Assessing future flood risk and opportunities for adaptation at UK scale Paul Sayers Sayers and Partners (SPL), Associate-Advisor WWF and Reserach Fellow, University of Oxford. Co-authors Matt Horritt, Edmund Penning-Rowsell and Andrew McKenzie BRISBANE, AUSTRALIA | 18 - 20 SEPTEMBER 2017 MANAGED BY

Outline Background Approach Results Conclusions

Background Why assess future flood risks at a national scale

Ten golden rules of strategic flood risk Management (Sayers et al., 2014)

UK Climate Change Act 2008 The UK Climate Change Act requires The Climate Change Committee to undertake a Climate Change Risk Assessment (the CCRA) every 5 years and then produce a policy programme to address those risks The Adaptation Sub-Committee advises on this assessment and scrutinises the implementation of the policy programme The first CCRA was completed in 2012 The second CCRA is due for publication 2017 The evidence provided on future flood risk is the subject this talk

Approach To assessing future flood risk at a UK scale through to the 2080s

An all sources approach: Flood hazards Fluvial Tewksbury, UK July 2007 Coastal West Bay, Dorset, October 2004 Taken by: West Dorset District Council Groundwater Berkshire, March 2014 Taken by: A McKenzie Permeable Superficial Deposits Clearwater (Chalk and other aquifers) Surface water Bristol road, Birmingham, 2000 Taken by: John Blanksby

System descriptors Sources Pathways Receptors Drivers of exogenous change change Climate change Rainfall Short duration(<6hrs) Longer duration Sea level rise Deterioration of defences / levees Population growth and household occupancy Risk = f(chance and consequences) Property Business People Agriculture Critical infrastructure Natural capital System descriptors Extremes rainfall and sea levels Hydrological and hydraulic processes Exposure and social vulnerability Whole system analysis (Future Flood Explorer) Sources Pathways Receptors Excluded here Probability: Formal defences Coastal foreshore management Rural land management Urban surface water management Exposure: Spatial planning Vulnerability: Property level protection Forecasting and warning Endogenous responses change

UK Future Flood Explorer An emulation approach that brings together spatially explicitly data on Flood probability Flood defences

UK Future Flood Explorer An emulation approach that brings together spatially explicitly data on Flood probability Flood defences Receptors

Alterative adaptation scenarios

Results So how do risks change and what impact does alterative levels of adaptation have?

Example results: Change in EAD (£) H++ Future: Low growth 2oC Future: Low growth 4oC Future: Low growth

Example results: EAD (£) through time Expected Annual (direct) Damages (EAD) The UK through time

Some example: EAD by source Expected Annual (direct) Damages (EAD) The UK through time By Source Top: 2oC low growth Bottom:4oC low growth

Example results Summary contribution to risk (2050s) And Ability for adaptation to reduce risk Top: 2oC low growth Bottom:2oC high growth

A focus on vulnerable coastal defences Left: Highly vulnerable defences and temporary inundation extent under a 1:200 year return period tidal surge and a range of assumed values of sea level rise Bottom: Relationship between SLR and length of highly vulnerable defences

The contribution to risk reduction from individual measures as part of a portfolio (Example for Cumbria, Sayers and Horritt, 2016)

Conclusions If we ‘carry on’ as we are how do risks change? Increases in flood risk are projected to occur as early as the 2020s and significantly by 2080s: 50% under 2°C 150% under 4°C The increase varies across the UK; in some regions three times greater than in others. Climate change is the main driver of increased risk, population growth is much less important

Conclusions If we adopt a more ambitious approach to adaptation what is the impact on future flood risk? Enhanced Whole System adaptation can offset all the increase in risk under the 2°C climate change and low population growth projection, or 70% of the increase in risk associated with the 4°C climate change This involves a portfolio of responses to manage probability, exposure and vulnerability

Conclusions And where next for the UK Future Flood Explorer itself.. The FFE is well suited to large scale analysis and exploration of alternative futures Recent extensions to explore issues of social justice in flood risk management in the UK International development and applications, we are currently developing the Awash FFE.

Acknowledgements and references Further detail Sayers et al, Climate Change Risk Assessment 2017: Future flooding report. https://www.theccc.org.uk/publication/sayers-for-the-asc-projections-of-future-flood-risk-in-the-uk/ Funding Primarily provided by NERC via the Committee on Climate Change for the CCRA. The NERC FoRUM (Grant NE/M008851/1) supported the use of the FFE in the validation of the national scale risk analysis for England. Contact Paul Sayers Paul.sayers@sayersandpartners.co.uk Skype: floodsman Telephone: 01865 600039