BREEAM Flood Risk Assessments Explained

Key takeaways

• A BREEAM flood risk assessment is a site-specific study of a development's flood risk, prepared so it can support BREEAM credits, mainly Pol 03 (Flood and surface water management).
• It uses much the same flood data as a planning FRA but is scored differently: a planning FRA answers to the NPPF and the Environment Agency, a BREEAM FRA to the BREEAM assessor.
• Pol 03 has three parts: flood risk, surface water run-off (benchmarked to The SuDS Manual, CIRIA C753), and minimising watercourse pollution.
• Commission it early, around RIBA Stage 2, so mitigation can be designed in rather than retrofitted, and credits are not lost.
• A well-prepared planning FRA usually provides most of the evidence a BREEAM assessment needs, which avoids paying twice.

What is a BREEAM flood risk assessment?

A BREEAM flood risk assessment is a site-specific study that establishes a development's flood risk and shows how the design responds, prepared so it can support the relevant BREEAM credits. It looks at every source of flooding that could affect the site, rivers and the sea, surface water, groundwater, sewers and artificial sources such as reservoirs or canals, and at how those risks change over the building's lifetime with climate change. It also considers the development's own effect on run-off, and whether it could increase flood risk for neighbours. It is a piece of assessment work, not a desk check against a published map.

Which BREEAM credits flood risk covers

Flood risk and surface-water management sit in BREEAM's pollution category, under the credit Pol 03: Flood and surface water management, in BREEAM UK New Construction 2018 and Version 6. It is worth being precise here, because the credit is often described loosely as just “surface water run-off”. Pol 03 is broader than that, and it has three distinct parts.

Flood-resilient design can also support BREEAM's climate-change adaptation credit (Wst 05 in New Construction 2018), since safe finished floor levels and resilient construction speak directly to a building's long-term resilience. The exact credit references, thresholds and available points depend on the BREEAM scheme and version you are certifying under, so always confirm against the relevant BREEAM scheme manual. One detail worth knowing early: where a site sits in an area protected by existing flood defences, Pol 03 can still award flood-risk credits if the defences reduce the risk to low or medium and certain conditions are met, such as the site being previously developed.

How a BREEAM FRA differs from a planning FRA

A planning FRA is driven by the NPPF and Planning Practice Guidance and has to satisfy the local planning authority and the Environment Agency. If that is what you need, see our guides on how to do a flood risk assessment and why expertise matters in an FRA. A BREEAM assessment is scored against the BREEAM scheme's credit criteria instead. The two are easy to confuse because the underlying work overlaps so heavily.

That overlap is the practical point. The same understanding of the site's flood zone, the same assessment of all flood sources, and the same surface water drainage strategy can serve both purposes when the work is set up with both in mind. A well-prepared planning FRA usually provides most of the evidence a BREEAM assessor needs. Done separately and late, it is where projects pay twice.

When should you commission a BREEAM FRA?

Early. To have the best chance of the Pol 03 credits, the flood-risk work should be done while the layout is still flexible, ideally around RIBA Stage 2 (concept design). That is when flood-mitigation measures such as sustainable drainage, attenuation and sensible finished floor levels can be designed into the scheme rather than retrofitted. Leave it until detailed design or later and you risk losing credits, redesigning drainage, or both. Early assessment is also cheaper, which is the same lesson as the wider question of what an FRA costs.

What a BREEAM flood risk assessment looks at

• The site's flood zone and risk from all sources, taking the worst-case zone where a site spans more than one.
• Proposed finished floor levels and flood-resilience measures, set as they would be for a planning FRA.
• The surface-water drainage strategy and post-development run-off rates and volumes, against the C753 benchmark.
• How climate change shifts the risk across the building's design life.
• Evidence that the design meets the relevant Pol 03 thresholds for the scheme version.

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