Key to understanding the Flood Map for Planning (rivers and the sea)
The map and associated information is intended for guidance, and cannot provide details for individual properties.
A floodplain is the area that would naturally be affected by flooding if a river rises above its banks, or high tides and stormy seas cause flooding in coastal areas.
There are two different kinds of area shown on the Flood Map for Planning 9rivers and the sea. They can be described as follows:
Dark blue shows the area that could be affected by flooding, either from rivers or the sea, if there were no flood defences. This area could be flooded:
- from the sea by a flood that has a 0.5 per cent (1 in 200) or greater chance of happening each year;
- or from a river by a flood that has a 1 per cent (1 in 100) or greater chance of happening each year.
(For planning and development purposes, this is the same as Flood Zone 3, in England only.)
- Light blue shows the additional extent of an extreme flood from rivers or the sea. These outlying areas are likely to be affected by a major flood, with up to a 0.1 per cent (1 in 1000) chance of occurring each year.
(For planning and development purposes, this is the same as Flood Zone 2, in England only.)
These two colours show the extent of the natural floodplain if there were no flood defences or certain other manmade structures and channel improvements.
- Where there is no blue shading, this shows the area where flooding from rivers and the sea is very unlikely. There is less than a 0.1 per cent (1 in 1000) chance of flooding occurring each year. The majority of England and Wales falls within this area. (For planning and development purposes, this is the same as Flood Zone 1, in England only.)
2. Flood Defences
The purple line shows all flood defences built in the last five years to protect against river floods with a 1per cent (1 in 100) chance of happening each year, or floods from the sea with a 0.5 per cent (1 in 200) chance of happening each year, together with some, but not all, older defences and defences which protect against smaller floods. Flood defences that are not yet shown, and the areas that benefit from them, will be gradually added.
Hatched areas benefit from the flood defences shown, in the event of a river flood with a 1 per cent (1 in 100) chance of happening each year, or a flood from the sea with a 0.5 per cent (1 in 200) chance of happening each year. If the defences were not there, these areas would be flooded.
Flood defences do not completely remove the chance of flooding, however, and can be overtopped or fail in extreme weather conditions.
For information on flood defences which are not yet shown on the map, contact your local Environment Agency Office.
3. Main Rivers
The blue line shows the main rivers, these are usually larger streams and rivers.
Our powers to carry out flood defence work apply to main rivers only. In England, DEFRA decides which are main rivers. The Welsh Government does this in Wales.
4. Risk of Flooding from Rivers and the Sea map
This map shows our assessment of the likelihood of flooding from rivers and the sea at any location is based on the presence and effect of all flood defences, predicted flood levels, and ground levels.
We describe the chance of flooding in one of four categories:
- High - greater than to equal to 1 in 30 (3.3%) chance in any given year
- Medium - less than 1 in 30 (3.3%) but greater than or equal to 1 in 100 (1%) chance in any given year
- Low - less than 1 in 100 (1%) but greater than or equal to 1 in 1,000 (0.1%) chance in any given year
- Very Low - less than 1 in 1,000 (0.1%) chance in any given year
Go to risk of Flooding from Rivers and the Sea map
5. Flood Warning
Flood warning schemes have been set up for a number of areas that are considered to be at particular risk from flooding. These areas are called Flood Warning Areas. Within these areas, we can warn residents in advance when flooding may be likely and how severe the flooding could be. We also publish a number of flood warnings that are in force on this site.