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Water: Maps

Volume 493: debated on Tuesday 2 June 2009

To ask the Secretary of State for Environment, Food and Rural Affairs what assessment he has made of the accuracy of the Environment Agency's surface water mapping; and whether the accuracy of the mapping has been subject to independent verification. (277011)

The Environment Agency has confirmed that the accuracy of the surface water mapping was independently assessed, although the information currently available to do this is limited. The maps of Areas Susceptible to Surface Water were compared with those of the 15 Integrated Urban Drainage pilot projects and models already held by the independent consultants.

The information on the maps is still under development and is currently only considered suitable for emergency planning purposes. The maps give an indication of the broad areas likely to be susceptible to surface water flooding based upon an extreme summer rainfall event with no drainage systems working. The information is not sufficiently accurate to use for individual properties as the current version excludes, for example, the impact of buildings and kerb heights on surface water flows, which at the local level can be significant. There will be properties at risk from surface water flooding that will not be included within the outline areas on the maps, and possibly other individual properties within the areas outlined that are not at risk because of particular local features that the mapping process did not reflect.