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We’re technical experts in the complex and ever-changing world of civil and structural engineering design and technical approval.

Do I need a Flood Risk Assessment and how much does it cost?

Our answer is based on the Link team’s collective experience, which includes involvement in hundreds of projects of varying scales from inception through to construction, many involving the assessment of flood risk.

We are often asked to quote for and complete a site-specific Flood Risk Assessment (FRA) to support development proposals at planning, but is a FRA always required to support planning and how much will one cost?

To answer this question, we must first understand how the National Planning Policy Framework (NPPF) defines a site-specific FRA, it’s objectives and when the Local Planning Authority (LPA) should consult with the Environment Agency (EA) or the Lead Local Flood Authority (LLFA).

In general, a site-specific FRA will be required when a proposed development site is located within an area of existing flood risk, or the development proposals are classed as major development.

Existing Flood Risk:

This is indicated within government and EA flood maps, which utilise strategic flood modelling to indicate the anticipated flood frequency throughout England and define the Flood Zones for planning. This includes sources of flood risk from rivers or the sea, surface water or from other artificial waterbodies such as reservoirs and canals. Any of these sources of flooding, as well as groundwater, flooding from sewers and historic flood records would be used to inform the need for a FRA.

The LLFA will be a Statutory Consultee on all sites requiring a FRA. The EA would be consulted should the site fall into their Flood Zone or should you propose to discharge your surface water to an EA controlled watercourse.

Major Development:

For housing, NPPF defines major developments as a site where 10 or more homes will be provided, or the site has an area of 0.5 hectares or more. For non-residential development it means additional floorspace of 1,000m2 or more, or a site of 1 hectare or more.

The EA and LLFA will be a Statutory Consultee on Major Developments.

Note that in certain cases the LPA may still consult with the LLFA or EA should the site be classed to be in a critical drainage area.

Based on our experience in dealing with various sites, we have put together the outline Link fees and reasonable 3rd party costs to be considered, as per the tables below.

Outline Budget Allowance

Drainage/Flood Risk StatementFlood Risk Assessment and Drainage Strategy – Major Developments Only
Fewer than 10 dwellings and under 0.5ha site£2,000.00£3,000.00
10-50 Dwellings or small commercial developmentN/A£3,600.00
50-200 Dwellings or larger commercial developmentN/A£4,800.00
200+ Dwelling strategic site, or major commercial developmentN/A£7,200.00+

Note that costs are outline and would depend on site specific constraints, restrictions and existing flood risk.

Developer Enquiries~£350.00
Sewer Records~£50.00
Drainage SurveysVaries
Hydraulic Capacity Assessment*No Cost
Infiltration testing**£1,000.00 - £3,000.00
Watercourse Modelling£12,000+
  • Welsh Water is not subjected to the same statute and will charge for assessments even when in England.

** Infiltration testing to BRE365 will generally be required where infiltration techniques will be utilised for disposing of storm or foul water. We would complete a desktop study review before advising if one is required.

Note that in Wales and Scotland, the basic principles remain, however different bodies and slightly different processes trigger the need for an FRA.

If you’re considering flood risks on your project, we’re here to help. Get in touch with us by emailing

Apr 19, 2022