Samantha Hursey of Meadfleet Open Space Management discusses the practicalities of maintaining SuDS and how they can bring amenity to new housing developments.
Sustainable Drainage Systems or SuDS, not only play a key role on residential developments in mitigating the risks of flooding, but they also offer ecological and amenity value. Ideally, they will be maintained to maximise all three benefits, making them a key feature in new residential schemes.
What are SuDS?
SuDS mitigate the impact of new developments on local drainage to reduce the risk of flooding. They also help improve water quality and support biodiversity. SuDS simulate natural drainage to manage the risks of flooding and pollution caused by urban surface runoff. Wherever possible they should also provide environmental enhancements and contribute to the amenity value of an area.
Examples of common SuDS features include attenuation ponds, also known as balancing ponds, which are designed to hold water and slow down the flow of stormwater runoff particularly during periods of heavy rain. Swales are another frequently used mechanism on a housing development to help control urban runoff. They are shallow channels with gentle slopes that collect and move water. Swales also assist in the improvement of water quality by removing pollutants through infiltration.
Another example is permeable paving which can be used on roadways, drives and patios and can often drain double their surface area, allowing for more water to be stored and infiltrated, preventing it from directly reaching a watercourse. Permeable paving is beneficial in that it does not require any additional space and serves a dual function while being easy to maintain.
Why are SuDS important?
With increasing extreme weather events and the likelihood of warmer and wetter weather in the coming years, it is vital that housing developments do not place added pressure on existing drainage systems. SuDS provide a solution to mitigate flooding and reduce water pollution, and it is likely that they will become a compulsory feature on all new developments.
Not only do sustainable drainage systems provide practical solutions to mitigate flooding, they also offer other benefits as previously mentioned including biodiversity enhancement, another key focus of the housebuilding industry with the introduction of Biodiversity Net Gain legislation earlier this year.
What are the challenges of maintaining SuDS?
When designed and built following best practice guidelines, SuDS do not require a complex day-to-day maintenance programme. An ongoing schedule of works must be followed to ensure features such as inlets and outlets are always kept clear to ensure water can flow without obstruction.
Regular maintenance and inspections must be combined with less frequent tasks such as silt removal and vegetation management. Vegetation must be managed carefully in and around SuDS with invasive species identified and removed. Maintenance regimes must consider the potential presence of wildlife and be conducted at the most appropriate time of year to reduce disruption to any species that may be present.
While day-to-day management and maintenance of SuDS can be straightforward, there are likely to be ad hoc tasks that require specialist technical and ecological expertise.
What are the biodiversity benefits of SuDS?
SuDS have multiple benefits for wildlife. Traditional drainage can reduce the amount of water for plants and animals while also allowing pollutants to enter waterways. SuDS can help increase the amount of water and suitable habitats available for wildlife. Successful sustainable drainage systems will provide food, shelter and breeding opportunities for birds, mammals, amphibians, and invertebrates.
Structure is a key factor for optimal biodiversity value. Providing a variety of grass lengths for example and leaving some areas uncut or cut on rotation enhances structural diversity which will benefit varied species who will use the grasses in different ways. Longer grasses offer a suitable location for the eggs and larvae of some insects to remain over the winter months. Reptiles and amphibians will use longer grass as cover and search it for insects.
Marginal wetland vegetation is ideal to be kept long as it helps increase humidity creating preferable conditions for wildlife.
How do SuDS improve amenity value?
SuDs can provide benefits to new housing developments that contribute to the amenity value of an area. Many SuDS features are dual purpose, for example play areas may double as detention basins and roadways may incorporate permeable paving, thus maximising the available space on the development while not impacting the aesthetics.
Carefully managed SuDS such as basins and swales can be visually pleasing, adding variety to a landscape while attracting a range of wildlife, from insects such as bees, moths and butterflies to birds, newts, and water voles. Access to well-maintained green spaces and nature are proven to support both physical and mental wellbeing, and open spaces that include a variety of features are thought to have the greatest impact in this respect.
Through careful management, green SuDS with beneficial planting can contribute to also help cool urban areas and remove pollutants from the air.
SuDS can become a key feature of a development with community involvement. Adding bird feeders, insect hotels and wildlife shelters on or adjacent to them helps maximise their appeal to residents and signage can be used to educate on the benefits of these features. Activities such as wildlife walks and bug hunts can further engage residents.
What are the key things to consider when designing & implementing SuDS?
Collaboration by all parties is useful to ensure the successful design and implementation of SuDS features. Designers and housebuilders must consider future practicalities of ongoing maintenance requirements. Ensuring the SuDS are designed to allow the elements to be suitably accessed and easily maintained on a regular basis are key to the successful management of drainage features.
Housebuilders must consider the appropriate solutions for the ongoing specialist management of sustainable drainage features. Options include management companies who will take long term responsibility and provide a robust inspection and maintenance process to meet planning approval and the ongoing needs of SuDS features. Organisations that take an objective approach, taking into account best practice and managing SuDS for optimum effectiveness as well as biodiversity and amenity value should be sought for the long-term success of SuDS features and the legacy of the development.
Samantha Hursey is operations director at Meadfleet Open Space Management