While policy and standards continue to evolve, the successful delivery of Sustainable Drainage Systems (SuDS) ultimately depends on how they are interpreted, specified, implemented and maintained in practice.

The updated National Planning Policy Framework (NPPF) has reinforced the importance of SuDS within the planning process, requiring all major developments to incorporate Sustainable Drainage Systems unless there is clear evidence that their use would be inappropriate. For Tier 1 contractors and designers, this planning-led approach places greater emphasis on practical, buildable solutions that align with both policy expectations and site realities.

From regulation to responsibility

The original intention behind Schedule 3 of the Flood and Water Management Act was to formalise the approval and adoption of drainage systems, placing clear responsibilities on developers and authorities.

While Schedule 3 remains unimplemented in England, the updated NPPF has strengthened the role of planning policy in driving SuDS adoption. Major developments, typically defined as schemes of 10 or more homes or sites of 0.5 hectares or greater, are now expected to incorporate SuDS that comply with the latest National Standards for Sustainable Drainage Systems unless there is compelling evidence that this would be inappropriate.

As part of the planning process, Local Planning Authorities and Lead Local Flood Authorities increasingly require applicants to demonstrate how systems will be maintained throughout the lifetime of the development, ensuring long-term performance and resilience.

In the absence of a dedicated approval body, responsibilities have not disappeared; they have simply become more distributed. Planning authorities, consultants, contractors and developers must now work more collaboratively to ensure that drainage strategies meet the expectations set out in national policy, technical standards and local requirements.

Integrating flood mitigation into design

Flood mitigation is no longer a standalone consideration. It must be embedded into the overall design of a development, influencing layout, levels, infrastructure and material selection.

Effective systems must address the full water management cycle, including the capture, control, conveyance, storage, treatment and discharge of surface water. This holistic approach ensures that runoff is managed efficiently, reducing the risk of flooding both on and off site.

Designers must therefore consider how different components interact, ensuring that no single element is overloaded or isolated from the wider system.

Making SuDS deliverable on site

One of the key challenges in the current landscape is ensuring that SuDS designs are not only technically sound, but also practical to construct.

Complex systems with multiple components and interfaces can introduce risk during installation, particularly under tight programme constraints. This has driven increased interest in solutions that simplify construction without compromising performance.

Precast and modular systems, for example, can help to standardise installation, reduce variability and improve programme certainty. Similarly, integrated solutions such as combined kerb drainage or linear channel systems can reduce the need for extensive pipe networks, simplifying both design and construction.

These approaches support a more efficient delivery process, helping contractors to meet both technical and commercial objectives.

Selecting the right solution for the site

No single drainage solution is suitable for every project. Designers must carefully consider the characteristics of each site, including space availability, ground conditions, hydraulic requirements and long-term maintenance needs.

In some cases, above-ground SuDS features may be appropriate, providing visible water management and additional environmental benefits. In others, particularly in dense urban environments or infrastructure-led schemes, hidden or below-ground solutions may be required.

Slot drainage systems, for example, offer a discreet method of surface water interception, integrating with paving and hard landscaping to minimise visual impact. Combined kerb drainage, meanwhile, allows for efficient capture and conveyance of runoff along road edges, supporting both performance and constructability.

The key is not the choice of any single system, but how effectively different elements are combined to create a coherent and resilient drainage strategy.

Bridging the gap between design and delivery

As expectations around SuDS continue to evolve, the alignment between design and construction becomes increasingly important.

Designers must account for how systems will be installed, maintained and operated over time, while contractors must understand the intent behind specifications to ensure accurate delivery. Early collaboration across the project team can help to identify potential challenges, reduce risk and improve overall outcomes.

This is becoming increasingly important as planning submissions are expected to demonstrate not only hydraulic performance, but also compliance with NPPF requirements, adherence to National SuDS Standards and a clear strategy for ongoing maintenance. Deliverability and long-term operation are now key considerations from the earliest design stages.

This is particularly important in a planning-led environment, where approval is based not only on technical calculations, but on demonstrating that a scheme will function effectively in practice.

Conclusion

The continued delay in implementing Schedule 3 has shifted the emphasis towards a planning-led approach to SuDS delivery. With the NPPF now requiring SuDS on major developments as the default position, designers and contractors have a critical role in translating policy requirements into practical, effective solutions.

By focusing on integrated, maintainable and buildable drainage strategies, the industry can deliver systems that satisfy planning requirements, support long-term flood resilience and prepare projects for future regulatory change.

Ultimately, successful SuDS delivery depends on more than policy; it relies on the ability to translate design intent into real-world performance, creating developments that are both resilient and sustainable.

These additions create a stronger link between the article's practical focus and the current regulatory landscape, while naturally introducing the NPPF, major development threshold, National Standards and maintenance-plan requirements.

Written By

Benjamin Birkhead

Benjamin Birkhead is part of the Marshalls Design Team, providing value-engineered permeable paving solutions to customers. 

Read Ben's full profile here.