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The Requirements of Flood Risk Assessments

A Flood Risk Assessment is normally required for any planning application where the site of the development is in Flood Zones 2 or 3 as defined by the Environment Agency. Many clients ask us why Flood Zone 1 is required by the Environment Agency/Local Council.
Flood Zone 1 is an area with a lower than 0.1% chance for flooding. Flood Zone 1 sites with the minimum of one hectare must have an Flood Risk Assessment. Sites that are less than 1 hectare in Flood Zone 1 also require the completion of a Flood Risk Assessment. These sites include sites with significant drainage problems, and are required to be reported to the local planning authority through 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 failing, which could result in the runoff of water causing issues downstream. Flood Risk Assessments don’t just tackle flooding issues.

Flood Zone 1 may also require an Flood Risk Assessment. This is if your development may be affected by flooding from other sources (surface water drains or reservoirs), or a change in development’s use to a higher risk class like commercial or residential.

What if my Site is completely or in part within the boundaries of a Flood Zone 2 or 3?

A Flood Risk Assessment that is tailored to sites within Flood Zone 1 won’t be suitable for sites that are in Flood Zone 2 or 3. If the Site is located in a more risk zone for flooding it is expected that the Council and Environment Agency will demand that data from the flood model provided by the Environment Agency is included in the Flood Risk Assessment. This will be the case regardless of whether a portion of the Site red line planning boundary falls within the boundaries of a Flood Zone 2 or 3 or if the proposed development is located within the lower risk zone (Flood Zone 1) of the Site boundary.

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

Your site will fall into Flood Zone 1 to 3 If it is located in England. This Flood Zone was established by the Environment Agency Flood map. To determine in which Flood Zone is your site is located, just type in your postcode in Flood Map by Environment Agency.

If your Site is in Wales, Natural Resources Wales (NRW) has its own Flood Zones. The maps display three development advice zones (A-B C, A and C) and could be linked to various plans. Zones B and A are zones with a low risk. Zone C is the highest floodline and is further subdivided into two zones, C1 and C2.

Zone C1 is described as “areas of the floodplains that are built and are served by an extensive infrastructure, such as flood defences.

Zone C2 can be described as “area of floodplain without any significant flood defence infrastructure.”

Essentially, if the Site is in the Flood Zone C1 or C2 it is an equivalent to the EA’s Flood Zone 3.

The Scottish Environmental Protection Agency (SEPA) located in Scotland assesses flood risk in relation to the risk of flooding from surface waters, rivers as well as coastal flooding. The zones are classified into high, medium, and low-risk zones.

Where can I purchase an Flood Risk Assessment?

This Flood Risk Assessment is available for all sites in the Flood Zone 1. The assessment considers flooding from all sources in a detailed description of the flood risks that could be present.