When Do You Need a Flood Risk Assessment for Planning Permission in England and Wales?

Whether you are planning a barn conversion in Bristol, a new build in Newport or a mixed‑use scheme in Merthyr, understanding when you need a Flood Risk Assessment (FRA) in England or Flood Consequence Assessment (FCA) in Wales is essential for securing planning permission. Flood risk is a core consideration for local planning authorities, and the requirements differ slightly between England and Wales. Getting it right early can save time, avoid costly redesigns and prevent delays further down the line. 

At Ashfield Solutions, we have extensive experience supporting developers, architects, planning consultants and property owners across England and Wales. Our structured, evidence‑led approach helps clients understand risk, satisfy planning policy and build long‑term resilience into their projects.

Planning Triggers in England and Wales

Since the introduction of the revised TAN15 guidance in March 2025, flood risk policy in Wales has become significantly more climate-focused and precautionary. The updated framework places greater emphasis on future flood risk, undefended flood extents and site-specific flood consequence assessments informed by NRW’s Flood Map for Planning. 

Flood Zones/Flood Map for Planning

In England, the Environment Agency’s Flood Zones determine when an FRA is required.

You will need an FRA if your site is in:

• Flood Zone 2 or 3
• Flood Zone 1 but larger than 1 hectare
• Flood Zone 1 with known surface water issues, other local flood risks, or where local evidence/modelled data identifies potential future flood risk from rivers or the sea due to climate change.

Importantly, Flood Zone 1 does not automatically mean flood risk is negligible. Many sites in Flood Zone 1 can still be affected by surface water flooding, groundwater emergence, drainage exceedance or future climate change impacts. Increasingly, local authorities are also considering residual and future flood risk informed by Strategic Flood Risk Assessments (SFRAs) and updated modelling datasets.

In Wales, the planning framework changed significantly following the introduction of the revised TAN15 guidance in March 2025. Natural Resources Wales’ Flood Map for Planning (FMfP) now forms the primary planning flood map, replacing the former Development Advice Map (DAM).

Development proposed within areas identified as being at risk of flooding on the FMfP will typically require a Flood Consequences Assessment (FCA) to demonstrate that the risks and consequences of flooding can be acceptably managed over the lifetime of the development.

Importantly, the Flood Map for Planning differs from the historic DAM mapping as it incorporates updated modelling, climate change impacts over the next century and undefended flood extents. As a result, some sites previously considered acceptable under earlier mapping may now fall within areas requiring further assessment.

Surface Water Risk

Even if a site is in Flood Zone 1, planners may still require an FRA or FCA if mapping shows surface water flood risk. This is a common trigger for urban infill sites, conversions and small extensions.

 

Site Area Thresholds

In England, an FRA is generally required for sites over 1 hectare within Flood Zone 1 due to the potential impacts on surface water runoff and drainage.

In both England and Wales, assessments may also be required where development could significantly alter runoff patterns or where local authorities identify flood-related concerns.

These requirements can apply to developments ranging from single dwellings to large commercial schemes, depending on flood risk and site characteristics. 

What Planners Expect in a Good FRA or FCA

A robust assessment should do more than restate mapping. Planners expect a clear, site‑specific analysis that demonstrates the development is safe, sustainable and policy compliant. A thorough report from Ashfield Solutions typically includes:

• Evidence-based assessment informed by the latest EA, NRW and local authority flood data, mapping and modelling where available. 
• Assessment of all flood sources including fluvial, tidal, surface water, groundwater and artificial sources
• Climate change allowances appropriate to the development type
• Mitigation measures such as finished floor levels, flood resilience and safe access
• Consideration of emergency planning, safe access/egress and flood warning procedures where appropriate to the development type and flood risk

At Ashfield Solutions, we take a clear, step‑by‑step approach that helps clients understand both the risks and the practical measures needed to satisfy planning policy.

Common Mistakes Developers Make

Many planning delays stem from avoidable errors. The most frequent issues include:

Assuming Flood Zone 1 means no risk  

• Surface water flooding is a major cause of planning objections.

Submitting generic or template FRAs  

• Planners expect site‑specific analysis, not generic text.

Ignoring climate change allowances  

• These are mandatory and vary by region and development type.

Overlooking access and egress requirements  

• A development can fail even if the building is safe but the entry route is not.

Not engaging early with the EA/NRW or LLFAs

• Early dialogue can prevent costly redesigns.

Our 20 years of industry experience helps clients avoid these pitfalls and progress applications smoothly.

Real‑World Examples

Two recent projects illustrate how a well‑prepared FRA or FCA can unlock planning permission.

Greater Manchester: New Dwelling in Flood Zone 3

A residential client in Trafford needed an FRA for a new dwelling located between two rivers in Flood Zone 3. Our specialist team compared site levels with Environment Agency flood model data and identified the risk during the 1 in 100 year plus climate change event. We recommended finished floor level adjustments, flood resilient construction and safe evacuation routes. Planning permission was granted on the condition that the development followed Ashfield Solutions’ mitigation strategy.

Pembrokeshire: Brewery Conversion to B&B

In Wales, Ashfield Solutions prepared an FCA for Milton Brewery, which lay within a flood risk area identified by NRW. The assessment demonstrated that the conversion would not increase flood risk to others and that guests could evacuate safely. A site‑specific flood plan and clear evacuation information were incorporated into the approval. NRW raised no objections and planning permission was granted.

These examples show how proportionate, evidence‑based assessments can satisfy regulators even in challenging locations.

Ready to Move Your Project Forward?

If you are unsure whether your project needs an FRA or FCA, or if you want expert guidance on how to secure planning in a flood risk area, Ashfield Solutions can help. Our consultants provide clear, pragmatic advice and a strong approval record with local planning authorities across England and Wales.

On a short time scale? We can often turn around an FRA or FCA in as little as 5 to 10 days, helping clients keep projects on track. 

Contact Ashfield Solutions today on 01443 803 540 to discuss your project and get the clarity you need to move forward with confidence.