(This post is part of an occasional series. It is on how the UK planning system works. These posts are not by planning experts but rather by interested amateurs. They come as-is. Any corrections welcome)
Every council has to produce a Strategic Flood Risk Assessment. It produces this document in conjunction with the Environment Agency. The Environment Agency divides locality into Flood Risk Zones.
As an example: Here is the Dorset Council Flood Risk Management Strategy.
Note:The existing document for Dorset Council appears to be a legacy document from Dorset County council that has been inherited by the new authority.
Here is the link: Flood Risk Management Strategy for Dorset
Unfortunately both of these government sites are quite poorly presented and make for difficult reading.
Flood risk assessment is one of the the most important aspects of any new development. It is also in some cases important for smaller developments too. Or even extensions to existing properties. Is is worth knowing that Councils are always supposed to adopt a cautionary approach when considering developments in potential flood areas.
It is one of the biggest potential problems faced by developers and can be very difficult to override, even when the developer is armed with expensive lawyers.
The Strategic Flood Risk Assessment does not deal with individual sites. However it does cover the overall ethos that the council aspires to meet regarding flood risk and development site allocation. But it has been known for councils to attempt to ditch their own guidelines. Or sometimes work round them if it suites their agenda.
Flood Risk Zones
Areas are analyzed by the Environment Agency and then divided into one of three Flood Risk Zones (the third and most prone to flooding is subdivided into two 3A and 3B)
Flood Zone One:
This is the safest and least likely to flood. The odds of flooding are less than one in a thousand. This is what all developers want to get their land categorised as.
Flood Zone Two:
The flood risk on a category two site is between 1:100 and 1:1000. A developer would regard getting development land categorised as category 2 as a serious blow to development potential. They would often be prepared to spend a lot of money to try and overturn the categorisation and get it re-categorised to Category One.
Flood Zone 3 is divided into two levels
Flood Zone 3A:
The the risk of flooding here is 1:100 or worse. The land in this category is described as being affected by a flood plain. Unless Flood Zone 1/2 land is seriously constrained it is unlikely that Zone 3A land will be allowed major development and small development will be difficult. Even so there are a lot of houses that already exist in flood zones 3A and 3B. If modifications (aka extensions) are planned they usually need to have an individual assessment by the Environment agency and then have to abide by the result.
Flood Zone 3B:
The category is liable to flood and forms part of the flood plain. The risk of flooding is worse than 1:30. It is unlikely that this category will get large scale development in almost all circumstances. Even these days it is unlikely that even large arrogant developers will try their luck with a 3B site.
Most councils now only consider development on Flood Zone 1. There is a caveat though. They may allow development on Flood Zone 2 or (unusually) Flood Zone 3A if, (and only if) there is no suitable Flood Zone 1 land available.
Councils must perform a “sequential test” on any land allocation if it falls below Flood Zone 2. Often in the local plans this is actually set at Flood Zone 1, so if any potential development is going to be on less than a Flood Zone 1 site then it has to be proved that there is no suitable Flood Zone 1 land capable of supporting the same development.
So on the face of it, if the land is classified as other than Flood Zone 1 then any large development is going to have problems.
The first port of call to find out the flood status of any property is the Land Registry. Some years ago The Land Registry had started selling the flood status of land along with the deeds. When the author used it some years back it proved to be arbitrary and sometimes just plain wrong. Hopefully it is now improved.
If you are concerned about a proposed development and its potential affect on the surrounding area then the local Flood Zone status and local government policy should be thoroughly investigated.