Sustainable drainage enters the mainstream

Mark Manning of SDS looks at how sustainable drainage is finally being seen as a mainstream option in order to shoulder the impact of climate change

The effects of climate change were recently spelled out in no uncertain terms in a watershed report by the Intergovernmental Panel on Climate Change. In it scientists made a last-ditch plea for unprecedented change to stop our planet warming to catastrophic levels. Frequently underestimated compared to the effects of coastal and river flooding however, surface water flooding threatens millions of homes and businesses across the UK. Sustainable Drainage Systems (SuDS) are key to building resilience, and the good news is that they are finally becoming mainstream. In August, there were encouraging results from the Government’s review of how effective including SuDS in the National Planning Policy Framework (NPPF) has been in promoting greater uptake in England. It found that almost 87 per cent of all approved planning applications reviewed included explicit mention of SuDS. For architects involved in commercial or housing schemes, the consideration should no longer be whether to include SuDS. Instead the question is, what will constitute a great design? Published in July, the revised NPPF added a requirement for SuDS to provide, where possible, ‘multifunctional’ benefits. Instead of just being a means of getting rid of excess water, drainage becomes an opportunity to reuse or recycle it, and to work with nature to create biodiversity or public amenity. The new emphasis reflects wider ambitions to encourage ‘blue green’ infrastructure in urban environments, combining the best that nature can provide with engineering expertise to produce a transformational result.

The SuDS toolbox

Considering the multifunctional benefits of blue green infrastructure should help architects and landscape designers to deliver a ‘management train’ of components that is both attractive and pragmatic. Chosen from a broad SuDS toolbox of natural and engineered features, they can enable one another to work to optimum efficiency. For many years below-ground modular geocellular storage has been a standard means of storing excess surface water robustly to prevent flooding. We are increasingly seeing below-ground storage combined with above-ground public amenities like playing fields or landscaped areas. Using below-ground attenuation can enable a drainage design to incorporate above-ground features like a pond or swale, while achieving the required hydraulic capacity and performance in the space available. By including storage underneath a dry pond or detention basin, an amenity such as a playing field can be provided, designed to flood only infrequently during severe storm events. Alternatively, the underground tank can provide an overflow ensuring that a pond or wetland continues to operate efficiently and wildlife is protected. Greater involvement of Water Companies in the adoption, ownership and creation of new and retrofit SuDS assets is an important positive in building overall infrastructure resilience. This includes important revisions to the Sewers for Adoption 8 manual to be published in Spring 2019. Storage tanks for saving rainwater for re-use can be integrated into domestic or commercial rainwater harvesting systems. Leading water companies are also beginning to offer developers infrastructure charge discounts for including water saving initiatives in developments or avoiding surface water connections to the sewer. This means there’s a good case for promoting rainwater reuse initiatives that combine flood risk management with water saving across sites.

Mark Manning is business development manager at SDS