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New study assesses impact of climate change on flood risk in the UK

New study assesses impact of climate change on flood risk in the UK. Recommends a wider uptake of sustainable drainage systems (SuDS) and further investment in flood defences to offset the likely impact of climate change

The Committee on Climate Change has published the findings of four research projects which were commissioned by its Adaptation Sub-Committee. The research will feed into the UK Government’s climate change risk assessment in 2017. Two of the research projects were concerned with preparing the UK for two water extremes: flood and drought.

David Style from the Committee on Climate Change says “Both sets of water-related projections address uncertainty by considering a range of possible scenarios, based on differing levels of climate change, population growth, and adaptation effort.”

The research on flood risk was carried out by Sayers and Partners. The study predicts that by the 2050s nearly half a million more homes will be at a significant risk of flooding (at a 1 in 75 or greater chance of flooding in any given year). David Style says: “This takes into account current approaches to flood risk management and assumes these continue. In more extreme climate change scenarios, if global temperatures increase by 4°C rather than 2°C by the 2080s, and if population growth is high, then this figure increases to more than a million additional homes.”

To fully offset the increase in risk expected under a 2°C climate change projection, the study says that a much wider uptake of sustainable drainage systems (SuDS) and property-level protection measures, as well as additional investment in maintaining and enhancing flood defences, would be needed. David Style says that under a 4°C climate change projection, not even this enhanced level of adaptation would be sufficient to completely offset the increase in risk.

The research also considers the consequences should existing coastal defences fail as sea levels rise. “A 0.5 to 1 metre rise in sea levels,” says David Style, “which is plausible by the end of the century, would make around 200km of coastal defences (20%) highly vulnerable to failure. This would lead to 200,000 hectares of land and 400,000 properties being at risk of a 1-in-200 year tidal surge, as experienced in January 1953 and December 2013. Localities with the highest number of properties at risk in this scenario include Cleethorpes, Fleetwood, Weston-Super-Mare, Eastbourne, Burnham-on-Sea, Bognor Regis, Worthing, Bridgewater and New Romney.”

The second research project, carried out by HR Wallingford, looks at the impact of climate change and population growth on water resources. The research predicts that, as global temperatures increase and the UK population grows, increases in demand for water will be accompanied by decreases in water availability due to climate change. Supply-demand deficits, with demand outstripping supply, are projected to be widespread by the 2050s.

“Overall,” says David Style, “further adaptation is needed to offset the projected increases in risk from both flooding and water scarcity even under a 2°C temperature rise scenario.” He points out that water-related risks (flood and drought) are considered in isolation, but there are clearly benefits in addressing them together in some parts of the country: “For example, approaches to natural flood management, such as peatland restoration, can help store rainwater in upland areas and help recharge aquifers. SuDS in urban areas slow down and capture rainwater, allowing it to filter into the ground, rather than add to river levels or sewer overspills and be flushed out to sea.”

On flood risk, he says the key message from the study is clear: “Avoiding significantly more flood damage means keeping global increases in temperature to no more than 2°C, while also investing in and delivering stronger flood risk management policies and plans across the country.”

For further details of the research, see the Climate Change Committee website.

Notes

1. The Adaptation Sub-Committee of the Committee on Climate Change was established under the 2008 Climate Change Act to provide the UK Government with independent, evidence-based advice on preparing for climate change. The Committee consists of experts from the fields of science, engineering, economics, urban planning and public health.
2. GeoSmart has a new range of Sustainable Drainage System (SuDS) Reports. For further information on our flood risk assessments and drainage reports, see our Reports page or give us a call on 01743 298 100.