One in Four British Homes at Flood Risk, Says RMS

London –  June 24, 2008 – As many as one in four homes in Britain is at risk of flooding caused by excessive rainfall and rivers overflowing, according to Risk Management Solutions (RMS), the world’s leading catastrophe modeling experts. Its spatial analysis of British properties – using high-resolution satellite imagery – shows that approximately £600 billion of residential building value is exposed to flood risk*.  Yet, many people are unaware their home is at risk because the government’s flood maps, provided by the Environment Agency, do not include the probability of drains being overwhelmed by extreme rainfall, which accounted for some two-thirds of the damage caused by last year’s floods.

“The Environment Agency’s maps only tell part the story about flood risk in Britain,” said Dr. Alice Stuart-Menteth, European flood model manager at RMS. “When you take into account surface water flooding, the picture becomes more alarming because thousands more homes are exposed than the government suggests. Last summer’s events clearly demonstrate that flooding from heavy rainfall in areas with inadequate drainage or from minor streams can have devastating consequences.”

Hull, one of the most badly affected areas from the June 25, 2007 flood, was classified as just being at risk of tidal flooding, despite being exposed to surface water flooding.  “People need to know the likelihood of their home being affected by all types of flooding. They can then invest in making their property more resilient, like through raising the floor or waterproofing the electrics, or at least react quickly when a flood does occur,” commented Dr. Stuart-Menteth. 

Floods Affecting Multiple Areas
Using the Environment Agency’s maps, it is currently not possible to assess how one catastrophic flood could simultaneously impact different locations, which has consequences for emergency response planners, owners of major utility companies, and insurers. Disaster plans developed on a local scale could be severely stretched if a flood affects a number of areas.

“Multiple locations can be immersed during a catastrophic flood, which puts pressure on emergency response teams.  Last year, an electricity blackout which could have affected some 600,000 homes over several days was only narrowly avoided in Gloucestershire as the flood water was pumped out in time,” commented Dr. Stuart-Menteth. “The loss of two or more electricity stations across the country at the same time could create an evacuation situation similar to New Orleans after Hurricane Katrina. Disaster plans need to take account of a range of possible scenarios, so if people have to be evacuated they can be accommodated away from the high-risk areas.”

She added: “If water and electricity are cut off during a flood, the buck often stops with insurers who have to pay some part of these failings, for example through business interruption costs or paying for temporary accommodation. Unless they are aware of these potential scenarios, they could face an unexpected deluge of claims after an event.”

RMS has submitted a response to Sir Michael Pitt’s review of flood risk in the U.K., highlighting the need for a more comprehensive view of flood risk and recommending that the government and its agencies work with the insurance industry to devise mutually beneficial strategies for dealing with flood risk.

*Note to Editors

The RMS analysis of flood risk is based on calculating the number of residential homes within the 2008 RMS 1000-year Inland Flood risk zones compared to the total number of homes in Britain.  The flood risk map identifies areas at risk from all sources of precipitation-driven flooding including flooding from major and minor rivers and surface water flow.  The 1000-year flood risk map identifies areas that would be at risk under very extreme rainfall and flooding.  The RMS UK Inland flood model, first released in 2001, will be updated this summer.