The Use of Sustainable Drainage Systems (SuDS) in Cambridgeshire
Sustainable Drainage Systems (SuDS) have been an essential part of water management in Cambridgeshire for a number of years. And with Cambridge City Council winning two Landscape Institute awards for its sustainable drainage design and adoption guide, it’s fair to say the county has a strong reputation when it comes to sustainability. Here, we take a closer look at SUDs and the impact they are having across Cambridgeshire.
What are Sustainable Drainage Systems?
SuDs replace conventional infrastructure such as pipes and tanks by mimicking natural drainage processes. They manage to capture rainfall and manage surface water runoff more sustainably, by allowing as much water as possible to evaporate or soak into the ground. Any remaining water is then directed to the nearest watercourse where it is released at a measured rate to prevent flooding.
Why Are SuDS Used in Cambridgeshire?
Put simply, water defines much of the Cambridgeshire landscape. The fenlands are flat and low-lying – interspersed with lakes, dykes and rivers such as the Nene – while the tributaries of the River Cam dissipate into water meadows in the surrounding villages. The saturated environment leaves these protected areas of natural beauty liable to flooding.
Cambridge itself is full of historic wetlands like Coe Fen and Sheep’s Green, and of course the renowned Backs. Water runs alongside the streets, with the unique Runnels along Trumpington Street leading into Hobson’s conduit.
In 2017, the city was named the UK’s fastest-growing economy and has been designated as one of four national growth areas. In light of this, it is imperative that Cambridge is developed in a sustainable manner to ensure the character of the historic waterways and wetlands are maintained. SuDS offer a solution, allowing for the water from new developments to be managed in an environmentally friendly and sustainable way.
The Benefits of SuDS
Whilst reducing the risk of flooding is arguably the key benefit of SuDS, they also deliver advantages in a number of other areas:
- Reduces the Impacts of Climate Change: With the planet set for increased rainfall and resultant surface water, SuDS are a forward-thinking solution to manage more extreme weather. Moreover, by managing surface run-off, SUDs encourage passive cooling which will help with temperature increases caused by global warming.
- Easier to Repair: In comparison to the underground pipe systems they replace, SuDS are quicker, easier, and cheaper to repair as they are at street level and don’t require infrastructure.
- Removes Pollutants: As water flows through soil, the metal ions and hydrocarbons it has picked up in developments are partially filtered out, so the water is cleaner when it enters rivers and streams.
- Encourages Wildlife: Not only is cleaner water more beneficial to wildlife, but SuDS are often planted with nectar-rich plants to encourage butterflies and bumble bees to the area.
Examples of Common Systems
There are a diverse range of Sustainable Drainage Systems being used across Cambridgeshire in both urban and rural areas.
- Green roofs: As the name suggests, a green roof is a roof with plants and other greenery growing on it, which allows for the storage and treatment of rainwater. Green roofs also enhance the aesthetic value and biodiversity of buildings.
- Permeable Paving: Used in various parts of Cambridgeshire, permeable paving allows surface water to soak into the ground through voids in the paving. Water can soak straight into the soil or be stored underneath the paving before being safely conveyed from the site. The paving can also filter water as it flows through.
- Attenuation Basins: Open, flat and dry areas of grass that can become saturated and used to store water during heavy rainfall. The basins will often have a shallow depression to maximise the storage area. The topsoil has to be sufficiently permeable for the water to lie just underneath the surface. In Eddington, a large scale basin has been incorporated into the natural landscape of the area.
- Swales and Filter Strips: Both of these systems control how water travels from its source. Swales are shallow channels that are used to collect and move water towards a river, whilst filter strips are areas of sloping grass one to two metres wide that allow water to move into the topsoil of a swale. At Loves Farm in St Neots, swales are used to direct surface water away from the new development.
- Filter Drains: Gravel-filled trenches that collect water, remove silt and treat pollution. Underneath the gravel is a perforated pipe which collects the water and draws it towards its destination; there is also a layer of geotextile which traps silt to stop it clogging the gravel. They are often found beside hard surfaces such as roads.
- Soakaways: Sitting just below the ground, soakaway systems are typically used to collect wastewater or rainwater and let it soak back into the earth, preventing a build-up of water on the surface. However, they can also be used to store excess rainwater during heavy rainfall.
- Rainwater Harvesting Systems: Whether it is above-ground or underground, these systems encourage the re-use of water, reducing the impact on climate change as well as your water bill. In fact, it’s estimated that a rainwater harvesting system can save you up to 50% of your metered water costs.