Exploring solutions for stormwater management


  • Sue Illman, Illman Young 
  • Chris Carr, FMB national president
  • Steve Wilson, Environmental Protection Group
  • Matt Clutton, Cameron Homes
  • Martin Shaw, Meadfleet
  • Ruth Clarke, Innovyze (sponsors)
  • Jamie Gledhill, Brett Landscaping (sponsors)
  • Charlotte Markey, Polypipe Civils and Green Urbanisation (sponsors)

Our second round table event, held in London in October, saw housebuilders, landscape architects, engineers and product suppliers come together to discuss the imminent legal requirement for sustainable drainage in developments, and bust some myths in the process.

Our second Building Insights LIVE round table event, held at the Building Centre in London, focused on solutions for the soon-to-be-statutory requirement to provide sustainable management of stormwater on projects, essentially by making them permeable. The key goal is to mitigate the effects of development on drainage as we experience more and more extreme weather due to climate change, but also to ensure that the water running off those sites is better quality. However, a further major benefit is the potential for greening our future housing developments using natural features, and thereby creating new standards of amenity for residents.

The round table, sponsored by Innovyze, Brett Landscaping and Polypipe Civils and Green Infrastructure, was a unique opportunity for specifiers to exchange views on how to deliver SuDS (Sustainable Urban Drainage Systems) with key suppliers in an informal setting. It produced a range of constructive pointers, as well as a set of recommendations for the industry (captured at the end of this report).

SuDS is the principal, and established method for achieving such schemes, and there are a range of approaches to achieving it. However, time is of the essence, as with Schedule 3 of the Flood and Water Management Act 2010 about to finally be implemented, housebuilders and developers are confronting a legally binding SuDS requirement in all projects. While they buy into the concepts and the solutions (whether natural, or engineered, or most likely a combination), the practicalities of doing SuDS on many sites are going to be tricky for many.

That’s why our round table event was so timely; as well as bringing together SuDS experts, housebuilders, and product suppliers to exchange ideas and real-life knowledge from practice on the ground, it was also staged just before the new legal requirement came in. Some of the highlights presented here and on our websites (including a new site collating all of our industry insight at insights.netmagmedia.co.uk/round-tables) are certain to be useful to housebuilders as they solve practical issues from how to combine SuDS with public space, to how steep is safe, when it comes to natural features like swales within schemes.

The changes that can be brought about in developments via stormwater management using thoughtful SuDS approaches is an exciting evolution of how future housing developments could look. Far from the tarmac and car-dominated sprawl of the past, driven by the practical need to deal with stormwater but also aiding biodiversity goals, SuDS can lead to natural features in the heart of developments that ultimately provide a level of unprecedented ‘greening.’ While there are major challenges, as explored by our round table, there are also many reasons to be enthusiastic in pursuing these new approaches. 

We were fortunate to be joined by a highly engaged group of people to discuss this important but specialist area – landscape architect Sue Illman is well known in the industry as a SuDS champion, and for engaging with construction sectors in her role as the Construction Industry Council’s Champion for Flood Mitigation and Resilience. She was also co-author of CIRIA’s SuDS Manual which is regarded as the ‘bible’ for designing such schemes. The Environmental Protection Group (EPG) is a firm of ‘geo-environmental’ engineers, and its technical director, Steve Wilson, is, like Sue, a long-standing purveyor of practical SuDS solutions in a host of developments; they both train construction industry professionals including housebuilders on SuDS design. 

From the housebuilder side, we were delighted to have Chris Carr return from our previous round table on Part L; in the meantime he had been elevated to FMB National President! He was forthright in advocating for SME builders grappling with several acute business challenges currently, of which SuDS is just one. Our other housebuilder in attendance was Matt Clutton from Cameron Homes, a medium-sized firm building quality developments across the Midlands and north; Matt combines engineering expertise with a housebuilder’s business outlook, and so offered crucial insights.

Martin Shaw is senior operations manager from Meadfleet, an open space management firm which acts as ‘landscape partner’ for housebuilders across the UK. He views SuDS from
the operational side and helps residents engage with and understand what are potentially unfamiliar features in their developments.

From our sponsors we were pleased to welcome Ruth Clarke, innovation manager at Innovyze, which provides design modelling software to engineers and consultants working on SuDS schemes. Jamie Gledhill, technical engineering manager from Brett Landscaping advocates strongly for permeable paving, and Charlotte Markey, green urbanisation innovation manager at Polypipe, donated her expertise as PhD researcher and promoted a wide-ranging ‘systems’ approach.


The Government’s ‘Plan for Water’ has a stated aim to see “nature-based solutions used, where appropriate.” But what are the best SuDS strategies for housebuilders to take, in order to create the most appropriate schemes in each setting? Collaboration between architects, landscape architects, engineers, housebuilders and planning authorities is the key, but is achieving this an obstacle in itself? 

The round table focused on the general objectives and benefits of SuDS, but quickly saw delegates delving into some of the obstacles (some of which may be imaginary!) for achieving holistic schemes. The attendees began by looking at the Four Pillars of SuDS, CIRIA’s core benefits as well as the must-haves for installations to be deemed a success. Firstly, water quantity – tackling stormwater via slowing its progress as close to the source as possible, rather than removing water quickly from site using pipes. As SuDS expert, landscape architect Sue Illman told the group, “the whole point about SuDS is to have a multiplicity of features, and that each one, particularly where they’re on the surface and involve planting, slows that flow because the water will be intercepted as soon as it hits the ground.” 

The second pillar is water quality – natural SuDS can in themselves clean the water coming off a site. “For example,” Sue explained, “a swale is a wet-dry system, the water goes through it, then it dries out, and this process metabolises the hydrocarbons from roads.” This is augmented by planted systems whose roots help to control silts and sediments, further cleaning the water supply. Those chemicals which cannot be filtered by planting remain trapped in the soil, rather than entering groundwater reserves.

The final two pillars are Amenity and Biodiversity – two inter-related benefits of SuDS, firstly the ability of SuDS to provide a whole new public area within developments for residents to see, and use. Nature-based SuDS schemes are a proven way to produce species biodiversity on sites, and thereby help meet the January 2024 requirement for a 10% uplift in Biodiversity Net Gain. 


We asked all of our attendees to provide a question or comment for the group to tackle. Steve Wilson of EPG suggested that how SuDS contributes to biodiversity was a key issue to assess. Martin Shaw from Meadfleet made the case for including SuDS as not just a functional necessity, but as an amenity in housebuilding schemes, and how features such as swales, filter strips and of course trees add value to residents’ lives. 

He told the delegates: “As the SuDS systems mature, the visual amenity is far greater than having a concrete basin or channel; we get our ecologists involved to improve the site’s biodiversity, in one example in Epping we have linked a balancing pond with a woodland, with native trees planted around it.” He continues: “It’s matured into a lovely place where families spend a day out. SuDS can become a massively valuable part of the development.” Martin added that wetland margins around such a feature further slow the water, soaking into the ground rather than running straight into the pond. 

Developments can look different to what has traditionally been expected by residents, with longer, wilder grasses which can suggest a lack of maintenance, and lead to a stigma against them. Delegates asserted that education was essential to combat pushback against schemes which is driven by lack of knowledge. Martin from Meadfleet said that getting maintenance right is also key to helping residents become more accepting of these new features – he said that regular planting, such as poppies in one recent Meadfleet case study, “shows people that the area is being looked after.”

Steve Wilson of EPG said that “from international experience, wherever there have been large-scale SuDS schemes are successful is where there have been massive public awareness campaigns so people are educated about them,” and warned that currently in the UK this was “non-existent,” so education is in severe need of improvement. “The Government really need to get to grips with it and make people aware of why it’s there.”

Is SuDS genuinely a ‘win win’ for small developers and their customers, and could the Four Pillars be potentially easier to achieve on some smaller semi-rural schemes, than their more space-compromised urban counterparts?). Perhaps more importantly, who is driving SuDS adoption in residential schemes, are customers so unaware of the benefits that developers have to sell it to them, whether or not there’s any commercial advantages for the housebuilder per se?

Chris Carr posed the question as to whether developers should include SuDS as part of marketing to customers, given that his firm “embraces it as a positive.” Sue Illman gave the view that it should be included in the booklets which housebuilders tend to provide their customers when they get the keys, explaining features of their new home. 

Chris responded that while “education could sometimes be seen as lecturing, in this case it’s really positive,” due to the host of benefits that SuDS can bring developments. He added: “We have to have a USP as a small builder against the volume housebuilders, but it needs to be”layered with things like open space, biodiversity and the Future Homes Standard, it can’t be just an engineer designing for SuDS.” 

Charlotte Markey questioned whether homeowners were “pushing from the bottom up to get SuDS implemented; there are loads of case studies of beautiful schemes, but have people aesthetically got used to such a poor baseline that they’re not actually demanding it from housebuilders?” Chris Carr commented: “We have to sell it to them,” and Matt Clutton from Cameron Homes agreed that there is a long way to go with consumer buy-in, given that “a lot of people are moving towards astroturf for gardens.”


When it came to how the volume housebuilders were approaching SuDS, Steve Wilson recounted to the group his experience of being called in to train volume housebuilders’ planning and buying teams on SuDS design, as “they recognised the commercial advantage, and that it would be a lot cheaper if you get it right from the start.” He added: “They also recognised that land take isn’t an issue if you design it right, conversely, if you put appalling SuDS in that are ‘bomb craters,’ it is going to take a lot more land, and probably cost more to build, and people aren’t going to like it.”

What are the key issues for housebuilders in complying with SuDS in the current context? Procurement is riven with problems, and some planning authorities may be more amenable than others when it comes to creating comprehensive SuDS schemes as part of new developments. Our panel discussed the issues around the hierarchy of decision-making in projects, and the organisational and bureaucratic obstacles that overcomplicate things.

Steve Wilson of EPG told the group there were “a lot of artificial organisational boundaries that make SuDS difficult – technically it’s straightforward,” adding: “What we really need is a wholesale rewriting of surface water legislation.” Jamie Gledhill of Brett Landscaping pointed out that a major nut to crack in the procurement process was Highways departments, who “do tend to be the main blockers” when it comes specifying SuDS projects.

Chris Carr admitted there were issues with SuDS features in highways, although it may seem like one of the best locations to introduce them. For example, swales are seen as incompatible with highways services connections such as street lighting, meaning that two rows of streetlights may not be possible. However he said that this is feasible “because of the issue with energy costs now, local authorities are happy to reduce street lighting.” He admitted that while some maintenance was straightforward, such as ponds, when it came to long stretches of swales for example next to highways, this was much more challenging. “We might have two or three thousand metres of swale,” Carr commented. 

Is it a myth that SuDS costs more than a traditionally landscaped and road network-oriented scheme? A 2013 Defra study even found that well-designed, landscape-based SuDS should be cheaper than traditional drainage with underground storage, with less pipework. Ruth Clarke from Innovyze asked whether housebuilders “were able to charge more for properties based on the increased amenity, or are SuDS still just seen as a necessity to get planning?”

Land take is the key issue in terms of affordability, as developers have to sacrifice land they could build on to include SuDS, but in theory their developments are more desirable as a result, so there’s a balance. But, as Matt Clutton of Cameron Homes pointed out, there’s a key problem which planners bring into the picture, by “requiring a certain amount of public space in schemes, but not including the SuDS feature in that area.” Therefore, SuDS places a further burden on the land equation, when it could be integrated into the calculation of public space. Steve Wilson agreed it was “a real problem, it makes SuDS expensive – we’ve got to look at multi-functional use of open space.” 


Sue Illman posed the key question of how to ensure all the professional disciplines “fully understand SuDS and the multiplicity of ways that they can be designed into projects.” While this might not have been answered, there was consensus that collaboration between architects, engineers and other professions was possibly more essential for these schemes than others. Chris Carr candidly admitted that for his firm, “there is a hierarchy, and landscaping comes at the bottom, they have to deliver the best they can with the engineered design, SuDS, highways and everything else; you can’t lead with landscaping, it would never work.” 

He advised: “When the engineer’s finished, then look at how to incorporate landscaping into it.” He added that “my first priority as a developer is to build a home I can sell, and everything else has to work around that.” However, Sue Illman and Charlotte Markey defended the importance of prioritising landscape architecture in the process, Sue asserting in response to Chris: “We do it the other way around,” questioning why engineering would be given the chief priority. Charlotte adding that it was “hugely frightening that you can’t have a landscape-led approach.” She warned that “we are getting used to such a terrible baseline in this country where infrastructure just becomes dominant.” 

Charlotte cited how Polypipe’s Civils and Green Urbanisation division is working with EPG, as one example of collaboration, “because we want to encourage a wider raft of solutions.” She added that “Hopefully with Schedule 3 being implemented, green solutions will be adoptable, but that doesn’t mean you have to take a purist perspective.” She admitted that using plastic underground for the engineered element of a project “was a legitimate concern,” but that greater awareness was needed of the fact that “a lot of companies now don’t use virgin plastics, or are looking at alternative solutions.” She added: “In some instances there might be a necessity to combine approaches when you have a lack of space.” 

Steve Wilson of EPG continued the theme, counselling housebuilders: “Your aim starting out should be for a fully natural system on the surface, but the constraints you come across will push you to put some plastic structures in there.” He also described how the Environment Agency had precipitated an exponential rise in requirements for storage on projects to account for future climate change-driven flooding, which has climbed to 40%, “a massive amount of storage, and that can make it unviable.” However, Charlotte Markey added that “there could be so many instances where shallow tree pit solutions and rain gardens with playscapes could be incorporated to reduce the land take, because people want more for less now.” 


Our delegates discussed some of the perceived myths, and received wisdom around SuDS engineering, such as the so-called 5 metre setback rule in SuDS schemes. This states (inherited from old guidance, that no SuDS feature can be placed closer than 5 metres from any building, however Steve Wilson for one was here to debunk this myth: “It’s not going to affect the foundations; a lot of them these days are piled, and it’s not going to make an iota of difference.”

One comment was submitted by Dick Longdin, of Randall Thorp landscape architects (who was unable to attend the event): “There’s often a lack of creative input from landscape architects at the initial design stage which can result in very engineered solutions, such as 1:3 slopes.” The round table discussed whether overly engineer-led solutions could mean that simple ‘pipe to pond’ approaches can lead to a ‘pipe to a crater at the end of the site.’ 

There was general consensus that SuDS can be much simpler to get right than many believe, given early collaboration between landscape experts and engineers on schemes. Alternatively if left to engineers, the result can be steep-sided SuDS features schemes which work practically but present an eyesore and even a danger for residents. As delegate Matt Clutton from Cameron Homes phrased it in his question to the group, when designing swales for example, “how steep is too steep?” 

Sue Illman offered some insight from experience: “1:3 is steeper than you think when you actually see it on the ground.” Steve Wilson added: “I think you should keep it as shallow as possible, then you can steepen it up if needed, but when you stand at the bottom of something that’s 2.5 metres deep and look at a 1:3 slope it’s really steep, it’s horrendous.” He continued: “So, the deeper you go, the shallower the sides’ slopes need to be, which is an incentive to keep the depth shallow.” 

Matt Clutton offered the developer’s perspective: “It needs a lot of input and collaboration, the ground might be sloping, and one side of the pond might be 2 metres higher than the other, so you need the engineers to model it, and then introduce the landscape architects.”


The Government appears to be sticking to 300,000 homes per year as an ‘aspiration,’ at least, and Labour is pledging to build 1.5 million homes. The pressure is on for new developments across the UK, and on developers, to design sustainable drainage solutions that reduce the impact of those developments on their local area and beyond.

The case for SuDS is clear, they deal with stormwater, clean our water supplies and mitigate the impact of our developments in urban sites. They can also, space permitting, help meet Biodiversity Net Gain requirements and greatly enhance projects for residents. Bringing in the full range of possible solutions (for the full benefits) may be a challenge for many, such as SMEs, as the SuDS becomes mandatory in 2024. However, our round table and its recommendations (below) help support the argument for diving fully into the potential to use SuDS to green developments for everyone’s benefit, caveated with key practical suggestions.

Our event also highlighted some remaining gaps in knowledge, including between SuDS aficionados, and housebuilders tackling a raft of difficult problems. However, we think that the event was one valuable effort in the battle to plug those gaps. We didn’t have time to delve further into issues like whether permeable paving should be considered as a ‘natural’ SuDS solution, and the quirks of water companies demanding certain unnecessary engineering solutions causing more complexity than is needed, but we hope to return to this key issue for the industry in future events.

We would like to thank our sponsors, Innovyze, Brett Landscaping and Polypipe Civils and Green Urbanisation for supporting Building Insights LIVE.


Sue Illman, Illman Young landscape architects – I want to make a plea for using wetlands – they are incredibly diverse and people don’t use them enough. People should use them much much more because they fit your Biodiversity Net Gain, along with your SuDS and attractive landscapes and lots of other things, so you get big bang for your buck.

Chris Carr, Federation of Master Builders – At the moment we are trying to appease everybody, whether it’s the Highways department, water company or anybody else – just have one policy that covers it all, from rain to sea. There’s too much conflict between external bodies, you’ve got to be a bit more holistic. 

Steve Wilson, Environmental Protection Group – We need proper multi-disciplinary design, where it’s a partnership, not one discipline being more important than another. 

Matt Clutton, Cameron Homes – Education of both customers and planners, where they are segregating out the area that’s public open space from the SuDS – they need to be combined, which will help with the education because residents will be going into the feature to use it, and will see the benefits.  

Martin Shaw, Meadfleet – The main thing to consider when designing and developing these systems is the lifetime management of them, because they’re a legacy for everyone. 

Ruth Clarke, Innovyze – Everyone being involved at the right time in a project – everyone is involved, but whether that gets fed in at the right time, and the bigger picture needs to be looked at – and the adoption by any water company is really key.

Jamie Gledhill, Brett Landscaping – Multifunctional design, and incorporating engineering with landscape design – stop calling it ‘engineering SuDS,’ it’s ‘designing SuDS.’ Like Clive Woodward’s approach  in England’s rugby world cup win in 2003, it’s ‘every one percent that you can add in,’ whatever you can add in, it’s going to be better in the long term.

Charlotte Markey, Polypipe Civils and Green Urbanisation – It’s about how you manage an entire system, it’s helping people transform their practice through managing those complex systems, but they’re not as difficult as we think. It’s just having that system approach – if you change something early on, it’s going to have a knock-on effect on something else, and we just need to know where we make the changes and how we challenge them.