Why do I need a Flood Risk Assessment in a Flood Zone 1?

A Flood Risk Assessment is normally required for any planning application where the site of the proposed development is located within Flood Zones 2 or 3 as defined by the Environment Agency. However, GeoSmart is often get asked by clients why the local Council/Environment Agency have asked for a Flood Risk Assessment when the proposed development is located within Flood Zone 1.

Areas classified as Flood Zone 1 are those that have less than a 0.1% chance of flooding. A Flood Risk Assessment is mandatory for sites of 1 hectare or greater in Flood Zone 1.There are also sites which are less than 1 hectare within Flood Zone 1 which need a Flood Risk Assessment, including sites which have critical drainage problems, as notified to the local planning authority by the Environment Agency. Critical Drainage Areas (CDA) are specific areas within Flood Zone 1 where man made drainage infrastructure has been identified as at critical risk of failure, resulting in runoff causing problems downstream. Flood Risk Assessments are not necessarily just an area where flooding problems may occur.

You may also need to do a Flood Risk Assessment in Flood Zone 1, if your development could be subject to other sources of flooding (for example surface water drains or reservoirs) or a change of use in development type to a more vulnerable class, such as commercial to residential, could also lead to a Flood Risk Assessment being required.

What if my Site is wholly or partially within a Flood Zone 2 or 3?

It should be noted that a Flood Risk Assessment catered to Sites within Flood Zone 1 will not be suitable for a Site within Flood Zones 2 or 3. If the Site is in a higher flood risk zone, the Council and Environment Agency will request that flood model data from the Environment Agency is included in the Flood Risk Assessment. This will be the case even if part of the Site red line planning boundary is within a Flood Zone 2 or 3 or if the proposed development will be located in the lower risk area (Flood Zone 1) of the Site boundary.

How do I find out which Flood Zone my Site is in? 

If your Site is in England, it will be located in a Flood Zone 1-3 as defined by the Environment Agency’s Flood map for planning. Find out which Flood Zone your site is located in, enter your postcode into the Environment Agency Flood Map to find out.

If your Site is in Wales, Natural Resources Wales (NRW) have their own Flood Zones. Three development advice zones (A, B, C) are described on their maps, which are attributed to different planning actions. Zones A and B are areas of generally low risk. Zone C represents the extreme flood outline, and is further subdivided into two zones, C1 and C2.

Zone C1: described as “areas of the floodplain which are developed and served by significant infrastructure, including flood defences.

Zone C2: described as “areas of the floodplain without significant flood defence infrastructure.

Essentially, if the Site is in a Flood Zone C1 or C2, this is the equivalent of the EA’s Flood Zone 3.

If your Site is in Scotland, the Scottish Environmental Protection Agency (SEPA) rate flood risk by likelihood of flooding from Rivers, Surface Water and Coastal Flooding. These are divided into high, medium and low risk zones.

Where can I purchase a Flood Risk Assessment?

GeoSmart can provide such a Flood Risk Assessment, suitable for Sites within a Flood Zone 1. The assessment includes flooding from all sources, in a clear report of flood hazards which may be present.

Tags: flood risk, flood risk assessment, flood zone 1, flood zones