Developing a Site in a Flood Risk Area

Flood Risk

Developing a Site in a Flood Risk Area

Flood Risk

Large regions of the UK are identified by flood mapping as being vulnerable to flooding from rivers, the sea, and surface water. The Environment Agency now state this is 1 in every 4 properties. There are formal lines of defence in many places, such as flood embankments, levees, walls, and storage ponds, most of which are managed by the Environment Agency (in England). Because of their industrial past, many major towns and cities are situated close to rivers and coastlines, making flooding an unavoidable risk that needs to be constantly managed.

One city that heavily relies on the extensive flood defence system along the River Thames corridor to safeguard it is London. If you were to look at the city’s flood maps, you would see that a number of London’s most densely populated regions fall within designated flood zones. Considering this, it begs the question of how, given the presence of this risk, so many new construction projects continue to be initiated within the nation’s capital.

The lack of suitable sites, the desire for housing, and the expanding population can all contribute to the answer to this issue. Your local planning authority (LPA) will frequently ultimately decide whether a site is appropriate for development when flood risk is taken into account. Prior to making a final choice, the LPA frequently seek advice from statutory consultees like the Internal Drainage Boards (IDBs) and the Environment Agency (in England).

You should first request pre-development guidance from the LPA if you are thinking about developing a site that has been designated as being at risk of flooding. A flood risk specialist should then be given this guidance so that they can give you a realistic assessment of whether the development would be feasible in the LPA’s eyes. The most crucial stage is to use a flood risk expert to sense-check your development goals, ensuring that pursuing obtaining planning permission for a development is worthwhile of both your time and money.

When a site is first determined to be at danger for flooding, several scenarios may occur. The best and easiest situation is one in which your chosen flood risk expert is able to offer reliable proof that your site actually faces less risk than what is indicated by flood zone mapping. Comparing site levels with matching local flood levels can result in this kind of scenario.

In cases where flood danger cannot be completely eliminated, the LPA may ask for evidence of sequential testing. This method evaluates whether there are any nearby development sites of a comparable nature that might be less likely to flood. The developer must then conduct an appropriately thorough Exception Test when there are few or no alternatives for moving a development elsewhere.

Exception Test in Flood Risk

Any additional factors that would need to be included in the plan would be described by the Exception Test. This would entail reducing any danger to individuals nearby and elsewhere for the duration of the development. Where there is a high likelihood of flooding and/or a possible depth of flooding, a warning should be issued at this time. In some cases, the risk would directly conflict with regional and governmental planning directives, making it impossible and morally wrong to give permission. A diligent flood risk expert would let you know about this as soon as possible so you could consider any potential financial risks.

If a building successfully passes the Exception Test, you might then need to show the LPA that any displaced flood water is still contained on your property. This is done to prevent any damaging inundation in other areas. This is commonly referred to as compensatory storage.

Fortunately, not all developments are required to go through this process in order to receive planning, but it must be noted that diligently managing this risk would prevent additional problems in the future.


Mortgage lenders are now being much more cautious when making loans for homes in flood-prone areas, so they might require proof of how a property can handle any remaining risk. Additionally, property insurers evaluate a location for the risk of flooding, which means that insurance may be rejected if they determine that the risk is too great for their needs.

An experienced flood risk professional would be able to assist you in overcoming the challenges of flood risk and help you maximise your development aspirations at each stage of the procedure outlined above.

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