Sustainable Drainage Systems (SuDS) are an undervalued tool in the battle to deliver cleaner waterways. They reduce water volumes entering combined sewers, cutting the likelihood of sewer overflows and they filter out pollutants, improving the water quality of the receiving water body. They also offer huge potential to support compliance with the Environment Act 2021 that requires water companies to ensure a progressive reduction in the adverse impacts of discharges from storm overflows. So why are they often overlooked?
In a recent webinar, hosted by the New Civil Engineer, in partnership with Wavin, experts explored the future of SuDS in England. In it, they discuss how raising the profile of SuDS, growing the necessary expertise, incorporating SuDS into the planning process and building industry consensus behind this approach to drainage could, and must, transform England’s water pollution experience. In this article we delve deeper into some of the issues covered by the webinar, including direct quotes from the discussion.
Concern about water quality is rising
We’re operating in a water environment that’s overshadowed by storm overflows and sewage discharges. Stark news headlines regularly spark public debate around whether it’s still acceptable to discharge dilute sewage into receiving water bodies.
Thanks to mandatory monitors on storm overflows and the Event Duration Monitoring (EDM) data, we are getting a fuller picture than ever before. In 2021, water companies released untreated sewage in England 372,533 times for a combined total of more than 2.7 million hours across approximately 15,000 storm overflows. And the average number of monitored spills per overflow was 29 in 2021, with 87% of storm overflows having at least one spill in 2021 and 5% spilling more than 100 times – and that’s just for the 89% of overflows that currently have monitors.
This clearly indicates the scale of the issue and how our water infrastructure – particularly components and sections constructed during Victorian times - just can’t cope with a growing population, increased urban density and the pressure of more frequent extreme weather events.
But it somewhat overlooks other polluting factors that affect water quality such as nutrient pollution, where overloads of nitrogen and phosphorus act like fertiliser and cause excessive growth of algae. In reality, tackling this must also be a priority if rivers and lakes are going to continue to support biodiversity and provide safe places for leisure water activities.
There’s deep concern across the water industry about water quality, and significant numbers are looking to regulation for answers.
Professor Richard Ashley, Professor of Urban Water, Sheffield University
The Environment Act doesn’t go far enough
Although there’s support throughout society for action against water pollution, current legislation isn’t as tough as some would like. High expectations were placed on the 2021 Environment Act as a potential catalyst for change, but is it living up to these hopes?
The Act sets out to foster better collaboration between water companies, modernise licencing processes and make management planning for drainage and sewage a statutory duty. It also introduces environmental protections where water changes, such as flooding, can lead to damage.
It seeks to directly improve water quality by tackling the major causes of pollution to UK rivers and, importantly, places a legal duty on water companies to progressively reduce the adverse impacts of discharges from storm overflows. Despite these changes, many experts are frustrated that the Act isn’t more powerful – putting a firm date on the end of overflows, for example - and are wary that its provisions can be side-stepped or mitigated by water companies.
Professor Richard Ashley, Professor of Urban Water, Sheffield University
SuDS aren’t a new solution to improving water quality
Using the natural environment, SuDS have been a viable option for reducing water volumes entering combined sewers and filtering out pollutants for more than quarter of a century.
The basic principle of SuDS is to bring the ‘processing’ as close to the point of water collection as possible, slowing water down, rather than just getting rid of it quickly, allowing water quality improvements. Traditional pipe drainage doesn’t manage pollutants. Instead, it focuses on rapidly moving the contaminated water directly to the receiving water body.
SuDS break this cycle by working to filter water back into the ground, using natural processes that enhance water quality. By keeping runoff water near its source, SuDS allow it to soak through a layer of subsoil before re-joining the water table. Using a variety of mechanisms – soakaways, infiltration trenches and basins, rain gardens and geo-cellular tanks, for example – SuDS facilitate the filtration, adsorption, ion exchange, precipitation and microbial action that clean the water as it moves through the soil.
This reduces the volume going into combined sewers, making overflow discharges less likely and improving the quality of the water joining lakes and open waters.
Martin Lambley, Head of Stormwater Management, Wavin
SuDS and industry structure aren’t aligned
So, if the benefits of SuDS are so clear, why are SuDS not at the heart of every new development and regeneration project?
The experts are unanimous: in England it’s because they’re not mandatory and the structure of the water industry works against the introduction of SuDS.
Water companies are operating within structures that were created at least 30 years ago, and their drivers no longer fit with what government and society are trying to achieve regarding water quality. The key duty of a water company is to deliver profits to its shareholders, and this comes before offering a service that priorities social and environmental good.
On top of that, experts believe there’s no clear, consistent guidance from the regulator. There’s a history of launching five-year plans and 25-year plans that don’t necessarily have the same goals at heart.
The combination of these factors means regulatory guidance lacks direction and water companies are reluctant to take action on SuDS. So, although the technology and the expertise exist, and there’s growing support for SuDS generally, water companies aren’t incentivised to facilitate this change and make SuDS a widespread reality.
Martin Lambley, Head of Stormwater Management, Wavin
There’s no agreed legislative approach to SuDS
Approaches to SuDS implementation across Scotland, Wales and England vary dramatically, demonstrating the divide between England’s focus on addressing flooding, and a wider, water-quality focus in Scotland and Wales.
Scotland’s approach
Scottish legislation makes specific provision for promoting sustainable water use and ensuring the progressive reduction of pollution of groundwater - as well as mitigating the effects of floods. Scotland has long built a SuDS policy into local planning laws, reflecting the prioritisation of protecting water quality rather than flooding.
The Scottish Environment Protection Agency (SEPA) holds responsibility for the protection of the water environment and stipulates that SuDS are built into new developments. SEPA stipulates that, if a developer constructs SuDS to Scottish Water’s standards, Scottish Water has a duty to adopt and become responsible for the SuDS, should the developer request it.
Professor Richard Ashley, Professor of Urban Water, Sheffield University
The Welsh approach
In Wales, there are clear lines of responsibility concerning SuDS and water quality. In 2019, Schedule 3 of the 2010 Flood and Water Management Act came into effect, requiring new developments over 100sq/m to include SuDS that comply with mandatory Welsh national standards. A supervisory SuDS Approving Body (SAB) makes sure developers demonstrate their Schedule 3 compliance in their planning application. It approves designs, monitors installation and supervises adoption by the relevant local authority upon completion.
Effectively, Wales have disconnected water company shareholders from the provision of ecologically sound water services with thorough reform of water companies, the regulatory body Natural Resources Wales and its local authorities. There’s also clear evidence that Wales is applying the same water-quality-first principles to retrofitting SuDS.
Recognising that new developments would place too much strain on the existing public sewage network – even before the adoption of schedule 3 – recent new developments in Wales incorporated SuDS and all parties involved collaborated to determine a long-term adoption strategy. In the Plasdwr development near Cardiff, for example, a management company adopted the SuDS, with the leading local authority becoming a 50% stakeholder in it. Developers will work with the SAB to determine the control of future phases of SuDS development – in line with Schedule 3 - giving peace of mind and clarity about SuDS responsibilities.
Julian Hill, Head of Adoption Services, Dŵr Cymru Welsh Water
The approach in England
England hasn’t adopted Schedule 3, choosing instead to adapt the National Planning Policy Framework. This does stipulate that flood risk is taken into account at all stages of the planning process, and that development avoids areas at the highest risk of flooding. It states that developments should only be allowed in areas of flood risk if they incorporate SuDS, unless there is clear evidence that SuDS would be inappropriate.
The Framework stipulates that SuDS should be incorporated into developments of 10 dwellings or larger (or equivalent non-residential developments), unless demonstrated to be inappropriate by the developer.
This has created a situation where developers, often believing SuDS are more expensive that traditional piping, can object to having to implement SuDS, and frequently succeed in overturning this stipulation.
What’s more, the onus is on the developer to explore adoption and ownership possibilities as there is no single adoption route. And with many water authorities reluctant to adopt SuDS schemes for various reasons, uptake is slow.
Shaping the future of SuDS
To a large extent, SuDS are a hidden part of development and water policy. This is partly because they’re designed to appear as attractive ponds, rills and rain gardens, so the public assumes they’re amenity improvements rather than practical drainage solutions.
However, flooding and water quality are emotive issues, and connecting SuDS schemes directly with this messaging would be extremely effective. Schemes that have taken the trouble to explain their purpose have overwhelmingly received public support, so perhaps it’s time to raise awareness of SuDS? Martin Lambley, Head of Stormwater Management, Wavin
Any education of the public must be matched, or even exceeded, by education within the water community.
At a training level, it’s still possible for an engineer to complete their degree with only a light touch awareness of SuDS. We need to shift the focus from traditional drainage to sustainable drainage techniques, incorporating them throughout the educational journey so we produce a generation of engineers who proactively design and implement SuDS that push the boundaries of what’s possible.
This mindset change will be critical in growing the SuDS expertise England needs if and when it ultimately adopts Schedule 3.
Martin Lambley, Head of Stormwater Management, Wavin
As the history of SuDS shows, without one single body in overall control, policy can be watered down and become less effective.
Greater powers for local authorities would remove the automatic right of developers in England to connect drainage systems to public sewers. Designating the local authority as the SAB would drive SuDS take up in development policy. It could also take away the grey areas that currently exist in English governance that allow water companies to postpone tackling water quality issues.
Supported by a growth in expertise, a SAB that sits within the local authority is an opportunity to create centres of SuDS excellence.
Julian Hill, Head of Adoption Services, Dŵr Cymru Welsh Water
Although SuDS need SABs to act as a single, strong driving body, they also need a collaborative, inclusive approach to make surface water management as effective as possible.
Experts recommend that early engagement of all parties involved in site planning is essential to a smooth project and SuDS adoption, as well as cost-efficiency.
The role of SuDS and the best methodology for implementation have recently been placed firmly back on the agenda with the publication of DEFRA’s 2022 report into ‘Assessment of how strategic surface management informs Sustainable Drainage Systems (SuDS) delivery through the planning system’. It reviewed the effectiveness of current strategic surface water management plans in terms of how well they laid out the requirements for SuDS. This included looking at how strategic surface water management plans could be used more effectively to define local planning authority SuDS requirements.
Martin Lambley, Head of Stormwater Management, Wavin
As society increasingly realises the value of water and the potential impacts of scarcity, it will be important to move to an integrated water management approach.
SuDS are a core part of this, bringing water re-use closer to the point of collection, and shifting thinking from the Victorian pipe-away policy towards greater water recirculation. For example, every new home could have integrated rain butts that channel water to flush toilets, rather drawing from the fresh supply.
Professor Richard Ashley, Professor of Urban Water, Sheffield University
Making water an opportunity
Experts agree that making water an opportunity, rather than a problem, is the key to effective water management. However, this will take concerted action from all sides of the water industry.
There are clear lessons to be learnt from the Scottish, Welsh and English routes to water regulation and a sense that the industry needs to move on from this exploratory phase by making change now.
SuDS are an established, proven method of addressing water quality issues. They have the power to protect existing infrastructure from being overwhelmed and they limit water pollution in the process. By harnessing natural ecological processes, they’re also ready to improve water quality close to where the water originates.
There is definitely work to do. As Professor Richard Ashley says, “We still need to move into a stronger water sensitive perspective… we need to look at water in an entirely different way and, at the same time, completely reform our institutional regulatory system.”
To find out more about what the experts had to say, including a discussion about the circular economy of water, take a look at the New Civil Engineer’s webinar in partnership with Wavin.
