The UK is increasingly exposed to droughts and floods, sometimes within weeks of each another. To stem the tide and improve flow, local planning teams must engage with experts using integrated approaches to mitigation.
The challenge the UK faces is essentially twofold. First, the hydrological volatility we are now seeing makes simple, single-solution approaches risky. Second, available urban land is limited. Nature-based SuDS such as swales, rain gardens and attenuation ponds deliver on the four pillars of SuDS by helping biodiversity, providing amenity, and managing water quantity, and quality.
But sustainable drainage solutions (SuDS) often require significant space to be effective. Manufactured systems include channels, permeable paving, attenuation tanks and blue roofs. These tend to be more compact and are often essential where space is constrained. Often, nature based solutions function at their best when part of a system that also uses engineered solutions. We should exploit the synergies and see the distinction is (arguably) somewhat arbitrary.
The focus of any good SuDS scheme should be safe and effective water management that keeps people and water safe. A practical framework for project teams to achieve this is planning SuDS around a clear set of functional goals: collect, clean, hold and reuse. Each goal can be met more reliably when nature-based and manufactured measures are integrated.
Design for changing rainfall patterns
Collecting surface water begins with correct hydraulic specification. Rainfall patterns are shifting and return-period assumptions must be revisited. Design teams should model for extremes, for example, creating a SuDS that can handle a 1-in-100-year storm and 40% uplift in climate change.
Most urban sites cannot accommodate extensive swales, so strategically placed channels can intercept runoff and direct the flows towards treatment or attenuation zones. These integrated designs ensure that collection systems are not under-specified and that high-risk runoff is safely conveyed.
Combine passive treatment and proprietary filtration
Cleaning stormwater is essential to protect the downstream environment from suspended solids, hydrocarbons and heavy metals. Nature-based elements such as swales and ponds offer effective, low-maintenance pollutant mitigation in low-pollution catchments, and deliver benefits for biodiversity and amenity. However, industrial yards, busy highways and carparks — areas that see higher pollution – could easily produce more pollution than a system using only nature based solutions could handle. In this case, engineered intervention.
Proprietary systems that use sedimentation, vortex separation or targeted filtration can be integrated into the SuDS chain to ensure site-specific water-quality targets are met. In practice, designers should assess pollution risk based on the Simple Index Approach across the site and deploy a combination of passive nature based solutions and engineered filters to achieve compliance with guidance from construction non-profit CIRIA and local planning expectations.
Optimise space with geocellular and rooftop attenuation
Holding and attenuating water upstream avoids overloading drains and watercourses. Where land is available, ponds and wetlands may be suitable solutions, though tanks can be installed where land is limited.
In dense urban developments, however, burying large tanks may be impractical. Geocellular attenuation systems that sit above rooftops provide workable alternatives that conserve ground space while delivering equivalent storage capacity.
By modelling tank volumes and discharge characteristics with appropriate hydraulic software, design engineers can size systems precisely and tune outflow rates to protect downstream networks. Effective schemes use geocellular structures and blue-green roof solutions alongside surface-level nature based solutions to distribute storage across the site, reducing single-point failure risk.
Create circular water flows where feasible
Opportunities to reuse collected water should be evaluated early in the design process. Stored surface and roof runoff can sustainably supply irrigation for green roofs and landscaping, or be used for non-potable applications where regulations and site constraints permit.
Integrating reuse reduces mains demand which has a significant benefit in water-stressed regions and strengthens the case for SuDS during planning negotiations. When reuse is implemented, maintenance and water-quality pathways must be carefully specified to avoid unintended ecological impacts.
Options for optimisation
A core advantage of approaches that use a comprehensive SuDS strategy is spatial optimisation. Manufactured solutions can be designed to channel and pre-treat high-volume or high-pollution runoff, enabling smaller, more resilient nature-based features to provide ecological and amenity benefits without being overwhelmed. For instance, channels within a carpark can direct runoff into a constructed pond, while sediment traps or vortex separators protect planted swales from excess silt. This sequencing preserves the function and longevity of nature based solutions and reduces lifecycle maintenance burdens.
Regulatory pressure and procurement realities
Regulation is tightening and sustainable drainage is already a statutory requirement in parts of the UK, and is expected to feature more widely in future planning decisions. Tender teams must therefore build SuDS strategies that are demonstrably robust, maintainable and costed over whole-life horizons. Engagement with sustainable drainage specialists in the earliest project phases avoids costly retrofits and helps align objectives with sustainability and biodiversity while ensuring sites meet user needs.
Expertise matters
Designing and delivering effective SuDS is a specialised task that benefits from multidisciplinary collaboration. Planners, landscape architects, civil engineers and other key stakeholders should be involved from scheme inception to ensure site constraints, budget and future maintenance regimes are properly balanced. Early collaboration helps to avoid under-specification, secure planning consent and deliver long-term performance.
Where developers combine engineered collection, robust treatment trains, geocellular storage and targeted NbSs, they create systems that are both effective and site-enhancing.
As pressures on the UK’s water resources intensify, the most effective approach is neither purely nature-based nor purely manufactured. It is a strategically engineered system that considers each treatment approach based on its long-term feasibility and cares for water while respecting spatial and economic realities. For project teams preparing the next generation of developments, it is important to consider all viable options as allies that support one another to provide effective and sustainable drainage now, while accounting for increased frequency and intensity or storms, floods and droughts in the future.
David Smoker is Technical Director for water management specialist ACO Technologies.
Image: ACO Technologies
More Features & Opinion:
When the media misreported a human population study, and everyone panicked
A landscape approach to tackling deforestation gives businesses competitive edge
AI and smart innovation can help tackle the food waste crisis
