Material Planning Considerations: Flood Risk

Flood Risk considerations focus on the potential for flooding and the adequacy of measures to prevent and mitigate flood impacts. These considerations ensure that new developments are appropriately located and designed to minimize flood risk to property, people, and the environment.

Key Components of Flood Risk Considerations

Flood Zones and Areas
  • Flood Zone Classification: Areas are classified into different flood zones based on their probability of flooding. This classification helps determine the suitability of different types of development in each zone.
    • Zone 1: Low probability of flooding.
    • Zone 2: Medium probability of flooding.
    • Zone 3a: High probability of flooding.
    • Zone 3b: Functional floodplain, where water is stored during flooding.

Flood Risk Assessments (FRA)
  • Purpose: An FRA evaluates the potential flood risks to and from a proposed development, considering all sources of flooding (rivers, surface water, groundwater, sewers, reservoirs, and coastal).
  • Content: It includes an assessment of existing flood risk, potential impacts of the development on flood risk, and proposed mitigation measures to manage and reduce these risks.

Types of Flooding
  • Fluvial Flooding: Flooding from rivers and streams.

  • Pluvial Flooding: Surface water flooding, often caused by intense rainfall.

  • Groundwater Flooding: Occurs when water levels rise above the surface from underlying aquifers.

  • Tidal Flooding: Flooding from the sea, often exacerbated by high tides and storm surges.

  • Sewer Flooding: Occurs when drainage systems are overwhelmed by heavy rainfall.

Mitigation and Adaptation Measures
  • Flood Defences: Construction of levees, floodwalls, embankments, and barriers to protect against floodwater.
  • Sustainable Drainage Systems (SuDS): Techniques such as permeable pavements, green roofs, swales, and retention basins to manage surface water runoff and reduce flood risk.
  • Building Design: Designing buildings to be flood-resistant and resilient, including raised floor levels, flood barriers, and use of flood-resistant materials.

Sequential and Exception Tests
  • Sequential Test: Ensures that new developments are located in areas with the lowest flood risk by directing development away from high-risk zones.
  • Exception Test: Applied when the Sequential Test indicates that there are no suitable sites in lower-risk zones. It requires that the development provides wider sustainability benefits and that it can be safely managed regarding flood risk.

Impact on Surrounding Areas
  • Flood Storage Capacity: Assess whether the development will reduce the land’s ability to store floodwater, potentially increasing flood risk elsewhere.
  • Runoff and Drainage: Evaluate the impact of increased surface water runoff due to impermeable surfaces and ensure adequate drainage systems are in place.

How Flood Risk Considerations Influence Planning Decisions

1. Flood Risk Assessments:

Planning applications for developments in flood-prone areas must include a detailed FRA. This assessment is crucial for understanding the potential risks and ensuring that appropriate mitigation measures are proposed.


2. Policy Compliance:

Developments must comply with national and local flood risk policies, including those outlined in the National Planning Policy Framework (NPPF) and local development plans.


3. Consultation with Authorities:

Input from the Environment Agency, local flood authorities, and drainage boards is essential. These agencies provide expertise and guidance on managing flood risks and ensuring compliance with regulations.


4. Balancing Development and Flood Risk:

Planning authorities must balance the need for new development with the imperative to manage and reduce flood risk. Developments that pose unacceptable risks or fail to adequately mitigate flood impacts are less likely to be approved.

Importance in Planning Applications

1. Protecting People and Property:

  • Ensuring that developments are not at undue risk of flooding is crucial for protecting the safety and property of residents, businesses, and infrastructure.


2. Sustainable Development:

  • Proper flood risk management is a key aspect of sustainable development, ensuring that new developments do not exacerbate flood risks and are resilient to future climate impacts.


3. Insurance and Financial Implications:

  • Developments in high-risk flood zones can face higher insurance premiums and financial burdens. Ensuring appropriate flood risk management can mitigate these costs.


4. Environmental Protection:

  • Managing flood risk helps protect natural habitats and water quality, preventing erosion, contamination, and loss of biodiversity.


5. Legal and Policy Compliance:

  • Adherence to flood risk policies and regulations is a legal requirement. Non-compliance can result in planning applications being refused or legal challenges.


Conclusion


By thoroughly considering flood risk in planning applications, planning authorities can ensure that new developments are safely located and designed to manage flood risks effectively. This comprehensive approach helps protect people, property, and the environment, promoting sustainable and resilient growth.

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