Louise Page of GreenBlue Urban details how successful collaboration and implementation of multi-functional SuDS interventions can enable specifiers to maximise the benefits of public space in projects
We are all aware of the benefits well-designed green and blue infrastructure can bring, for example in enabling wellbeing by encouraging active travel, bringing communities together, and reducing loneliness, and also improving academic skills, concentration, and behaviour. The need for diverse public green space also needs to be considered, addressing any perceived physical, social, or cultural barriers early on.
The pressure on land for both new developments and in built-up areas is such that reducing the footprint of a scheme is a major factor in the design and delivery of Sustainable Urban Drainage Systems (SuDS) – assemblies of components that intercept stormwater and slow its flow, before it reaches a final attenuation or infiltration point – without reducing the amount of land required for the scheme.
For specifiers, there are both legal, corporate, and economic reasons for finding better and more sustainable ways to manage surface water drainage on new developments. Therefore, the return on the developer’s investment in the land and, given that well-designed SuDS offer additional benefits of amenity and biodiversity, properties protected by SuDS can attract a higher premium. Indeed, some housebuilders have advertised the use of SuDS as a selling point.
Biodiversity Net Gain – by law
The new legislation regarding Biodiversity Net Gain requires developers of new schemes to show that they have increased biodiversity by a minimum of 10%. Coming into effect in 2023, it has helped focus attention on the need for planning for long-term biodiversity. Currently quite a blunt tool – with potentially very ‘biodiverse’ features not given the weighting we think they deserve – it will doubtless result in an improvement in the quality of the landscape. The emphasis on hedgerows and habitat creation gives the opportunity for supporting a wide range of insect and mammal life, and the resulting food chain increase.
Deciding which SuDS interventions to employ and how to combine them to create an effective solution is where collaborative working is key. Developers, local authorities, architects, landscape architects, drainage engineers and utility companies can complement one another by providing problem-solving skills, policy knowledge, creative flair, and site assessment.
SuDS systems can work on practically any scale; from ‘plot-level’ components like rainwater harvesting and green roofs to very large schemes that include several SuDS systems working together. The impressive regeneration scheme in the Grangetown area of Cardiff is an excellent example, and one that we are proud to have played a part in.
A nature-led approach
What options are available? Not all SuDS interventions have to be major. Small-scale features are possible with systems such as bioretention rain gardens, that capture and cleanse stormwater providing amenity and biodiversity to new and existing spaces. Modular systems can be used on a single plot, for example, as a ‘MicroSuDS’ solution, or combined to provide effective flood mitigation on highways or retrofitted into urban environments.
Often the ‘pipe to pond’ approach is used, however the pond could be disproportionately sized, or take up valuable developable land. As a method of intercepting runoff, using trees in ‘Tree Pit’ systems uses the soil they grow in to take up a lot of the strain. They significantly reduce the volume and velocity of water making its way through a SuDS ‘treatment train,’ so any attenuation point at the end of the train can be smaller, or take a different form from the typical pond or swale.
Using good quality tree planting, specifiers can honour their obligations to mitigate developments’ impact, planting into optimal underground environments to offset damage to the environment. Working with bespoke software tools such as i-Tree and CAVAT, specifiers can also assess the limits to which new planting can achieve the specific amount of net gain they require.
Putting nature at the core of a drainage design strategy is key to adding value to development projects. It is possible and cost-effective to combine green and blue infrastructure, at the same time as getting additional biodiversity and saving money on drainage.
The solutions shouldn’t be restricted to holes in the ground. Trees and green infrastructure play an important role in addressing flood risk. All it takes is a bit of fresh, creative thinking and planning.
Louise Page is marketing manager at GreenBlue Urban