Do I Need a Flood Risk Assessment for Planning Permission?

If your site sits near a river, the coast or a known surface-water flood path — or simply covers more than a hectare — the planning authority will usually expect a Flood Risk Assessment (FRA) to be submitted with your application. This guide explains, in plain English, when a flood risk assessment for planning permission is actually required, and what one involves.

When is a Flood Risk Assessment required?

Under the National Planning Policy Framework (NPPF) and the Planning Practice Guidance, a site-specific flood risk assessment is normally needed when any of the following apply:

• The site is in Flood Zone 2 or Flood Zone 3 on the Environment Agency flood map.
• The site is in Flood Zone 1 but is 1 hectare or larger.
• The site is in an area with known surface water, groundwater, sewer or reservoir flooding, or within a Critical Drainage Area.
• The proposal is a change of use to a more vulnerable use — for example, turning a commercial unit into housing.
• The local planning authority or lead local flood authority (LLFA) has specifically asked for one.

What if my site is in Flood Zone 1?

Flood Zone 1 is the lowest-probability zone for river and sea flooding, and for most small sites there a full FRA is not required. However, two things still catch people out: sites of a hectare or more need an assessment even in Zone 1, and surface-water (pluvial) flooding is not shown on the main flood zone map at all. Many Zone 1 sites still flood from rainfall runoff, so a drainage strategy or a proportionate FRA can still be requested.

What the planning authority is looking for

An FRA has to show that the development is safe for its lifetime, will not increase flood risk elsewhere, and where possible reduces flood risk overall. In practice that means assessing all sources of flooding, applying the correct climate change allowances, setting appropriate finished floor levels, demonstrating safe access and escape, and setting out how surface water will be managed through sustainable drainage (SuDS).

How to find out quickly — before you spend anything

You can check your site's flood zone on the Environment Agency's "Check the long term flood risk" service using the postcode. But the flood map only tells part of the story, and the vulnerability of your proposed use, the Sequential Test and surface-water risk all affect what the council will expect. The fastest route is to send us the postcode and a line about what you are planning — we will tell you whether an FRA is likely to be required and at what level, usually within a working day.

Read next: Flood Zones 1, 2 and 3 explained, or see our Flood Risk Assessment service.

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