Sustainable Drainage Systems (SuDS) Strategy

Here at SWEL we have been writing drainage reports, and landscaping reports for over decade. We also have in house ecologists who can mesh SuDs with BNG to get the very best result for you, in terms of site layout and making the best use of the space you have.

If you have any questions about your SuDS Strategy please email over some plans (big yellow button top of page) and we will get back to you ASAP.

Meeting Modern Planning Requirements

In the current planning landscape, a robust SuDS Strategy is no longer optional. Whether you are working on a minor residential extension or a major commercial development, local authorities require a clear plan to manage surface water at its source. Our expertise ensures your project meets the latest national standards while protecting the local environment from flood risk.

Our Approach: The SuDS Management Train

We don’t just design pipes; we design ecosystems. Our strategies follow the SuDS Management Train, a hierarchical approach that mimics natural drainage:

• Source Control: Managing rainfall exactly where it lands through green roofs, permeable paving, and rainwater harvesting.
• Site Control: Channelling water through swales or detention basins to manage volume and improve water quality.
• Regional Control: Final management of runoff before it enters the wider environment, ensuring no negative impact on downstream receptors.

Why Your Project Needs a SuDS Assessment

A professional SuDS report is critical for:

• Discharging Planning Conditions: Meeting the requirements set by the LLFA and the Environment Agency.
• Biodiversity Net Gain (BNG): Integrating blue-green infrastructure that supports local flora and fauna.
• Water Quality: Providing necessary treatment stages to remove pollutants from surface water before it enters the ground or watercourses.
• Cost Efficiency: Reducing the need for expensive underground storage tanks by utilizing natural, surface-level solutions.

Technical Compliance & Standards

All our SuDS Strategies are developed where feasible to do so in accordance with:

• The SuDS Manual (CIRIA C753): The industry gold standard for design and maintenance
• DEFRA Non-Statutory Technical Standards: Ensuring your drainage system is functional, safe, and sustainable.
• Local Authority Requirements: Tailoring reports to the specific flood risk zones and soil conditions of your site.

Strategic Integration for your Website

Internal Link Suggestion: "For projects requiring comprehensive site-wide water management, explore our Surface Water Management Plans (SWMP) or our Foul and Surface Water Drainage Strategy services."

Frequently Asked Questions: SuDS and Planning

Is a SuDS Strategy mandatory for all planning applications?

In 2026, the National Planning Policy Framework (NPPF) and Schedule 3 of the Flood and Water Management Act effectively make SuDS a requirement for almost all developments. While mandatory for "Major" developments, most Lead Local Flood Authorities (LLFAs) now also require a proportionate SuDS report for "Minor" applications to ensure the development does not increase local flood risk.

What is the "SuDS Hierarchy"?

The SuDS hierarchy is a sequence of preferred discharge methods. Planning officers expect you to prove you have considered them in this specific order:

• Rainwater Reuse: Harvesting for irrigation or non-potable use (on smaller project this can even be treated for potable use)
• Infiltration: Soaking into the ground (subject to soil porosity - BRE 365 Soakaway Test).
• Surface Water Body: Discharging to a river or stream.
• Surface Water Sewer: Piped infrastructure.
• Combined Sewer: Only as a last resort where no other option exists.

What happens if my site has poor infiltration (e.g., heavy clay)?

Poor soil doesn't exempt a site from SuDS. If infiltration isn't viable, the strategy shifts toward attenuation. We design systems like blue roofs, detention basins, or storage tanks that hold the water and release it at a controlled "Greenfield runoff rate" to prevent overwhelming the local network.

Who is responsible for the maintenance of SuDS?

Maintenance responsibility must be clearly defined at the planning stage. Options typically include:

• Adoption by Water Companies: Under the latest standards, many SuDS are now adoptable.
• Management Companies: Common for private residential or commercial estates.
• Local Authorities: For SuDS integrated into public highways or parks. Our reports include a full Maintenance Schedule to satisfy LLFA requirements and ensure the long-term viability of the system.

Can SuDS help with Biodiversity Net Gain (BNG) targets?

Yes. By using "soft" SuDS features like swales, rain gardens, and ponds rather than underground tanks, you can create new habitats. This dual-purpose approach helps developers meet their mandatory 10% Biodiversity Net Gain requirements while managing water. Read our guide on overlapping SuDs with BNG