The flood risk sequential test has long served as a crucial strategic tool in UK planning, designed to guide new development away from areas at highest risk of flooding by demonstrating that no lower-risk sites are available for the proposed project. Traditionally, this test focused on flooding risks from rivers and seas. However, its application has evolved significantly in recent years, particularly concerning surface water flooding.

Before 2022, surface water flooding—caused when heavy rainfall overwhelms drainage systems—was not typically subject to the sequential test. Instead, surface water flood risk was addressed through drainage strategies within planning applications, recognising the inevitable impact development has on drainage systems via impermeable surfaces or changes to runoff patterns. This distinguished handling made practical sense given the nature of surface water flooding, which usually affected localised areas.

That changed with a 2022 update to the National Planning Practice Guidance (NPPG), which required the sequential test to apply to all flood types, including surface water flooding. This shift meant that even minor and localised surface water flood risks triggered the need for a sequential test in planning applications. The Environment Agency's (EA) surface water flood maps, updated most recently in December 2024, significantly expanded the areas identified as vulnerable to surface water flooding, causing a large increase in sites caught by the sequential test requirement. Local authorities have relied heavily on these EA indications when assessing planning applications.

The simultaneous publication of the updated National Planning Policy Framework (NPPF) in December 2024 maintained this approach, urging a sequential, risk-based assessment for all flood sources—rivers, seas, and surface water alike. While the NPPF introduced a limited exception where no development would occur on flood-prone areas, it largely upheld the need for sequential tests regardless of mitigation measures that could reduce flood risk.

This inflexible policy framework has created practical hurdles for developers, as illustrated by a refusal on a redevelopment project of two dwellings on a former garage site in London due to surface water flood concerns. Despite the small flood-affected area and no increased flood risk from development, the inability to provide a sequential test—given numerous alternative sites within the borough—led to refusal, impeding brownfield redevelopment in accordance with planning policy.

The issue of surface water flooding and sequential test requirements has become a notable barrier to urban development, coinciding with broader concerns about declining planning application rates. In response, the NPPG has been updated in 2025 to adopt a more proportionate stance. The revised guidance now allows for the bypassing of the sequential test if a site-specific flood risk assessment clearly demonstrates that the proposed design and mitigation measures can ensure occupant safety and prevent increased flood risk elsewhere over the development's lifetime. This nuanced approach aligns with the broader government and Environment Agency emphasis on balancing flood risk management with sustainable development.

Government reports and data reinforce the importance of addressing all sources of flood risk in planning. The latest Flood and Coastal Erosion Risk Management Report for 2024-2025 highlights ongoing efforts to enhance flood risk assessments and mapping, including the recognition of surface water flooding risk. The Environment Agency's major update indicates that approximately 6.3 million properties in England face flood risk from rivers, seas, or surface water, emphasizing the need for comprehensive risk management frameworks.

Further government guidance specifies the requirements for flood risk assessments, detailing when the sequential and exception tests apply and advising authorities and developers on procedural and assessment standards. Updates to national flood and coastal erosion risk information incorporate climate change scenarios, improving the accuracy of flood risk mapping and supporting more informed planning decisions.

While the revised NPPG offers a more flexible approach to surface water flood risk and sequential testing, overarching policies continue to advocate for the prioritisation of site locations with the lowest flood risk. The sequential test remains a key mechanism within local plan preparation and planning application reviews to encourage resilient, sustainable development.

In conclusion, the adjustment in 2025 to the application of the sequential test regarding surface water flooding marks a significant step towards a more pragmatic and proportionate regulatory regime. It seeks to strike an appropriate balance between mitigating flood risk and facilitating essential development, particularly on brownfield sites. The changes reflect evolving government priorities and improved understanding of flood risks, helping to reduce avoidable planning obstacles without compromising safety or sustainability.

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Source: Noah Wire Services