Natural capital describes features of the natural environment that provides valuable goods and services to people such as flood risk mitigation, carbon capture and natural woodland, which has valuable benefits for people and the environment. There are many ‘assets’ that make up the natural capital which deliver value for people including soils, wetlands, urban greenspaces and hedgerows. Check out our Jargon Buster to find out more about Natural Capital. There is increasing evidence of the successful use of parks and public open spaces “assets” to fulfil services such as flood risk mitigation in local communities. Here are but a  few examples.

Natural flood mitigation features, such as floodplains, are seen as an important natural capital asset as they deliver a wide range of benefits to people. They regulate flood events by providing space outside of the river channel for flood water to occupy, they store carbon deep into their soil and support large amount of biodiversity. Great examples can be found in the Chimney Meadows National Nature Reserve, the North Meadow National Nature Reserve, and the Nene Valley Nature Improvement Area.

Flood risk is a combination of the probability and the potential consequences of flooding. The probability of flood events tend to be described as 1 in 50-year to 1 in 100-year events. A 1 in 50-year flood has a 2% probably of occurring in any one year. The consequences of a flood depends on 2 factors, exposure, and vulnerability. The consequences of a flood will be less severe in an areas with very few people who are able to evacuate quickly and easily, whereas flooding in an area with lots of people who have difficulty with evacuation is likely to have more serious consequences.

Sustainable drainage system (SuDS) are used to mitigate and manage the risks of flooding by managing rainfall through the replication of the natural process. SuDS prevent many problems cause by surface water runoff from development sites and reduce the of large among of water flow. SuDS manage the flooding and pollution aspects of drainable and ensure that the community and wildlife are considered in the design. They delivery efficiently and effectively across four different criteria:

• Quantity (reduce the risk of erosion and flooding)
• Quality (prevent and treat pollution)
• Amenity (provide visual and community benefits)
• Biodiversity (enhance and create habitats for wildlife)

The following case studies below provide an evidence base to support the implementation of SuDS and the multiple use benefits parks and open spaces can provide:

Lamb Drive, Cambourne

As part of the FLOWS project (Living with Flood Risk in a Changing Climate), Lamb Drive development, a residential development with 35 houses on a 2.5 hectare site, integrated a number of SuDS features into the development design. The aim of the site was to show how SuDS are a practical and innovative sustainable water management technique on a new development and how to incorporate SuDS and property flood resilience and resistance. The development built swales – a series of shallow open channels which slow down the flow of water and make sure that the water continues to be treated – to contain the majority of access water from the site. The also built ‘detention basins’ which are depressions in areas of open space to help flow the water runoff rate and temporarily store water on a short-term basis during extreme events. Finally, bicycle sheds were fitted with green roofs, again to reduce and treat runoff. The impact was a significant reduction in peak flows of water, improved quality of water discharge from the nature filtration, and greater biodiversity. In addition, the capital and maintenance costs were much lower compared to the cost of conventional pipe drainage, the open spaces around homes was valued more highly where SuDS features were present, and the features added to the visual quality of the development, which residents appreciated and said added value to the development.

Red Hell Primary School, Worcester

Another example is Red Hill Primary School, Worcester. The school site is 2 hectares in size and is bounded by a road, railway line and domestic gardens. There is also a small woodland area on the northern boundary. With the new SuDS design, including a detention basin and swale maze, the runoff would go into a new storm sewer. The woodland and detention basin create sufficient storage space for excess water. The swale maze built between the trees created an amenity feature and delivered water to trees. Run-off water from the car park is treated via permeable paving, which stores and sufficiently treats water. Swales, filter strips, and basins all act to treat the water before releasing it to the wildlife pond then the storm sewer. Finally, the pupils could enjoy playing in the swales maze and learning about how SuDS drain sites work.

Overall, we can see sustainable drainage features can not only deal with drainage solutions on a development site, but they can also bring benefits to the communities that they are build in, and the open spaces available to them. They also bring an education element, which can help explain the benefits of these systems to future generations and how they can help the environment in different ways. SuDS reduce flood risk, improve water quality, and increase community engagement, biodiversity and green spaces whilst protecting society from the cost and disruption of flooding.

 

Guest Author: Olivia Jones

We would like to thank Olivia Jones, Cambridgeshire County Council Flood Risk Trainee, who briefly joined the Future Parks team as part of her trainee programme and produced for us this article.