Sequential and Exception Tests Explained: Navigating the Updated NPPF and National Flood Risk Standing Advice

Flood risk management in the UK continues to evolve as new policies and guidance reshape how developments are assessed and approved. The revised National Planning Policy Framework (NPPF) and updates to the National Flood Risk Standing Advice for local authorities have introduced significant changes to the Sequential Test process, influencing how planners and developers approach flood risk mitigation.

What is the Sequential Test?

The Sequential Test is a planning tool designed to steer new developments to areas with the lowest probability of flooding. By directing development to lower-risk areas (Flood Zone 1 first, then Zone 2, and so on), the test minimizes flood risk to people and property. If development in higher-risk zones (Flood Zones 2 or 3) is unavoidable, developers must provide robust evidence to justify their choice.

Recent Changes to the NPPF: Paragraph 175

The 2021 revisions to the NPPF, particularly Paragraph 175, introduce a nuanced approach to the Sequential Test:

• Site-Specific Assessment Priority: Developments no longer automatically require a Sequential Test if a site-specific flood risk assessment (FRA) demonstrates that vulnerable elements (e.g., buildings, access, or escape routes) are excluded from areas at risk of flooding.

• Exclusion Zones Within Sites: Developers are encouraged to use natural flood-prone areas within a site for non-vulnerable purposes, such as public open spaces, biodiversity enhancements, or sustainable drainage systems (SuDS). These uses align with flood mitigation goals while allowing developments to proceed without fully relocating.

• Forward-Looking Flood Risk Assessments: The Sequential Test and site layouts must account for current and future flood risks, including potential changes caused by climate change.

This flexibility reflects the government’s aim to balance development needs with sustainable flood risk management.

Key Implications for Local Authorities and Developers

The updates to the NPPF and Standing Advice shift how local authorities evaluate Sequential Tests:

1. Increased Reliance on Site-Specific FRAs: Local authorities can waive the Sequential Test if an FRA confirms that all vulnerable components are sited in flood-free areas within the proposed site. Developers must work closely with flood risk consultants to ensure robust and compliant FRAs.

2. Creative Land Use Planning: Developers are incentivized to integrate flood-prone areas into site layouts as multifunctional spaces, such as:

   • Parks and recreational facilities

   • Wildlife habitats or wetlands

   • SuDS features like swales or retention ponds

   This not only mitigates flood risks but also enhances the site’s overall amenity and biodiversity value.

3. Broader Application of Sequential Test Principles: Paragraph 175 of the NPPF clarifies that the Sequential Test applies to all forms of flooding (not just river and sea flooding). This includes surface water flooding, groundwater flooding, and reservoir breach scenarios. Developers must evaluate risks from all potential sources.

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National Flood Risk Standing Advice: Simplifying the Sequential Test

The National Flood Risk Standing Advice for local authorities complements the NPPF, providing practical guidance for implementing the Sequential Test. Key highlights include:

• Reduced Test Scope for Certain Developments: Developments that strategically locate flood-sensitive features away from high-risk areas may not need a full Sequential Test. For example, a housing development where flood-prone areas are used exclusively for open space can bypass certain Sequential Test requirements.

• Defining "Reasonably Available" Sites: The advice emphasizes defining the geographical search area and scope for alternative sites, ensuring a focused and proportional approach to the Sequential Test.

• Prioritizing Climate-Resilient Design: Standing Advice reinforces the importance of addressing climate impacts, including higher rainfall intensities and sea-level rise, when identifying flood-safe development layouts.

  
  

Case Study: Integrating Flood Risk with Urban Development

A proposed residential development in Flood Zone 3a highlights how Paragraph 175 can shape planning outcomes:

• Site-Specific Layout: Housing and access roads are located in Flood Zone 1 areas within the site, while flood-prone zones are reserved for public green space and a wildlife corridor.

• Biodiversity Benefits: The flood-prone areas were planted with native wetland vegetation, creating habitats for local wildlife.

• Community Resilience: SuDS features like swales and retention basins were incorporated to manage surface water runoff.

This approach allowed the development to proceed without requiring a Sequential Test, aligning with Paragraph 175’s flexibility.

Conclusion: Balancing Development and Flood Resilience

The updated NPPF and National Flood Risk Standing Advice provide a more flexible framework for managing flood risk in development planning. By integrating site-specific assessments, innovative land use, and climate resilience, developers and planners can navigate flood risks while supporting sustainable growth. These changes not only streamline the Sequential Test process but also encourage creative, multi-benefit solutions to modern flood challenges.