PLEASE NOTE: This dataset has now been retired and is superseded by a new dataset called: Reduction in Risk of Flooding from Rivers and Sea due to Defences. The Areas Benefiting from Defences dataset was assessed as no longer sufficiently meeting the needs of our customers and partners and was last updated on 02/11/2022.
The Flood Map for Planning (Rivers and Sea) includes several layers of information one of which is areas benefiting from defences. This dataset shows those areas that benefit from the presence of defences in a 1 in 100 (1%) chance of flooding each year from rivers; or 1 in 200 (0.5 %) chance of flooding each year from the sea. If the defences were not there, these areas would flood in a 1 in 100 (1%)/ 1 in 200 (0.5 %) or larger flooding incident. Note that we do not show all areas that benefit from all flood defences.
Some defences are designed to protect against a smaller flood with a higher chance of occurring in any year, for example a flood defence which protects against a 1 in 30 chance of flooding in any year. Such a defence may be overtopped in a flood with a 1 in 100 (1%)/ 1 in 200 (0.5%) chance of occurring in any year, but the defence may still reduce the affected area or delay (rather than prevent) a flood, giving people more time to act and therefore reduce the consequences of flooding.
We do not always map areas that benefit from defences that offer a lower standard of protection.
Other defences are designed to withstand a larger flood with a smaller chance of occurring in any year. In this case, we show only the area that would have been affected in a flood with a 1 in 100 (1%)/ 1 in 200 (0.5%) chance of occurring in any year, even though further areas would benefit in the event of more severe flooding for example in a 1 in 1000 (0.1%) flood.
The rivers and sea criteria 1 in 100 (1%)/ 1 in 200 (0.5%) chance of occurring in any year aligns with Flood Zone 3 as described in the Planning Practice Guidance.
In mapping areas benefiting from defences, we assume that flood defences and other operating structures act perfectly and give the same level of protection as when our assessment of the area was made.
Please download our related dataset Risk of Flooding from Rivers and Sea to understand the flood risk that remains in locations where the location of flood defences and their condition have been included in the modelling.
Attribution Statement: © Environment Agency copyright and/or database right 2018. All rights reserved.Some features of this map are based on digital spatial data from the Centre for Ecology & Hydrology, © NERC (CEH) © Crown copyright and database rights 2018 Ordnance Survey 100024198