The Sequential and Exception Tests

The Sequential and Exception Tests are pivotal components of flood risk management in the UK, ensuring developments occur in areas with the lowest possible flood risk. This blog provides a detailed exploration of these tests, their application, and their importance in sustainable urban planning.

The Sequential Test

The Sequential Test aims to direct new developments to areas with the least flood risk, primarily Flood Zone 1. If no suitable sites are available in Zone 1, developers must justify using land in Zone 2 or Zone 3. This process ensures that:

1. Development is located to minimize risk to life and property.

2. Pressure on high-risk areas, such as functional floodplains, is reduced.

Key tools, such as local Strategic Flood Risk Assessments (SFRAs) and national flood maps, are used to evaluate site suitability. Additionally, urban expansion plans often integrate Sequential Test findings to align growth with flood resilience.

The Exception Test

When development in high-risk areas (Zones 2 or 3) is unavoidable, the Exception Test ensures the proposal is justified and sustainable. For a development to pass this test, it must:

1. Demonstrate substantial sustainability benefits that outweigh the flood risk, such as providing essential infrastructure or addressing housing shortages.

2. Ensure the development will be safe for its entire lifespan without increasing flood risks elsewhere. This involves detailed assessments of flood defenses, access routes during floods, and building resilience.

For example, residential developments must address a lifespan of at least 100 years, incorporating climate change impacts into their risk assessments. Commercial properties typically plan for a 75-year horizon.

Practical Application

In practice, these tests are embedded in the planning process to make informed, data-driven decisions. Case studies from councils such as those in London and Somerset highlight how Sequential and Exception Tests shape sustainable development. For example:

• Sequential Test in Urban Expansion: Areas like Milton Keynes have used Sequential Tests to prioritize housing developments in low-risk zones, avoiding known floodplains.

• Exception Test Example: Infrastructure projects, such as hospitals in Zone 3, justify their placement through critical need and mitigation measures like elevated foundations and improved drainage systems.

Strategic Flood Risk Assessments (SFRAs) and partnerships with the Environment Agency provide essential data, including climate change projections, for robust decision-making. Developers must consult multiple datasets and scenario models to align projects with long-term safety and sustainability goals.

For more detailed guidance, consult the UK Government’s page on Sequential and Exception Tests - GOV.UK.