Decision-makers must square two connected problems: intense storm runoff and increasing scarcity of drinkable and potable H20. On-site water management emphasising deliverability and ecological protection can help.
Across the UK, water infrastructure faces multiple pressures. Reduced availability threatens household supplies and, where irrigation is necessary, jeopardises agricultural production and food security. At the same time, pollution, nutrient-management issues and repeated discharges of raw sewage are degrading rivers, coasts and habitats. Recent storms have shown how drainage systems can be overwhelmed and how floodwater is a hazard that we cannot afford to ignore. The challenge is not to choose between scarcity and flooding, but to design systems that addresses both.
Progress requires carefully considered design, wider adoption of Sustainable Drainage Systems (SuDS), and use of both nature-based and engineered measures. A simple methodology to follow is ‘collect, clean, hold, reuse’. By keeping these principles in mind at each stage of a project, we can start to reverse the problems we’ve been seeing.
Capturing runoff at source
Begin by planning how water will be intercepted and routed. Drainage channels on site should have sufficient hydraulic capacity to handle expected rainfall. At sustainable water management specialist ACO, modelling is based on a 1-in-100 event with a 40% increase to account for climate change. These assumptions help avoid under-specifying channels and downstream impacts.
Protecting quality before discharge
Collected runoff should be treated before it leaves the site. Treatment targets include suspended solids, hydrocarbons (oils), heavy metals, debris and litter. During early design, teams can use the Simple Index Approach to determine which SuDS components are appropriate for a given surface water runoff regime. Options include nature-based solutions (NbSs) such as swales and ponds, as well as proprietary systems where site constraints or performance requirements demand engineered alternatives.
Managing volumes through retention
To prevent watercourses and sewers from being overwhelmed, water should be held on site and released slowly. Plans should incorporate NbSs where possible since they can support biodiversity and local amenity while also providing attenuation. Where NbSs are impractical due to space or logistics, manufactured attenuation systems can retain volumes and release them slowly. Specialist modelling tools are valuable at this stage to size attenuation tanks accurately and to simulate outflow performance.
Designing for beneficial reuse
Planning for reuse should be part of any scheme from the very beginning and NbSs such as swales and attenuation ponds can provide local ecological value while serving as reservoirs for reuse. New drainage technologies increasingly mimic NbSs, which is often a benefit in cases where space is at a premium. Blue and blue-green roofs, for example, hold water in rooftop tanks that feed plants on green roofs, offering an alternative in scenarios where burying attenuation tanks is not a viable option.
Bridging innovation and delivery
Those involved in planning will recognise the need to bring standards, modelling and site-specific decisions together. Referencing the CIRIA SuDS Manual and the National SuDS Standards will mean robust assumptions can be embedded as part of the modelling stage and give teams a strong technical baseline to work from. Selecting the right treatment and attenuation components then turns that baseline into on-site performance.
Responsibility for effective and sustainable water management is shared across disciplines including policy, planning and engineering, and collaboration with specialists in water management can speed adoption of current innovations and ensure effective implementation. By treating water with the collect, clean, hold, reuse method, projects can deliver resilient, multifunctional systems rather than single-purpose installations.
Russell Palmer is National Business Development Manager at ACO Technologies, a sustainable surface water management systems specialist.
Image: Chris Robert / Unsplash
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