Sustainable Urban Drainage Systems (SUDS): a proactive approach to reducing surface flooding
Climate change, urbanisation and population increase are the combined source of multiple issues within the UK, one of them being the increasing rate of flood events and damage caused by surface water flooding1. Caused by the overflowing of drainage systems unable to cope with heavy rainfall, rather than draining away, the rainwater gathers at the surface causing flooding2. Without considerable change to the conventional drainage methods used currently, the rate will only continue to rise. The use of sustainable drainage systems (SUDS) could be a good method to slow down the rise in flooding.
In 2017 the UK government pledged to build 1 million new homes by 2020 and a further 500,000 by 20223. This has been pledged in order to meet estimated population growth within the UK, predicted to increase by 3.6 million in the next 10 years, with 54% of that increase down to net migration4.
This predicted growth of housing will add increasing pressure to the drainage infrastructure already in place as new build developments are being connected to existing drainage systems rather than new systems being designed5. The current urban drainage infrastructure often cannot cope with the increase in capacity due to these changes in usage6 and this can lead to an increase in surface water floods events. Furthermore, rapid urbanisation has seen an increase of impermeable surfaces, decreasing the available surface for natural drainage and retention of rainfall. An example being between 1999 and 2007, London saw a 26% increase of hard surfacing of gardens1. This can lead to surface runoff and further increases the pressure on drainage and sewer systems beyond their capacity to cope, inducing surface water flooding7.
The current cost in damages caused by surface water flooding is over £300 million each year1. The evidence shows that the frequency of storm and rain events that cause flooding to occur has quadrupled since 1980 and doubled in the past 14 years since 20048 due to climate change. If no significant changes are made in order to slow down the rise and severity of these events, then it is estimated that the cost of damages could rise by 40% by the 2050s1.
The risk of surface water flooding across England has been mapped by the Environment Agency. Groundsure uses this mapping with other data to offer a more property specific search, giving further information regarding surface water flooding and also the other common types of flooding. More information about this can be found through our website by selecting the Flood Risk category on the left.
Making the change to SUDS
When the increase in housing and urban spaces is combined with the growing rate of events caused by climate change then more and more flooding will occur if drainage systems remain the same. A change that could be more widely implemented that can help to reduce the impact surface water flooding will have in the future is the use of SUDS. SUDs come in variety of forms, but unlike the conventional and outdated drainage systems used in urban areas currently, focus on slowing down and reducing the amount of surface water runoff, as well as encouraging natural infiltration of water. By slowing down the rate at which water reaches areas often at risk of flooding, the peak of rain and storm events won’t be as high, therefore reducing the impact urbanisation has on surface water flooding.
The multiple methods that can be used as sustainable drainage methods, include:
● Green Roofs – by retaining rainwater in the vegetation and soil layer, they reduce storm water runoff, decreasing the risk of flooding, whilst also providing additional benefits such as providing insulation, thus reducing heating costs in homes and creating a biodiversity stepping stone9, as well as a green space in compact urban areas. They have multiple applications, from bus shelters, small residential homes to large office buildings.
● Permeable Paving – unlike traditional concrete, this is made from a porous material allowing water to infiltrate through it rather than along the surface of it. Therefore, this kind of paving contributes to decreasing the overall surface runoff from rain events and reducing the risk and severity of flooding10.
● Retention Ponds acts to hold floodwater during a storm event with slow release after the risk of flooding has decreased. Furthermore, such ponds can provide a biodiversity hot spot as well as acting as an open space for public access11, which can have additional health and well-being benefits.
These are just a few options that can be implemented to reduce the increasing rate of surface water flooding within the UK. These methods, along with others, will have to be considered in the future in order to sustainably maintain the growth of UK housing whilst mitigating the local effects of climate change.
1. Holmes (2018) Committee on Climate Change. Blogs. Available from: https://www.theccc.org.uk/2018/07/30/first-the-heat-then-the-rain-the-problem-of-surface-water-flooding-in-england/ [Accessed 30 November 2018].
2. Environment Agency (2018) River maintenance, flooding and coastal erosion. Available from: https://www.gov.uk/government/news/surface-water-the-biggest-flood-risk-of-all [Accessed 05 December 2018].3.
3. Parliament. House of Commons (2018) Tackling the under-supply of housing in England. London: (HC 2018 07671).
4. Office for National Statistics (2009) National population projections. Available from: https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationprojections/bulletins/nationalpopulationprojections/2016basedstatisticalbulletin [Accessed 30 November 2018].
5. Wildon UK (2017) News. Available from: http://www.wildonuk.co.uk/news/new-build-homes-in-the-uk-putting-pressure-on-drainage/ [Accessed 30 November 2018].
6. Davis, M. and Naumann, S. (2017) Making the Case for Sustainable Urban Drainage Systems as a Nature-based Solution to Urban Flooding. Nature-based Solutions to Climate Change Adaptation in Urban Areas [online]., pp. 123-137. [Accessed 30 November 2018].
7. Swan, A. (2010) How Increased Urbanisation Has Induced Flooding Problems in the Uk: A Lesson For African Cities?. Physics and Chemistry of the Earth, Parts A/b/c [online]. 35, pp. 643-647. [Accessed 30 November 2018].
8. ScienceDaily (2018) Science News. Available from: https://www.sciencedaily.com/releases/2018/03/180321130859.htm [Accessed 04 December 2018].
9. Berndtsson, J.C. (2010) Green Roof Performance Towards Management of Runoff Water Quantity and Quality: A Review. Ecological Engineering [online]. 36 (4), pp. 351-360. [Accessed 05 December 2018].
10. How Stuff Works (2018) Green Science. Available from: https://science.howstuffworks.com/environmental/green-science/green-pavement1.htm [Accessed 05 December 2018].
11. Susdrain (2018) Retention Ponds. Available from: https://www.susdrain.org/delivering-suds/using-suds/suds-components/retention_and_detention/retention_ponds.html [Accessed 05 December 2018].