Flooding – Reservoirs
It is now possible to access maps on the Environment Agency
Web site by clicking here
This will show you whether your property is in
an area possibly affected by flooding if a reservoir is
breached.
Reservoirs are artificially created ponds or
lakes that are usually formed by building a wall, known as a dam,
across a river. If one of these dams failed then water could escape
from the reservoir, resulting in land or properties being flooded.
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.
However, in the very unlikely event of a dam collapse, a large
volume of water could be released, quickly flooding a large area
and possibly causing significant property damage or even loss of
life. Such a scenario is extremely unlikely to occur and reservoirs
in the UK have an excellent safety record. Since the first
reservoir legislation was introduced in the 1920s, the UK has not
had a single reservoir failure resulting in loss of life.
Although reservoir flooding is unlikely, each
year there are a small number of incidents (fourteen recorded
between 2004 and 2008) that are deemed serious enough to require
emergency drawdown (emptying) of the reservoir, emergency works to
take place on the reservoir, and/or evacuation of people in the
potential path of flooding. One of the most high profile of these
incidents was in the summer of 2007 at the Ulley reservoir in
Rotherham. In this case extreme rainfall caused damage to the dam
and the risk of reservoir flooding led to a decision to evacuate
around 1,000 people near the reservoir and to close main roads
(including the M1). This highlighted the risk to communities living
in reservoir flood zones and prompted Sir Michael Pitt, in his
review into the 2007 floods, to recommend that the government takes
measures to improve reservoir emergency preparedness.
Part of Sir Michael’s recommendation 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. 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 facility is now complete
and can be accessed via the Environment Agency
website.
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
actuality, if reservoir flooding did occur it would most likely be
much less severe than the worst case scenario. However, maps
showing a realistic worst case scenario are useful to emergency
planners who need to know the areas that might need to be evacuated
and where it is safe for people to go to.
The maps on the Environment Agency website do
not give any information about the depth or speed of the flood
waters or the length of time it would take for the flood waters to
reach any location. Even in a worst case scenario many areas shown
as being at risk of reservoir flooding would be expected to receive
no more than one or two centimetres of flood water. Emergency
planners do have access to maps containing additional information.
However, due to the sensitive nature of the information from a
national security perspective, this information is not publicly
available.
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. Reservoir regulation ensures that these
reservoirs are stringently inspected and supervised by qualified
civil engineers and that any required maintenance or upgrade works
are carried out quickly. This helps ensure that the likelihood of
one of them failing remains extremely low.
Most reservoirs in the UK have been there for
over a hundred years without any problems. Many communities have
therefore been living with the very small risk of reservoir
flooding for many years and those communities close to reservoirs
have always been aware that a risk existed. Nothing has changed,
and the risk of reservoir flooding has not increased. Reservoir
legislation and regulation help us ensure that these reservoirs
remain safe, and the reservoir flood maps we now have available to
us allow us to better estimate the areas potentially at risk and to
put in place emergency plans, so we are prepared to respond should
reservoir flooding occur.
The Environment Agency’s website 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. The link to the
reservoir flooding pages will be available from this page:
www.environment-agency.gov.uk/homeandleisure/floods/31650.aspx
The Northumbria Local Resilience Forum has no
reservoirs in its area identified as high risk and is currently
developing a generic Plan for multi agency response in the unlikely
event that any of the designated reservoirs in Northumbria
(Northumberland and Tyne and Wear) should breach.
If you have any questions about your specific
locality you can either use the enquiry facility on the Environment
Agency website (above) or contact your local authority using the
link below:-
Gateshead
Council
janetkirton@gateshead.gov.uk
Newcastle City
Council
resilience@newcastle.gov.uk
North Tyneside
Council
Jonathan.Hutchinson@northtyneside.gov.uk
Northumberland County
Council eplan@northumberland.gov.uk
South Tyneside
Council
james.elliott@southtyneside.gov.uk
Sunderland City
Council
barryfrost@sunderland.gov.uk
