Sustainable drainage systems (SuDS for short) encompass a range of techniques for holistically managing water runoff onsite to reduce the quantity, and increase the quality, of surface water that drains into sewers from a development. A general SuDS definition is that it mimics natural systems, and differs from traditional drainage in aiming to manage rain close to where it falls. Not only do these sustainable drainage systems reduce the burden on our sewerage system, they can also help wildlife to thrive in urban areas, with many of the drainage systems being intrinsically wildlife friendly.
So what is the meaning of a SuDS drainage plan in practice? Sustainable drainage systems aim to reduce the amount of runoff from a site. Key to this is to slow the flow of water, to allow it to infiltrate into the ground. Living roofs, soakaways, rills and permeable surfaces are all important for this and so are cornerstones of SuDS drainage. Swales – broad, shallow channels that are often full of plant life – are also important, and can be used to store and/or convey runoff and remove pollutants.
Slowing the flow of water allows it to be taken up and transpired by vegetation, and constructed wetlands and ponds ensure plants aid with the uptake of water and help in cleaning polluted runoff. Such water purification is an important part of the SuDS meaning. Purification systems in the form of ponds and marshes also allow for water to be stored before it is released into watercourses, ensuring that the risk of flash flooding is reduced. As you can imagine, enhancing a development with living roofs, ponds and wetlands not only helps attract wildlife back into the area, but also adds amenity more generally, making the site more attractive to those living and working in the area.
By taking into account amenity and water quality as well as flood risk, SuDS drainage can allow developers to address multiple requirements in one, whereby streamlining the pre-application planning process. SuDS drainage may also be able to assist new development to be undertaken in areas where the existing sewers are at or close to capacity, as the systems aim to reduce runoff to sewers wherever possible.
Not all SuDS techniques are applicable to all sites and the SuDS strategy defines what processes are applicable to a specific development. For more in depth information in to your specific type of site or strategy, download the CIRIA SuDS manual.
From the 6th April 2015 it became compulsory for sustainable urban drainage systems to be considered in the planning applications for major developments, and at Ambiental we are able to provide support and guidance in how best to incorporate SuDS into your development. We’ll soon be publishing a blog to tell you all about the policy changes and how they’ll affect your drainage strategy.
If you’d like any more information about Drainage Design and Strategy, feel free to get in touch with one of our expert consultants.