Surface water run-off from housing, industry, and other urban development is recognised as a primary contributor to flooding. The built environment often includes large impermeable surface areas such as roofs, driveways and roads, which cause rainwater to run off into highway drains, contributing to flooding of other parts of the drainage network.
Sustainable drainage systems utilise or mimic natural landscape features to slow the flow of rainwater into drains, gutters and rivers. This can help to prevent them from getting overwhelmed during heavy rainfall, mitigating the local flood risk.
SuDS complement other measures such as engineered flood defences, rural natural flood management and property level protection in a holistic approach to flood risk management.
Examples of SuDS
SuDS can be introduced in virtually any outdoor space from small gardens to large developments. They can be as simple as swapping a concrete driveway for a permeable one or as complex as an integrated landscaping scheme incorporating a range of different measures.
Some examples of SuDS include:
- Green roofs - roofs that are covered with vegetation
- Water butts - leave tap open to increase storage capacity
- Raised planters - usually connected to a downpipe to collect rainwater
- Permeable paving - e.g. gravel, pavers without mortar and grass reinforcement
- Retention ponds - open areas of shallow water, which provide temporary storage for excess water
- Detention basins - open, flat areas of grass that are usually dry, except after heavy rainfall
- Swales - shallow channels designed to store runoff
Benefits of SuDS
As well as reducing the risk of flooding from development, sustainable drainage systems can also:
- Benefit local ecosystems
- Reduce pollution
- Capture rainwater for reuse
- Improve the look and feel of an outdoor space
- Bring economic benefits to the local area
- Improve the quality of life of people using the space
- Improve mental and physical health of people using the space
- Provide recreational and educational benefits
- Improve water quality
- Reduce costs on projects, when considered early in the design process
SuDS schemes in Calderdale
Many individuals, communities and organisations in Calderdale are already using SuDS in this way. Slow The Flow Calderdale has helped the Mytholmroyd flood wardens to build a green roof for its flood store, creating an attractive feature and doubling up its benefits to the local community.
Slow The Flow and Calder Rivers Trust have built five rain garden planters in the courtyard of Hebden Bridge Town Hall using funding from the People’s Postcode Lottery to demonstrate how SuDS work and encourage visitors to make their own interventions at home.
Yorkshire Water has been running 'Soak it Up' workshops with communities and schools throughout the region, including Scout Road Academy in Mytholmroyd, to encourage residents to think about how small actions can contribute towards the removal of flooding. This video shows a similar installation at Norton Community Primary School in Malton.
There are lots of further examples of local SuDS creations on Slow The Flow’s Case Studies page.
Identifying new opportunities
Slow The Flow has developed an interactive online map, initially in a pilot area of Mytholmroyd, to give geographic detail and specific advice on proposed locations for rural natural flood management NFM) and SuDS. These measures can be adopted by property owners or, with the permission of the landowner, on public or private land. You can view the map here.
Calderdale Council is taking steps to promote the use of sustainable drainage systems in new properties and their associated highway infrastructure. In December 2018 it published its Draft Flood Risk and Drainage Supplementary Planning Guidance (SPG) for use when considering planning applications to supplement and support the Local Plan.
The SPG has now been consulted upon with comments sought from internal and external stakeholders. Feedback from the consultation is being reviewed and the SPG will be updated and submitted alongside the emerging Local Plan.
Interested in installing sustainable drainage systems or finding out more? Slow The Flow has online and printable guides to the general principles of SuDS and their use at home, at work, at school and in public spaces. See: You Can Slow The Flow.
(Images: Slow the Flow Calderdale)