How to Apply and Navigate the Sequential Test for a Development Site

Flood risk is a pressing concern in urban planning, with both national and local policies prioritizing the safety of people and property. One of the key tools for achieving this is the Sequential Test, a process designed to steer new developments away from areas at higher flood risk. This comprehensive guide explains how to apply the Sequential Test to a site, ensuring compliance with regulatory standards and promoting sustainable development.

What is the Sequential Test?

The Sequential Test is a fundamental aspect of flood risk management, embedded in the National Planning Policy Framework (NPPF). Its aim is simple yet critical: to direct development to areas with the lowest probability of flooding. This involves assessing whether there are alternative sites available that are less susceptible to flooding before proceeding with a proposal in a higher-risk flood zone.

The test applies to developments located in Flood Zones 2 and 3 (medium to high flood risk), unless exempt due to specific circumstances, such as minor extensions or changes of use.

Understanding Flood Zones

Flood zones, as defined by the Environment Agency, categorize areas by their flood risk:

• Zone 1: Low probability (less than 1 in 1,000 annual probability of flooding).

• Zone 2: Medium probability (1 in 100 to 1 in 1,000 for river flooding; 1 in 200 to 1 in 1,000 for sea flooding).

• Zone 3a: High probability (1 in 100 or greater for river flooding; 1 in 200 or greater for sea flooding).

• Zone 3b: Functional floodplain, where water is stored during floods

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The Sequential Test Process

Applying the Sequential Test involves several stages, outlined below:

1. Defining the Search Area

The first step is to identify the geographical area for alternative site assessment. This can range from a specific locality to the entire local planning authority (LPA) area, depending on the type and scale of the development. For example, a local housing project may limit the search to nearby urban centers, while a regional logistics hub might necessitate a broader search.

2. Identifying Alternative Sites

Compile a list of alternative sites within the defined area. Potential sources include:

• Strategic Housing Land Availability Assessments (SHLAA).

• Local Plan allocations.

• Estate agent listings or auction data for windfall sites.

  
  

3. Assessing Reasonable Availability

Evaluate the suitability of alternative sites using these criteria:

• Flood Risk: Preference is given to sites in lower-risk zones.

• Development Compatibility: Assess whether the site meets the project’s functional needs.

• Availability: Determine if the site is available for purchase or development within the required timeframe.

• Deliverability: Ensure the site can support the proposed development without significant constraints

  
  

4. Comparing Sites

Once alternative sites are identified, compare their flood risk profiles using data from sources such as:

• Environment Agency Flood Maps.

• Local Strategic Flood Risk Assessments (SFRAs).

• Site-specific Flood Risk Assessments (FRAs)

If no suitable alternative exists, the Sequential Test is considered passed.

Documenting the Test

When submitting a Sequential Test, include the following:

1. Written Justification: Explain the chosen search area and methods for identifying alternative sites.

2. Flood Zone Maps: Include maps to illustrate flood risks across assessed sites.

3. Assessment Summary: Provide a comparative analysis of all identified sites.

The final document should clearly demonstrate that the proposed site is the most appropriate option in the context of flood risk and development objectives

The Exception Test

In some cases, even if a site is in a higher flood risk zone, the development may proceed if it passes the Exception Test. This applies when:

1. The development provides wider sustainability benefits that outweigh the flood risk.

2. A detailed site-specific FRA demonstrates that the development will be safe for its lifetime and will not increase flood risk elsewhere.

For example, regeneration projects in urban centers might pass the Exception Test if they address critical housing shortages or economic growth.

Case Study: Applying the Sequential Test in Practice

Imagine a developer proposes a residential project on a site in Flood Zone 3a. Here’s how the Sequential Test might unfold:

1. Defining the Area: The LPA defines the search area as the local town and neighboring suburbs.

2. Alternative Sites: The developer identifies several sites from the SHLAA and estate listings.

3. Flood Risk Analysis: Most alternative sites are in Zone 1 or 2, but they lack the required infrastructure or exceed budget constraints.

4. Justification: The developer submits evidence that no other site is reasonably available, passing the Sequential Test.

   
   

Tips for a Successful Sequential Test

1. Engage Early: Consult the LPA and Environment Agency during the planning phase to clarify expectations.

2. Focus the Search: Narrow the search area to relevant locations to save time and resources.

3. Document Thoroughly: Provide robust evidence for site assessments and decisions.

4. Address Sustainability: Highlight how the development aligns with broader community and environmental goals.

   
   

Beyond Compliance: The Role of Sustainable Drainage Systems (SuDS)

Incorporating SuDS can mitigate flood risks by managing surface water sustainably. Examples include:

• Green roofs and permeable pavements to reduce runoff.

• Swales and infiltration basins for water capture.

• Rainwater harvesting for reuse.

By integrating SuDS, developers enhance site safety and align with best practices in urban design.

Conclusion

The Sequential Test is more than a regulatory hurdle; it’s a vital mechanism for safeguarding communities and fostering resilient development. By systematically applying the test, documenting findings, and embracing innovative drainage solutions, developers can contribute to sustainable growth while minimizing flood risk.

Whether you’re a planner, developer, or stakeholder, understanding and executing the Sequential Test ensures projects align with environmental and societal needs, building a safer future for all.