events and flash floods might change in the future. Here we propose to couple them, for the first time, with new, high-resolution flood models for small rapid response catchments, like Boscastle, or urban areas that suffer from flash floods. Together they will be used to update guidance for urban drainage design and methods for urban surface water flood risk assessment in the UK: priorities identified in the National Flood Resilience Review (2016) and restated in the UK Adaptation Sub-Committee's UK Climate Change Risk Assessment 2017 Synthesis Report: Appendix on Urgency Scoring Tables which identified "Risks of sewer flooding due to heavy rainfall" as an area where "more action is needed to deliver sustainable drainage systems, upgrade sewers where appropriate and tackle drivers increasing surface runoff (e.g. impermeable surfacing in urban areas)." This will include new 'uplifts' that can be applied to design storm events to represent climate change effects on storms and recommendations on the updates of existing methods and tools used to tackle surface water flooding.

FUTURE-DRAINAGE will add to the evidence-base for the UK Climate Change Risk Assessment and the National Adaptation Programme; and is aligned with the UK Government's 25 Year Environment Plan (2018), specifically the goal of reducing risk of harm from environmental hazards and of adapting to climate by improving climate resilience in the UK. The importance of revised rainfall uplifts and new guidance for UK urban drainage design and urban flood resilience is evidenced in the letters of support our project team has solicited from UK water and sewerage companies, the Scottish Environment Protection Agency and informal support from the Environment Agency who considers the work is of particular relevance to applications in surface water management and design of storm water systems. Therefore, FUTURE-DRAINAGE will deliver nationally important research outputs for uptake by government agencies and industrial sectors to improve climate change adaption and resilience in the UK.

Building upon our strong track-record of collaborations with a wide range of stakeholders and project partners in previous NERC-funded Climate Resilience research, we have taken care to work closely with the various communities who will directly benefit from our research in building the Case for Support for this proposal. We will continuously engage with this community throughout the project.

The new UKCP18 ensemble CPM projections together with new, high-resolution flood models developed in SINATRA/TENDERLY by Co-I Liang provide an exciting and timely opportunity to update guidance for urban drainage design and guidance and methods for urban surface water flood risk assessment in the UK: priorities identified in the National Flood Resilience Review (2016) and reiterated in the UK Adaptation Sub-Committee's UK Climate Change Risk
Assessment 2017 Synthesis Report: Appendix on Urgency Scoring Tables (ASC 2016) which identified "In4: Risks of sewer flooding due to heavy rainfall" as an area where "more action needed to deliver sustainable drainage systems, upgrade sewers where appropriate and tackle drivers increasing surface runoff (e.g. impermeable surfacing in urban areas)." In2 and PB5 also cover risks to infrastructure and people from surface flooding (including surface water flooding). FUTURE-DRAINAGE will add to the evidence-base for the UK Climate Change Risk Assessment and the National Adaptation Programme; and is aligned with the UK Government's 25 Year Environment Plan (2018), specifically the goal of reducing risk of harm from environmental hazards and of adapting to climate by improving climate resilience in the UK. The importance of revised rainfall uplifts and new guidance for UK urban drainage design and urban flood resilience is evidenced in the letters of support our project team has solicited from UK water and sewerage companies (WaSCs) and the offer of informal support from the Environment Agency who considers the work is of particular relevance to applications in surface water management and design of storm water systems. Therefore, FUTURE-DRAINAGE will deliver nationally important research outputs for uptake by government agencies and industrial sectors to improve climate change adaption and resilience in the UK.

The main beneficiaries of this work will be the practitioners, regulators and policymakers such as the UK water and sewerage companies (WaSCs), the Environment Agency (EA), Scottish Environment Protection Agency (SEPA), Defra, the Committee for Climate Change, and consultants in the water field. The UK WaSCs have an interest in revised rainfall uplifts to help with their investment planning cycle and have agreed to participate in the project through the reviewing of project reports to ensure benefit / applicability to UK water industry and attendance of the project start-up and final meetings. Government departments and agencies with responsibility for planning, adaptation and mitigation of urban flood risks and flooding from urban drainage systems have a direct interest in the most up-to-date projections from climate models. Providing revised rainfall uplifts from ensemble CPM projections will enable each of these users to better plan for future changes. It will benefit the EA and SEPA who are responsible for managing flood risk, forecasting and warning the public of floods but still have gaps in their understanding of how extremes of rainfall may change; the Department for Environment, Food and Rural Affairs (Defra), with overall policy responsibility for flood and coastal erosion risk in England; the Department for Communities and Local Government (DCLG) with responsibility for coordinating UK resilience to major floods through the co-ordination of regional and local organisations and emergency planning. This work is also likely to inform the next UK Climate Change Risk Assessment and subsequent action through the National Adaptation Programme with the Committee on Climate Change.