How Much Does a Flood Risk Assessment Cost in 2026?

One of the first questions developers and planning consultants ask when they discover an FRA is required is: how much will it cost? The honest answer is that it depends — but that does not mean it is unpredictable. Understanding what drives FRA costs will help you budget accurately and avoid surprises.

This guide sets out typical price ranges for different types of flood risk assessment in 2026, explains the factors that affect cost, and offers practical advice on managing your FRA budget.

Typical Price Ranges

The cost of a flood risk assessment in the UK varies significantly depending on the type of assessment required, the complexity of the site, and whether hydraulic modelling is needed. The following ranges reflect typical market rates in 2026.

Desktop FRA: £750 - £3,000

A desktop flood risk assessment is a desk-based review using publicly available flood mapping, historical records, and published flood levels. No original modelling or fieldwork is involved. This is appropriate for:

• Small sites in Flood Zone 2 where published EA flood levels are available.
• Sites in Flood Zone 1 that exceed 1 hectare and need to address surface water and drainage.
• Change-of-use applications where the vulnerability classification is increasing.

The lower end of the range (£750 - £1,200) covers straightforward single-plot or minor development assessments. More complex desktop FRAs for larger or multi-constraint sites will be towards the upper end (£1,500 - £3,000).

Detailed FRA with Modelling: £5,000 - £15,000+

A detailed FRA involves commissioning original hydraulic modelling to quantify flood risk with site-specific precision. This is required where existing EA modelling is unavailable, outdated, or insufficient for the scale of the proposed development.

Cost drivers within this range include:

• 1D fluvial modelling only: £5,000 - £8,000. Suitable for straightforward river sites where a 1D model is sufficient.
• 2D surface water modelling: £5,000 - £10,000. Direct rainfall modelling using TUFLOW or similar to assess pluvial flood risk.
• 1D-2D linked modelling: £8,000 - £15,000. Combined channel and floodplain modelling for complex fluvial sites.
• Breach modelling: Add £2,000 - £5,000. Required for sites behind flood defences to assess residual risk.

Very large or complex sites — NSIPs, multi-phase developments, or sites with multiple flood sources — can exceed £15,000 and occasionally reach £25,000 or more.

Drainage Strategy / SuDS Design: £2,000 - £8,000

While not strictly part of the FRA, a drainage strategy or SuDS design is almost always required alongside the flood risk assessment. Many consultants, including Aegaea, offer combined FRA and drainage packages that represent better value than commissioning these separately.

A basic drainage strategy for a small residential site might cost £2,000 - £3,500. A detailed SuDS design for a major housing development with attenuation calculations, treatment stages, and adoption-ready details will be £5,000 - £8,000 or more.

What Affects the Cost?

Several factors influence the cost of an FRA. Understanding these will help you anticipate whether your project is likely to fall at the lower or upper end of the price ranges above.

Flood Zone and Flood Sources

Sites in Flood Zone 1 with only surface water risk are generally cheaper to assess than sites in Flood Zone 2 or 3 where fluvial or tidal modelling may be needed. Sites affected by multiple flood sources — for example, a site at the confluence of two rivers with additional tidal and surface water risk — will cost more because the assessment needs to address each source.

Site Size and Complexity

Larger sites require more extensive analysis. A 0.1-hectare plot for a single dwelling is fundamentally different from a 50-hectare strategic allocation. Larger sites also tend to involve more complex drainage calculations, more stakeholder consultation, and more detailed reporting.

Site topography matters too. A flat, unconstrained greenfield site is cheaper to assess than a steeply sloping urban site with multiple buildings, culverted watercourses, and constrained drainage outfalls.

Availability of Existing Data

If the Environment Agency has existing detailed modelling that covers your site, flood levels can often be extracted from the existing model without commissioning new modelling. An EA data request typically costs £100 - £300 (payable to the EA) and provides model results that can be used in the FRA.

If no existing modelling is available, or if the existing modelling is outdated, new modelling will be required — and this is the single biggest cost driver.

EA Pre-Application Advice

The Environment Agency offers a pre-application advice service that allows you to discuss the FRA scope, modelling approach, and key technical issues before commissioning the work. This service is free for most planning applications and is highly recommended for any site where modelling may be required.

A pre-application discussion can save significant money by confirming the EA’s expectations upfront. It avoids the risk of commissioning modelling that the EA considers inadequate (requiring rework) or modelling that the EA considers unnecessary (wasted expenditure).

LLFA and Water Company Consultation

In addition to the EA, you may need to consult the lead local flood authority (LLFA) regarding surface water management and the water company regarding sewer capacity and discharge rates. Some LLFAs charge for pre-application advice; others provide it free of charge. Water company sewer capacity assessments may also attract a fee.

Tips to Manage FRA Costs

1. Commission Early

The single most effective way to manage FRA costs is to commission the work as early as possible. Rushed FRAs cost more because they require premium service, and they are more likely to contain gaps that trigger EA objections and subsequent rework.

If you know an FRA is likely to be required, instruct it at the pre-application stage. This allows adequate time for data acquisition, modelling (if needed), and EA engagement without programme pressure.

2. Combine FRA and Drainage

Commissioning the flood risk assessment and drainage strategy from the same consultant is almost always cheaper than splitting them between two firms. The consultant gains efficiency by using the same site data, flood risk understanding, and stakeholder relationships for both workstreams. At Aegaea, we offer combined packages that deliver meaningful savings compared to separate commissions.

3. Use EA Pre-Application Advice

As noted above, a pre-application discussion with the EA is free and can prevent wasted expenditure. Confirm the EA’s expectations before you brief your consultant, and share the EA’s response with the consultant so they can scope the work accurately.

4. Request a Fixed Fee

Most flood risk consultants, including Aegaea, offer fixed-fee quotations for FRA work. A fixed fee gives you cost certainty and avoids the risk of scope creep inflating the bill. Ensure the quotation clearly defines the scope, the deliverables, and any assumptions or exclusions.

5. Check Whether a Screening Assessment Is Sufficient

Not every site needs a full FRA. Some sites in Flood Zone 1 below 1 hectare may only need a brief flood risk statement or screening note rather than a formal FRA. Ask your consultant whether a lighter-touch assessment would satisfy the LPA’s requirements — it could save you several hundred pounds.

Getting a Quote

If you have a site that needs a flood risk assessment, we are happy to provide a fixed-fee quotation based on a brief review of the site location, flood zone, and proposed development. You can request a quote by providing the site address or postcode, the proposed development type, and the planning authority.

We typically respond with a quotation within 24 hours and can start work immediately upon instruction. For sites where modelling is likely to be required, we will advise on the expected programme and any data acquisition that needs to happen before the modelling can begin.