7 minute read
Getting SuDS right for housing
Clearly visible and colourful rain garden in Alcester, Warwickshire. © DSA Environment and Design
Schedule 3 of the Flood and Water Management Act (2010) will be enacted in 2024, providing a framework for the approval and adoption of SuDS in England and, most importantly, it will make SuDS mandatory for new developments.
As a concept, Sustainable Drainage Systems (SuDS) has been around for some time. In the early nineties, I attended a conference in Coventry as a young landscape architect. Bob Bray, then and still the voice of SuDS, was inspiring and encouraged an audience of mostly engineers to embrace a new idea. Instead of guiding stormwater to run unhindered through increasingly large pipes to the river, we should hold it back and ‘slow the flow’.
Bob’s pioneering work in the 1990s, together with that of Tom Liptan in Portland, has paved the way for other great schemes, including interventions like Grey to Green in Sheffield and Greener Grangetown in Cardiff.
Almost 30 years on, what seems to have characterised SuDS in the UK has, for the most part, been small scale. Often these interventions have been highly urban and frequently isolated, instead of joined up. Most schemes of note have been retrofitted. What has been notably lacking (speaking as someone with a position on the Susdrain Awards judges panel) is an ambition for bringing SuDS principles into housing. There are some examples of innovative practice, but local planning authorities are mostly seeing more of the same. Why is this?
Schedule 3 of the Flood and Water Management Act (2010) will be enacted in 2024. It will provide a framework for the approval and adoption of SuDS in England and will make SuDS mandatory for new developments. We could be at a ‘hinge point’.
‘SuDS’ is an unfortunate name for a great thing. Its central notion is that drainage should mimic the way water behaves naturally in the landscape. It is only when the ground’s capacity to absorb the water is exceeded that it drains anywhere. Arguably, this is much better expressed by the Australian term ‘Water Sensitive Urban Design (WSUD)’. What we ought to be trying isn’t drainage: it’s ‘soakage’. In the UK, there is a strong focus on water quantity, primarily because it can be more easily calculated. What we typically see in housing is what urban designer Dr Stefan Kruczkowski calls ‘pipe and pit’. The water is buried, contained and concealed. Flooding is still the biggest driver when it comes to drainage design. Under-drained swales that dry out the ground, for example, demonstrate an imbalanced approach to SuDS, when considering the principle is to achieve natural ‘soakage’.
Water quantity is only one of the main considerations of SuDS schemes, and the enactment of Schedule 3 risks further exacerbating the focus upon it, in order to alleviate the immediate threat of flooding. This could lead to the other vital tenets of a good SuDS scheme being overlooked. It should be the role of landscape architects to look at the challenge of water holistically and demonstrate its value as part of the blue-green network. Housing design tools such as ‘Building for a Healthy Life’ place a strong emphasis on the multiple benefits of blue-green infrastructure. A critical concern of such design should also be an emphasis on amenity value.
The amenity value of SuDS is only loosely defined and there is scope for future work to further evidence this aspect. According to CIRIA’s SuDS Manual, amenity means that SuDS should ‘create and sustain places for people’; this is right up our street as landscape architects. Perhaps, to be counted as fulfilling the requirements of good SuDS design, amenity should deliver on each of the following:
Clear Accessible Playful and Engaging
Clear
Is it apparent, obvious and noticeable? Often SuDS features are at the periphery of the site, especially the ‘attenuation basin’, and the connections into the system are concealed. These places aren’t usually easy to get to or to find.
Accessible
Levels are important. On steeper sites this challenge is only overcome by careful site planning in the early stages. It is not acceptable to exclude disabled users. Paths should be broad and level enough for everyone to enjoy public spaces. Fencing is put in to make a feature, that would otherwise be classed as dangerous, ‘safe’. These things hinder management, among a lot else, and are expensive to install and maintain.
Playful
Any blue-green infrastructure designed as an integral component of a housing area ought to be inherently safe to play in and around. Far too many schemes exhibit a disregard for this component, with permanent water maintained at depth and steeply sided slopes frequently covered in vegetation as to make the hazard invisible.
Naturally all activity carries risk. If the SuDS introduces an unacceptable level of risk, then perhaps it shouldn’t be there in that form, right from the start. Play England guidance asks designers to consider whether the rewards of encouraging children to play naturally outweighs the perceived risk of doing so.
Engaging
Does it contribute to the wider message of water-sensitive design?
I’d argue that the functions of the system should be, whenever practicable, explained. Early work in the nineties in New South Wales was very successful in explaining to residents why creeks and domains had been altered. We’ve had incidences of complaints where, in revealing surface water during storm events, our SuDS has been accused of causing flooding. For many, surface water attenuation is counter intuitive; this is new for a lot of people.
The SuDS scheme at Albion Close in Lincoln dates from 2013 and was adopted by Lincolnshire County Council and Anglian Water in 2017. This eco-development is considered by Lincolnshire to be an excellent example of SuDS. It’s a clear and accessible solution on what is a tight and steeply sloping site. It has a SuDS ‘management train’ that runs from plot to plot to an open and dry basin at the bottom. Lincolnshire use the site as an exemplar in encouraging more developers to follow a SuDS approach.
In 2015, DSA worked with Solihull Council and Bellway Homes on a relatively ordinary housing scheme in North Solihull. The proposal, initially very unpopular locally, provides 50 houses close to the River Cole. It involved the declassification of a grassland nature reserve and the creation of arguably richer habitats. SuDS is provided alongside the existing river, necessitating a series of basins that fill up during periods of high rainfall. Much of the time the basins and swales are empty and merely damp.
Under the leadership of landscape architect Mike Eastwood, Solihull took a bold stance and enabled the basins to be widened and made more extensive but shallower. Rocks, timber posts and seating were introduced as ‘prompts for play’. The Cole Valley path was extended to better connect the site with Babbs Mill and Kingfisher Local Nature Reserves, forming a paved walking circuit. This has created a wetland system where none existed before, arguably conforming to the principles of ‘CAPE’.
There is still a lack of appreciation and understanding that a SuDS approach needs to mimic natural systems and bring people closer to nature. David Attenborough called for our ‘great responsibility’ as landscape architects to be ‘bringing people face to face with the natural world’ on their doorstep. Applying design effort to and prioritising the amenity value of SuDS offers a perfect opportunity to do this.
David Singleton is the Director of DSA Environment and Design. He served as an advisor to CIRIA, co-authored ‘Building for a Healthy Life’ and has given talks on SuDS/ WSUD globally.
