Why it’s time for a SuDS rethink to meet new Schedule 3 requirements

Significant change is coming to the new build market: during 2024, incorporating sustainable drainage systems (SuDS) into most new developments in England will be required by law.

New legislation will remove a new development’s automatic legal right to connect surface water drainage to nearby sewage infrastructure. Instead, England’s newly adopted Schedule 3 of the Flood and Water Management Act 2010 will be implemented, making SuDS a mandatory requirement for developments over 100sq/m.

While many developers were aware this change was coming, some are yet to think through the full implications. It’s important to grasp that SuDS aren’t ‘just’ an extra line on the build plan, they require careful consideration and tailoring to each site. This makes them a shaping factor in the fundamental design of a development, and forward-thinking developers are already investing time to work out the best approach to take in order to maximise the benefits of SuDS for their business.

In this article, we’ll look at how leading developers are approaching the change to mandatory SuDS.

How we understand sustainable drainage systems today

SuDS are all about minimising the effect of the built environment on the natural water cycle, and the fundamental purpose of a SuDS solution is to enable a developed site to handle rainfall and surface water runoff as if it were still a greenfield site. To achieve this, SuDS are designed to mimic natural drainage by managing surface water runoff as close to the source and the surface as possible, rather than overwhelming stormwater drains and risking flooding.

The main SuDS approaches take one of three routes to tackling runoff near to source: enabling runoff to naturally soak into the ground (infiltration), providing opportunities for it to evaporate from surface water (evaporation), or promoting transpiration from vegetation (evapo-transpiration).

By now, most developers in England are aware of these basic aspects of SuDS. However, ‘how’ these SuDS approaches are implemented is a crucial factor that offers huge potential for developers to give their developments competitive standout.

“How developers choose to implement the SuDS schemes required by Schedule 3 will be crucial in future. SuDS are set to become a defining factor in the price developers can achieve for their upcoming new build developments and for how smoothly they can obtain planning permission for future sites. Smart decisions now will pay off in the future.”

Anthony Kolanko, Urban Climate Resilience Commercial Manager, Wavin UK

Smart decisions for implementing SuDS

Historically, in many quarters of development, the go-to SuDS choice has been to use engineered, artificial solutions rather than creating natural landscape features that achieve the same purpose. The dominance of engineered SuDS over landscaped SuDS has been driven by the importance placed on ease of installation and keeping costs as low as possible.

Engineered SuDS, such as permeable paving or geocellular attenuation and infiltration tanks, are proven solutions that are easy to fit and give great value for money. They can store a large volume of water in a relatively small space, and it’s possible to predictably design capacity and flow rates, meaning engineers can easily and effectively model situations for different sites. They also don’t divert as much land from housing, allowing a higher density of building than is typically possible with landscaped SuDS. Plus, engineered SuDS are repeatable, with proven capabilities that reassure planners about how the site will cope with water runoff.

For many developers up until now, these easy to install, proven and affordable solutions have been the end of the matter, and they’ve maximised the use of engineered SuDS in their developments. But, as opinions and expectations of new developments evolve, a purely engineered SuDS approach looks increasingly short-sighted.

“Engineered SuDS, particularly geocellular attenuation tanks, underpin effective water runoff management. They’re easy to design and install, and they work well every time. But there are other factors involved now and, as an industry, we need to look again at how we implement SuDS to create the spaces people want to live and work in.” Anthony Kolanko, Urban Climate Resilience Commercial Manager, Wavin UK

Despite their obvious benefits, it’s critically important to recognise that engineered SuDS are only designed to manage the quantity of water runoff. They do this extremely efficiently and there will always be a place for permeable paving and geocellular attenuation and infiltration tanks in construction. However, they only meet one of the four core criteria for an ideal SuDS solution. Ideally, a SuDS scheme will go beyond managing the quantity of water runoff, and will reflect the ‘four pillars’ of SuDS that also include managing water quality, adding amenity to a site and creating a habitat for biodiversity.

In contrast, landscaped SuDS manage runoff volumes and more, meeting extra functional requirements (such as improving water quality) as well as addressing wider issues such as promoting health and wellbeing or enhancing the environment. They also take many forms, so developers can mix ‘n’ match solutions to best fit the site in question. Green roofs, rain gardens, tree pits, swales, infiltration basins, soakaways and constructed wetlands are just the beginning. Rather than being hidden underground, landscaped SuDS become features within the development, enhancing the space in ways that improve residents’ quality of life, benefiting the environment, and improving water quality.

Historically, developers have automatically considered landscaped SuDS to be more complex to implement, and potentially more costly, since they can require land that would otherwise be used as building plots. But with Schedule 3’s implementation heralding a new era of SuDS in England, leading developers are looking again at what SuDS can bring to their business. They’re also aware that future regulation may go wider than the 2024 specifications, requiring SuDS schemes that do more than manage water runoff.

As a result, they’re going back to first principles and using the four pillars of SuDS to guide their SuDS strategy. This involves considering how a careful balance of engineered and landscaped approaches can create more liveable spaces, appealing to buyers and potentially offering the most future-proofed direction.

In brief, here’s what developers need to know about the theory behind SuDS, and how reflecting this in new build developments can benefit their business.

The four pillars - the holistic purposes of SuDS

The over-arching theory behind SuDS is best summarised by the ‘four pillars’, as defined by the Construction Industry Research and Information Association (CIRIA), a neutral, independent and not-for-profit organisation. The CIRIA SuDS Manual is the key reference document for all the interdisciplinary experts and trades involved in the development of new homes.

For a while now, Welsh building standards have specified prioritising the four pillars in every SuDS system, and developers operating in Wales also find the CIRIA Benefits for SuDS tool and the RSPB/WWT guidance on designing SuDS for people and wildlife useful resources for guidance.

The fundamental point to take away here is that any robust SuDS programme will think widely and always reflect the four pillars of SuDS:

Pillar one - managing water quantity

This reflects the essential requirement to tackle runoff scenarios that could overwhelm storm drains and lead to flooding, so it focuses on using attenuation to manage the volume and flow rate of surface water runoff to that of an equivalent greenfield site. It aims to restrict the flow of surface water and to slow its movement to the next stage of the system.

Pillar two - managing water quality

Surface water comes into contact with a variety of pollutants, particularly from roads and the vehicles that run on them. SuDS work to remove pollution from the natural environment and to improve the quality of water entering combined sewers.

Pillar three - creating amenity

An effective SuDS project is about place-making and the human desire for a green environment. This pillar is about improving the quality, character or overall enjoyment of an area. This could include, for example, providing green places within an urban environment, improving the air quality, or enhancing a streetscape.

Pillar four - creating a habitat for biodiversity

Increasing urbanisation has disrupted natural wildlife habitats and ecosystems. SuDS can seek to replicate what would have existed in a greenfield site, benefiting water quality and urban wildlife, and reflecting the growing awareness of environmental responsibility amongst the general population.

Why the four pillars of SuDS are important right now

Each of the four pillars represent areas of significant value to the general public, and have the power to influence decision-making over where to buy a property.

Pillar one - managing water quantity

As the climate changes, and intense rainfall events become more frequent, the risk of localised flooding increases – and this has registered in the public consciousness after widespread media coverage. People now understand that areas previously considered safe from flooding may now be affected by it. They’re also aware that developments over the last decade have encroached on flood plains, bringing enhanced risk.

The result? Buyers want reassurance that their new home will be protected from flooding.

Pillar two - managing water quality

Water quality has risen up the public agenda, too. There’s been outrage over water company profits while sewage spills and overflows continue to rise. Off the back of increased media coverage, water companies in England have apologised and pledged to invest £10bn this decade in infrastructure improvements.

The result? Buyers want evidence of local action to protect water quality.

Pillar three - creating amenity

The pandemic experience made nearly two-thirds of people realise how much they value quality green spaces, meaning they want them to be a higher priority for the government. However, an increase in high-density living has led to a loss of greenspace: neighbourhoods dominated by the most recent generation of housebuilding have up to 40% less green space provision than older neighbourhoods. People also increasingly understand that ‘greening’ neighbourhoods brings a host of wider benefits such as improving air quality, reducing summer temperatures and making cycling and walking more attractive travel options.

The result? Buyers prefer developments that include green spaces and will potentially pay more for them.

Pillar four - creating a habitat for biodiversity

Awareness of the importance of biodiversity is growing as the implications of climate change sink in. In 2021, 75% of adults in Great Britain said they were worried about the impact of climate change. Those numbers, and the intensity of people’s concerns, are set to rise.

The result? Buyers want to live in environments that are more sustainable and make space for the natural world as well as for humans.

Plus, encouraging biodiversity is going to become more important to developers in the near future as planners specify a requirement for Biodiversity Net Gain (BNG) within developments, with the purpose of leaving the natural environment in a measurably better state than it was before building began.

What does this mean for the developer’s approach to SuDS?

From now on, every site will need a carefully thought-out SuDS approach that balances the benefits and limitations of both engineered and landscaped solutions.

Delivering SuDS will become a collaborative discipline, bringing together engineers, landscape architects, business planners and site managers to consider the options and maximise the benefits for each site. Topography and the size of a site, as well as the infiltration potential of the underlying geology, will all come into play and creative SuDS solutions should be utilised where more straightforward options aren’t appropriate.

“SuDS today are about smart thinking, incorporating landscaped schemes on site areas that are less suitable for building and backing them up with highly reliable engineered systems – usually geocellular attenuation tanks. This powerful combination optimises resilience against climate change and extreme weather events, while at the same time creating an environment that’s good for people, good for nature and can command a high sale price. A little creativity at the design stage can go a long way, for example, where space is tight, why not explore how you can get dual use out of a plot? Attenuation tanks under a playground, for example, deliver a valuable placemaking benefit, while also managing surface water run-off.”Martin Lambley, Urban Climate Resilience Global Product Manager, Wavin

How Wavin solutions underpin this new SuDS approach

Our role in this new SuDS era is to deliver the ultra-reliable, cost-effective geocellular attenuation tanks that will continue to be at the frontline of water runoff management.

Geocellular construction is the leading form of building attenuation tanks because they’re modular (with a honeycomb structure) and so can fit into small spaces, offering flexibility over length, width and depth. They’re extremely space efficient, with a typical surface water holding capacity of 95% or above, and strong enough to sit relatively close to ground level. There’s also a wide range of choice to suit traffic-bearing and non-traffic-bearing areas. And they’ve been specifically designed to be quick and easy to install. Our Wavin range also features hand grips to make them easy to carry, as well as integrated, push-fit connectors that click into place without pegs, clips or tools in half the time it takes to install comparable units.

Start planning your Schedule 3 strategy today

Now is the perfect time to investigate the potential benefits of a combined engineered and landscaped SuDS approach, so you’re ready to exceed your obligations under Schedule 3.

We have a wealth of experience integrating our market-leading geocellular attenuation tanks into a landscaped SuDS concept – reinforcing a site’s ability to cope with water runoff. You can find out more about our attenuation solutions here, or get in touch to talk through your options.

​Want to find out more about Urban Climate Resilience at Wavin? please get in touch below.