Background
In order to ensure that reservoirs are properly maintained and to minimise the possibility of reservoir failure, large reservoirs in England and Wales (capable of holding more that 25,000 cubic metres of water) are regulated under the Reservoirs Act 1975.
This legislation, which is enforced by the Environment Agency, requires reservoirs to be routinely inspected and maintained to an appropriate standard. At present there are approximately two thousand reservoirs in England and Wales covered by the Reservoirs Act.
Provided a reservoir is properly maintained the likelihood of it failing and causing flooding is extremely low. Since the first reservoir legislation was introduced in the 1920s, the UK has not had a single reservoir failure resulting in loss of life.
Current reservoir legislation, which the Flood and Water Management Act enhances, aims to ensure that all reservoirs that pose a safety risk are properly maintained and monitored in order to detect and repair any problems as early as possible. Reservoir flood planning is being undertaken at a Greater Manchester level to ensure that where the flood waters affect more than one local authority area the response can be consistent.
Mapping Project
One of the recommendations in Sir Michael Pitt’s review into the 2007 floods was that the government should produce reservoir flood maps showing the areas that might be at risk from reservoir flooding and should give these maps to local resilience forums (LRF) so they can use them to prepare emergency plans.
In line with this recommendation, reservoir flood mapping of 2,007 reservoirs under the Reservoirs Act was completed in November 2009 and the maps were made available to LRFs shortly thereafter.
Mapping on Environment Agency website
Since completion of the mapping project, the Environment Agency has been working towards adapting the existing ‘What’s In Your Backyard’ facility on its website to allow members of the public to view a map showing whether any location in England or Wales is in an area that could be at risk of reservoir flooding.
Development of this is now complete – the link to the reservoir flooding pages can be accessed from the Environment Agency website (external link).
The reservoir flood maps available on the Environment Agency website are ‘outline’ maps, meaning that they show only the areas that might be flooded in a realistic worst case reservoir failure scenario. (This means that the extent of the flooding shown is the worst that could realistically happen). In fact, if reservoir flooding did occur it would most likely be much less severe than the worst case scenario.
The reservoir flood maps do not give any indication of the likelihood of flooding occurring, unlike the maps for river and coastal flooding which are also available on the Environment Agency website.
The Environment Agency’s website also contains more detailed information on reservoir safety and reservoir flooding, including a list of frequently asked questions covering areas such as: what to do in an emergency, further information on reservoir legislation, and where to go for further advice.
A link to the reservoir flooding pages can be accessed from the Environment Agency website (external link).
