Exploring the SuDS Hierarchy: A Sustainable Drainage Strategy for Modern Development

Sustainable Drainage Systems (SuDS) are at the forefront of modern water management strategies, designed to mitigate flooding, enhance water quality, and provide environmental and community benefits. Central to effective SuDS design is the SuDS hierarchy, a structured approach that prioritizes techniques for managing surface water at its source, promoting infiltration, and minimizing reliance on conventional drainage systems.

Understanding the SuDS Hierarchy

The SuDS hierarchy is a set of guiding principles that determine the preferred order of methods to manage surface water. It reflects a shift from traditional engineered solutions toward more sustainable and integrated systems. The hierarchy is structured to prioritize nature-based solutions, which align with environmental and hydrological processes.

1. Prevention: Reducing Runoff at the Source

Goal: Minimize surface water generation.

• Approach:

  • Incorporate permeable surfaces, green roofs, and soft landscaping.

  • Design buildings and infrastructure to integrate water conservation practices.

• Example: A residential area designed with permeable driveways reduces the volume of surface runoff by allowing water to infiltrate into the ground.

2. Source Control: Managing Water Where It Falls

Goal: Retain or use water as close to its source as possible.

• Techniques:

  • Rainwater Harvesting: Collect rainwater for reuse in irrigation or non-potable domestic uses.

  • Green Roofs: Vegetated roof systems that absorb and slow down rainwater.

  • Soakaways: Underground structures that store water and allow gradual infiltration into the soil​.

3. Site Control: Managing Water Across Development Sites

Goal: Handle surface water collectively from multiple properties or infrastructure areas.

• Techniques:

  • Swales: Shallow vegetated channels that convey water while promoting infiltration and pollutant removal.

  • Bioretention Systems: Landscaped areas designed to capture and treat runoff, such as rain gardens.

• Benefits: Enhance biodiversity and create aesthetically pleasing green spaces​CIRIA report.

4. Regional Control: Larger-Scale Solutions

Goal: Provide a cohesive drainage strategy for larger developments or urban regions.

• Examples:

  • Retention Basins: Large basins designed to hold stormwater temporarily and release it slowly.

  • Wetlands and Ponds: Create habitats while managing and treating surface water.

  • Attenuation Tanks: Underground tanks to store water, often used in conjunction with other SuDS components​.

    
    

Key Benefits of Following the SuDS Hierarchy

1. Flood Risk Management: Reduce the likelihood and severity of urban flooding.

2. Water Quality Improvement: Filter pollutants naturally through vegetation and soils.

3. Biodiversity Enhancement: Support ecosystems with habitats such as wetlands and ponds.

4. Community Amenity: Provide recreational spaces and improve urban aesthetics​CIRIA report C753 The S…​A-Place-for-SuDS.

   
   

Challenges and Opportunities

While SuDS offer numerous benefits, they face challenges, including:

• Urban Constraints: Limited space for larger features in dense developments.

• Maintenance Requirements: Ensuring ongoing functionality and aesthetics.

• Policy and Planning Gaps: Variability in local regulations and guidance.

However, with thoughtful integration and early planning, these systems can transform urban landscapes, providing resilience to climate change and creating vibrant, sustainable communities.

Development and Planning Implications

The National Planning Policy Framework (NPPF) and associated Planning Practice Guidance (PPG) reference Sustainable Drainage Systems (SuDS) as an essential component of managing surface water in new developments. Below are the key points of reference:

1. NPPF References:

   • Paragraphs 167 and 169 emphasize that major developments should incorporate SuDS unless demonstrated to be inappropriate. It also highlights the need to consult relevant flood risk management bodies like the Lead Local Flood Authority (LLFA)​Flood risk and coastal ….

   • The NPPF integrates SuDS within the broader scope of reducing flood risks and ensuring sustainable water management for developments, aligning with climate change mitigation goals​.

2. Planning Practice Guidance (PPG):

   • The PPG supports the NPPF by outlining the necessity for local planning authorities to ensure that development proposals adhere to minimum operational standards for SuDS. It also addresses long-term maintenance and economic proportionality of the systems​Flood risk and coastal.

   • It specifies that SuDS should mimic natural drainage paths and minimize the impact on off-site flood risks, ensuring that both permeable and impermeable surfaces are considered​

3. Implementation Requirements:

   • Developers of major projects must include a drainage strategy within their planning applications to demonstrate compliance with SuDS standards. This often involves a site-specific flood risk assessment​Flood risk and coastal ….

4. Consultation and Maintenance:

   • The PPG mandates consultation with LLFAs to assess the feasibility and practicality of SuDS systems. Local planning authorities are also responsible for ensuring appropriate maintenance mechanisms are in place for the lifetime of the development​.

Conclusion

The SuDS hierarchy emphasizes a progressive, sustainable approach to surface water management, promoting ecological harmony and resilience. By adhering to these principles, developers, planners, and policymakers can address flood risks, improve water quality, and enhance the urban environment in a way that benefits both people and nature.

For a deeper dive into technical specifics and case studies, consult resources such as CIRIA's SuDS Manual and CIWEM's sustainable drainage guidelines​.