8 February 2016
Article by Elfyn Henderson, National Assembly for Wales Research Service
The Welsh Government published interim non-statutory standards for sustainable drainage (SuDS) in Wales in December 2015:
What is sustainable drainage?
SuDS – or sustainable drainage systems – are designed to reduce the impact of development on surface water drainage by working with natural processes to drain away surface water run-off. This is done by collecting, storing, and cleaning water before allowing it to be released slowly back into the environment.
The SuDS approach is different from conventional drainage systems which are based on underground pipes to move rainwater away from properties as quickly as possible. Conventional systems can contribute to increased risk of flooding, pollution and groundwater contamination.
The benefits of SuDS include reducing the amount of water contaminated with sewage that is pumped for treatment, and reducing the risk of overflows and flooding. Depending on how they are designed, SuDS can also improve urban design quality, create public green space, increase biodiversity, and improve air quality and noise buffering.
You can read more about SuDS on the SuDS Wales website.
What do the standards cover?
The standards cover the design, construction, operation and maintenance of SuDS serving new developments of more than one house or larger than 300m2 floor space. They provide information for designers, property developers, local authorities and other interested parties, such as sewerage undertakers and Natural Resources Wales (NRW).
The standards include a number of principles that should underpin how SuDS are designed. They also include criteria for prioritising the choice of run-off destination, minimum design criteria and set out how SuDS should be constructed, maintained and operated. The design principles include the following:
- Manage water on or close to the surface and as close to the source of the runoff as possible.
- Treat rainfall as a valuable natural resource.
- Ensure pollution is prevented at source, rather than relying on the drainage system to treat or intercept it.
- Manage rainfall to help protect people from increased flood risk, and to help protect the environment from damage resulting from changes in flow rates, patterns and sediment movement caused by the development.
- Take account of likely future pressures on flood risk, the environment and water resources such as climate change and urban creep.
- Maximise the benefits for amenity and biodiversity.
- Make the best use of available land through multifunctional use of public space and the public realm.
- Avoid the need for pumping where possible.Developers are expected to demonstrate that they have complied with the standards when submitting planning applications.
What happens next?
The Flood and Water Management Act 2010 (Schedule 3), which has not been commenced in Wales (or England), requires new developments to include SuDS features that comply with national standards.
The interim standards have been published on an advisory basis so that the relevant parties (designers, developers, local authorities etc) can demonstrate that they have taken account of the Welsh Government’s policy on Development and Flood Risk and Nature Conservation and Planning. They have also been published so they can be piloted and, if necessary, revised should Welsh Ministers decide to make them statutory.
The Welsh Government’s approach to SuDS is set out in its Water Strategy for Wales.
Examples of SuDS in Wales
Greener Grangetown, Cardiff
The Greener Grangetown scheme is a partnership between Cardiff City Council, Dŵr Cymru and NRW. The scheme proposes to collect, clean and divert rainwater directly into the River Taff, instead of pumping it eight miles through the Vale of Glamorgan to the sea as is currently the case. The scheme is to include planted areas that will help absorb rainwater, increase biodiversity and provide public green space.
NRW has produced a Greener Grangetown Video:
You can read more on the Greener Grangetown blog.
Dŵr Cymru is investing around £80million in a number of RainScape projects in Wales up to 2020. Projects in Llanelli have been developed to address issues with the volume of rainwater entering sewers during periods of heavy rainfall. One project involved dealing with surface water issues in a primary school by introducing a pond, a swale, planters, permeable paving, water butts and an outdoor educational area.
You can read more about Dŵr Cymru’s projects on its RainScape website.