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01 · Planning stage · Planning

Flood risk assessment

If your site is in or near a flood zone, or is a larger development anywhere, your council will usually ask for a flood risk assessment before granting planning permission, alongside a drainage strategy showing how surface water will be managed.

DWGuide by Dan Wallis · Updated 4 October 2026

This guide covers the rules in England. See Wales, Scotland and Northern Ireland.

23 flood risk consultantsPlanning
Who needs oneSites in Flood Zones 2 or 3, sites over 1 hectare in Flood Zone 1, or where the council’s checklist flags surface water risk
Who can do itA flood risk or drainage consultant, often a chartered engineer
WhenBefore you submit, so the design can respond to the findings

23 flood risk consultants listed across the UK

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Find flood risk consultants by region

London (6) South East (4) West Midlands (3) Yorkshire and the Humber (4) North West (4) Wales (3) Scotland (3)

National providers (23)

BWB Consulting

Based in Nottingham, Nottinghamshire (also Birmingham, Leeds, London, Manchester) · Covers UK-wide (national coverage from five English offices) Accreditation stated by provider: Not confirmed on site
Own websiteUK-wide
Flood risk assessment
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Create Consulting Engineers

Based in Norwich, Norfolk (also London, Glasgow, Chelmsford, Milton Keynes) · Covers UK-wide (England and Scotland, from five offices) Accreditation stated by provider: Constructionline Silver, CIBSE Low Carbon Consultant, SMAS Worksafe (no CIWEM/ICE confirmed on this page)
Own websiteUK-wide
Flood risk assessment
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Waterco (Waterco Datrys)

Based in Ruthin, Denbighshire, North Wales (also Caernarfon and Mold) · Covers North Wales and North West England, with UK-wide project delivery Accreditation stated by provider: ICE Approved, WIRS accredited, ISOQAR, UVDB (BS8555/CIWEM not confirmed on site)
Own websiteUK-wide
Flood risk assessment
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What it covers

  • The flood zone the site sits in, and the type of flooding it’s at risk from (river, surface water, groundwater)
  • Whether the development will increase flood risk elsewhere, and how that’s mitigated
  • A sustainable drainage strategy (SuDS) showing how surface water will be managed on site
  • Finished floor levels and safe access and escape routes where needed

Sustainable drainage (SuDS)

Most new development now needs to manage surface water sustainably, for example with permeable paving, soakaways, swales or attenuation storage, rather than sending it straight to the sewer. Your drainage strategy usually needs sign-off from the council or the lead local flood authority.

In Wales, Scotland and Northern Ireland

This guide describes the rules in England. Building regulations are devolved, so here is how flood risk assessment works in the rest of the UK.

Wales

Natural Resources Wales maintains its own flood maps, and most new developments need sustainable drainage approved under Wales’s statutory SuDS system.

Scotland

SEPA maintains Scotland’s flood maps. Drainage strategies are assessed against Scottish planning policy and often need Scottish Water’s input.

Northern Ireland

The Rivers Agency maintains Northern Ireland’s flood maps. Drainage strategies are assessed by the council alongside NI Water.

Common questions

How do I know if my site is in a flood zone?

Check the government’s long-term flood risk maps for your postcode. Your consultant will confirm the exact zone as part of the assessment.

Does a small extension need one?

Usually only if the site is in a higher flood zone or the council’s checklist specifically asks for it; most extensions in Flood Zone 1 don’t need a full assessment.

What is SuDS?

Sustainable drainage systems: ways of managing surface water on site, such as permeable paving or soakaways, instead of relying entirely on the sewer network.

Who approves the drainage strategy?

Usually the council or the lead local flood authority, sometimes alongside the water company for sewer connections.

New to the jargon? See our glossary of terms, from air permeability to TrustMark.