The biodiversity advantage:  Exploring the benefits of addressing BNG in SuDS solutions

We can’t escape the fact that in today’s urban environments, managing rainwater runoff is crucial. Sustainable Drainage Systems (SuDS) are intended to play a vital role in this, addressing both water quality and flood risks.

However, there is a wider requirement to SuDS that is perhaps less well known. The need to respond to the nature crisis has prompted legislation that requires SuDS to enhance biodiversity, as well as provide amenity and water quality benefits. Importantly, integrating space for other creatures in SuDS also benefits people, creating harmonious and sustainable living environments.

As consumer and legislative focus continues to shift towards biodiversity restoration, projects that address this effectively will be seen in a favourable light.

Benefits of Biodiversity in SuDS:

• Water Quality Improvement:

As material is washed from a surface, the initial 5mm of rainwater often contains the most pollutants. Diverse plant and animal life in SuDS can naturally filter these pollutants. Microbial activity in soils, enhanced by plant diversity, can effectively break down contaminants including hydrocarbons. Rich biodiversity is key as research shows that microbial diversity directly correlates with plant diversity, leading to better pollutant breakdown and cleaner water.

• Flood Control:

Many flood events stem from water running off impermeable surfaces. Biodiverse planting schemes within SuDS help absorb and retain rainwater, reducing flood risks. Plants add structure, including stems, leaves and flowers, creating physical barriers that slow rainwater flow and allows more time for infiltration. Plant roots penetrate deep into the soil, reducing compaction and creating pathways for water percolation. Additionally, plants promote evapotranspiration, returning water to the air and reducing the overall volume within the drainage system. Plant diversity creates a healthy soil balance, rich in organic matter and complex in structure, all helping to absorb large rainwater volumes, alleviating pressure on drainage systems during heavy rainfall.

• Amenity:

Time spent within the natural environment is proven to boost our immune systems, mental health and recovery from illness. In educational settings, access to nature enhances creativity and productivity and wildlife-rich greenspaces foster social interaction, creating cohesive communities and a strong sense of place. It is clear that a connection to biodiversity is good for us and yet only half of us living in the UK have easy access to nature. Investment in nature also yields financial returns, with leafy areas attracting business and enhancing property values.

• Habitat Creation:

We depend on the natural world in so many ways, from the oxygen we breath and the food we eat to carbon sequestration and limiting the effects of extreme heat, the abundance of plant and animal life is core to our survival on planet earth. Biodiversity decline severely threatens these benefits, but SuDS can go some way to reverse this trend. By supporting a richness in soil health and plant diversity sustainable drainage systems can encourage a wealth of insects, invertebrates and microbial life which in turn feed a wide variety of birds, mammals and other wildlife, creating a more resilient ecosystem. And of course, this explosion of colour, scent and buzz creates attractive places where we feel energised and want to spend time.

 

Biodiversity-Friendly SuDS Designs:

It goes without saying that the drainage and biodiversity needs of a project will vary from site-to-site and there is no ‘one-size-fits-all’ answer. An ecological survey early in the planning stages can help determine which solution suits the project.

• Green Roofs:

Ideal for dense urban areas with limited space, green roofs provide lush, green spaces that maximise public use. These areas are often stressed due to lack of water or nutrients but this can promote rare species including orchids and solitary bees.

• Rain Gardens:

Designed to capture roof runoff, rain gardens can be filled with native wildflowers to attract pollinators. Multifunctional units like those from BioScapes help to address all aspects of SuDS compliance and support a diverse range of species from hedgehogs to hoverflies.

• Bioswales:

Functioning as natural filters, bioswales can encourage water infiltration and slow flows. Diverse plant life within bioswales further enhances their ability to manage water flow and provide improvements in water quality.

• Constructed Wetlands:

Ponds and marshy areas mimic natural ecosystems, providing habitats for a variety of wildlife, from amphibians and aquatic invertebrates to birds like ducks and kingfishers.

Challenges and Considerations:

Incorporating a SuDS solution into a project is just the beginning, delivering the desired net gain requires commitment in the long term.

• Planning and Design:

Local ecology must be considered at the earliest stage of the design process to retain important features, incorporate habitat corridors and select native plants beneficial to local fauna.

• Maintenance:

Selecting low-maintenance plants that thrive in both wet and dry conditions can be beneficial. While some management is necessary, overly manicured areas can lose biodiversity, so a careful balance must be struck.

• Public Awareness:

Developing biodiverse SuDS that people enjoy encourages community ownership and care. By involving members of the public in the design process we can influence their understanding of the benefits, increasing the likelihood that these spaces are interacted with and maintained.

It’s clear that SuDS can offer multiple benefits, maximising use of space, managing urban drainage, promoting a healthy environment and fostering vibrant communities. It’s time to embrace biodiversity in SuDS and consider how your projects can best incorporate these elements.

BioScapes provides a range of SuDS units designed to support wildlife, encouraging wider adoption of biodiversity-friendly solutions. Working together, we can generate sustainable, biodiverse urban environments. To arrange a free biodiversity audit with one of our ecology experts, email consulting@bioscapes.co.uk

Author: Terry Smithson BSc in Zoology, MSc in Ecology

Terry is BioScapes’ in-house ecologist and Head of Nature Based Solutions. Terry has worked in the nature conservation sector for over 25 years. His expertise has helped shape the design of BioScapes products to ensure that they maximise the protection of our ecosystem. Terry also provides a consultative service for customers who are looking to do the same.