What are the benefits of Sustainable Drainage Systems (SuDS)?
What are SuDS?
Sustainable drainage systems (SuDS) are drainage solutions that provide an alternative to the direct channelling of surface water through networks of pipes and sewers to nearby watercourses. The use of SuDS can reduce the risks and impacts of surface water flooding, improve water quality, and enhance the amenity and biodiversity value of the environment. Furthermore, rising rates of population growth and urbanisation and the impacts of climate change mean the need for sustainable natural management systems such as SuDS is likely to increase in the future.
How do SuDS work?
In natural environments, river levels are maintained by high rates of infiltration into soil and bedrock, and surface runoff is reduced due to high rates of interception and evaporation by vegetation. Denser vegetation also has greater capacity to store rainwater, which further reduces risks associated with flooding.
In urban environments, impermeable surfaces such as concrete and tarmac can reduce natural infiltration to soil and bedrock. Instead, man made channels such as pipes and culverts divert surface water to local water courses. This increased runoff can lead to downstream flooding and deterioration of water quality if foul sewers are overwhelmed by surface water.
What do SuDS look like?
SuDS aim to alleviate these problems by storing and filtering rainwater more effectively. Some techniques include:
Storing or re-using surface water by intercepting run-off water on roofs, leading to water storage and subsequent evapotranspiration e.g. green roofs.
Using retention systems to delay the discharge of surface water to watercourses, such as retention ponds or wetlands.
Improving water quality by using vegetated swales or filter trenches, which remove pollutants from surface water prior to discharge to watercourses or aquifers.
Permeable paving blocks, which have uneven edges that create gaps between the blocks, allow water to flow through them and into the ground below. Some examples of permeable paving are shown here:
The importance of ground properties
Underlying soil and rock conditions play an important role in determining the effectiveness of SuDS, as underlying ground conditions need to be permeable and free draining for many of these systems to operate effectively. Sands and gravels, for example, have high storage capacity for groundwater, however silts, clays and igneous rocks have lower permeability and therefore offer lower storage capacity.
How do Urban Designers use SuDS?
Designers hoping to use SuDS on a development site need to be aware of several factors which can affect their suitability, for example the existence of previous buildings and structures, details of the ground’s permeability, nearby flood risks or flood zones, and details of possible ground contamination. Expert consultation and the use of geological data and Geographical Information Systems can therefore be valuable tools in the design process which can help to avoid costly implications later in the development process.
With early thought, careful planning and due diligence, SuDS can be incorporated into urban designs leading to an increase in the appeal of a development and in benefits to both people and the environment.
Developers and designers hoping to incorporate SuDS into their designs should consult this handy SuDS guide for developers https://www.bgs.ac.uk/download/guide-to-suds-for-developers/
Further useful information can be found at www.bgs.ac.uk/geology-projects/suds/
Graeme, thank you for your insightful write up on SUDS. In our urban design project, I and Kit decided to use Urban swales and SUDS for water collection. The mound on her site presented an unusual opportunity to harvest rainwater and use for the allotments on my site. It is important to note that SUDS are not new concepts, and despite being implemented widely they do not always function perfectly. To pre-empt their malfunction, we must understand how they sit in the drainage context.
The first issue with SUDS is because of how advanced the technology is. This shift from conventional practices to one that many practitioners are not familiar with means there is a higher risk of failure (Brown and Farrelly, 2009). Another issue arising from installing SUDS is the difficulty of integration with existing systems. Unlike conventional drainage systems (buried underground), SUDS are usually above ground and require features from existing urban systems that are usually not present (Hoang and Fenner, 2016). Finally, because of their organisational complexity, they usually require more integrated decision making between different professionals. This added layer of decision-making complexity allow room for more errors as well. These are only a few of the hurdles we face in developing a more sustainable world.
References
Brown R. R. Farrelly M. A. 2009 Delivering sustainable urban water management: a review of the hurdles we face. Water Science and Technology 59 (5), 839–846.
Hoang, L. and Fenner, R., 2015. System interactions of stormwater management using sustainable urban drainage systems and green infrastructure. Urban Water Journal, 13(7), pp.739-758.
It was a very interesting blog and gave me a better understanding of the benefits of Sustainable Drainage Systems (SuDS). Not only does it explain what SUDS is, but it also gives a detailed description of how the system works. It is already important for the city and how it will develop in the future.
After reading the article, I think the main considerations are water quality, quantity and the recreational value of surface water comfort and amenity in the urban environment. And the SUDS system has risen from a traditional discharge-focused drainage system to a sustainable drainage system that maintains a high level of virtuous water circulation, taking into account the water quality and quantity of runoff, landscape potential and ecological value in its design.
In future designs, I think this is also very much something to learn from and take note of. From the original optimisation of urban drainage facilities only to the optimisation of the entire regional water system, not only rainwater but also urban wastewater and recycled water should be taken into account to improve the overall urban water cycle through the adoption of comprehensive measures.
Graeme, this blog is very insightful of the benefits of sustainable drainage systems (SuDs). Sustainable drainage systems are essential in any development nowadays. Working with natural systems and of neighbourhood design will become key over the next generation of shaping neighbourhood (Barton et at, 2021). My questions are can rainwater be used in any other way?
In Gabie and my recent design, the former Chandless estate. We established permeable paving, green and brown roofs, roadside slow drainage with plants, and SuDs Pond that is connected to another sustainable drainage system, thereby enhancing the existing infrastructure. I also advocated rainwater can be treated as goods and services like fresh water, food, fuel and waste amelioration. Rain harvesting could also contribute to other activity such as allotments and play where people of all ages can benefit from the use. Management of water as you mentioned such as vegetation or gravel filter could help minimise contamination especially if children were playing (Planet Earth, 2010).
For incorporating SuDs and rainwater play, in housing details you could look at spourts, rain chains, cascades, gutters or channels or rills along the ground.
Reference:
Barton, H., Grant, M. & Guise, R. (2021) Shaping Neighbourhood: For Local Health and Global Sustainability. London: Routledge. 3rd Edition.
Planet Earth (2010) A ‘How to’ Guide Play with Rainwater and Sustainable Drainage. Available at: https://londonplay.org.uk/wp-content/uploads/2020/06/Sustainable_drainage_and_play_with_rainwater_low_res.pdf (Accessed: 25th May 2022).