New national standards for sustainable drainage: The right words but missing a mandate

19 June 2025

The Government has published new detailed design standards for sustainable drainage, but it has fallen short on giving them the mandate that would realise their many benefits, writes Alastair Chisholm

Newly published National Standards for Sustainable Drainage Systems are a welcome – and considerable – improvement on the preceding ones.

Sustainable drainage systems (or SuDS, as technical and policy nerds call them) have been known as a crucial way of building climate resilience into our built environments new and old for decades. As climate change has progressed, their value (and, admittedly, their limitations) have become more widely recognised. To the point where, to the initiated, they’re a no-brainer.

Because in a world where surface water flood risk (from intense downpours) is the biggest, and fastest growing kind of flood risk, they soak up water close to where it falls, like a sponge.

Because in a world where heatwaves are a growing problem they can (if planted with appropriate vegetation) reduce the elevated heat stored and emitted by hard surfaces like concrete and tarmac, helping reduce the overall ‘urban heat island effect’.

Because in a world (yes, it’s not just the UK) where combined sewers are getting overloaded they are great at keeping rainwater (the thing that generally does the overloading) out of networks. Reducing the frequency of storm overflow discharges to the environment.

Because, when understanding that our roads are a huge source of microplastics and carcinogenic toxins that flow, generally untreated, into often small streams and rivers and poisoning them, SuDS can filter and start to treat this mucky run-off.

Because (yes, there’s more!) with nature in freefall in what is already one of the most nature-depleted countries on Earth, they can help support increased pollinator, invertebrate, amphibian and plant species populations. And better wellbeing amongst their local human populations too.

Design to deliver

They only do all these things in combination if they’re well-designed.

This has been known for many years and detailed design standards were created under Schedule 3 of 2010 flood management law only to be reduced to two pages (yes, two – plus a front and back cover) in 2015.

Ten years of infuriating drift ensued. During this time SuDS’ potential was wasted, and the opportunity to mainstream them so they became not ‘sustainable drainage’ to developers, planners and others, but just ‘drainage’ – pure and simple – was lost.

Don’t get me wrong, SuDS are delivered in new developments. But they’re often shoehorned into sites after they’re laid out (they’re most effective and efficient if they’re mapped out first, harnessing natural drainage flows across a site so water is a forethought not an afterthought). They’re often ‘value engineered’ to deliver the minimum (two pages) technical requirements. In other words, too often they’re duds, not SuDS.

The new standards go a long way to resurrecting what was developed around 2010 under the last Labour government. For that, we must be grateful. To some they may miss fine detail but to their intended audience – developers, drainage engineers, planners and bodies such as water companies and the Environment Agency, they clearly set out design and performance characteristics to unlock SuDS’ multifunctional armoury.

They cover requirements relating to their ability to manage everyday rainfall drainage and storage, flood risk, water quality, amenity and biodiversity alongside other considerations including their long-term maintenance and where they ultimately drain to. In other words, the specifications necessary to unlock the drainage equivalent of a Swiss army knife.

Delivery still not guaranteed

What has always been a blocker to good SuDS is the mechanism that has been used to ensure they’re actually delivered, adopted and maintained.

The statutory approach to this mechanism set out by Schedule 3 was regarded and lobbied as too rigid and prescriptive. Developer lobbying killed it in 2014.

A government review in 2022 decided various escalating pressures now demanded a mandatory approach was the only way to get builders to deliver necessary levels of performance. This government seems unable to reconcile its housing delivery red tape-trimming ambitions with this, despite supporting it in opposition.

It has to be said that Schedule 3 is not universally loved as a prospect for local authorities, and the experience of its implementation in Wales provided a long list of lessons. There’s no doubt change will need some adjustment within the developer community and capacity building in local authorities, with an appropriate glide path in. But Schedule 3 is robust.

Though it has not formally killed Schedule 3 off, government appears keen to use the National Planning Policy Framework (NPPF) as the driver if possible. The NPPF does prescribe multifunctional SuDS, after all.

However there is a big problem with this approach. It’s that the NPPF is not mandatory. It is guidance and its terminology hangs SuDS in the context of “should” not “must” or “shall”.

This is a crucial distinction, meaning whether or not SuDS are appropriate, or technically fit for purpose in a development is a matter of judgment for planners (who with the best will in the World, aren’t drainage engineers). Open to interpretation, local planning authority to local planning authority, and open to argument by developers.

Given the aforementioned developer position, this has spawned an adversarial climate between planners, lead local flood authorities (who have the drainage expertise) and developers over what gets taken forward.

Planning conditions requiring good drainage because of surface water flood risk are commonly challenged and appealed by developers. Possibly defended by cash-strapped authorities (but often not, given how broke many are) wasting time, public money, and ultimately resulting in new developments with high flood risk. Aspirations over some of the wider benefits are for the birds, under these circumstances.

Ultimately this yields no benefit to anyone apart from lawyers and developers’ bottom lines. It doesn’t even help government’s housing ambitions to deliver more, faster given the potential for dispute and delay. Unless this reality is resolved, the new standards will be largely cosmetic.

And then there’s the question of adoption and maintenance. NPPF guidance recommends having “maintenance arrangements in place to ensure an acceptable standard of operation for the lifetime of the development.” But this happens rarely, it seems.

The new standards refer to single property SuDS being the responsibility of the owner. For multiple-property SuDS schemes, an “appropriate authority” should adopt and maintain them. But the standards don’t prescribe who the authority might be.

Rules-based but light touch?

A rules-based approach seems necessary to ensure clarity and consistency. To remove that local variation in planning guidance and interpretation (which will be helpful for developers). To give the new standards the mandate they need to translate design into outcome delivery. And to give clarity over who’s best to be the adopting (and therefore approving) authority.

The choice on mechanism at the moment seems binary, between Schedule 3 or planning-led. Could there be a third way? We believe there could be. One which mirrors or utilises existing infrastructure approval, adoption and maintenance arrangements in areas such as highways and water company charging, so it’s innately familiar to developers from the get-go.

This could unlock the same multifunctional outcomes from SuDS, as well as a clear route for approval, adoption and maintenance as Schedule 3 would, but in a more streamlined way. There would be rules similar to Schedule 3. But then, there are now too with the new standards.

But rather than setting up an entirely new approving body, local authority highway and land drainage responsibilities (along with those relating to management of the public realm) could be consolidated at the upper tier or Unitary level for the purposes of SuDS management. And nesting adoption within local authorities makes total sense from this perspective as it keeps it close to local planning authorities (as the 2022 government review observed).

As far as paying for maintenance goes, there is already a surface water drainage charge included in water bills. If drainage becomes SuDS-first, then logic states that this established charge is the obvious source for maintenance funding. With minor legislative tweaks if necessary, this money could be passed across to the local authorities to support SuDS maintenance.

One thing is clear: The planning approach hasn’t worked. And new standards or not, it won’t remove that ambiguity and scope for challenge which just seems to be catnip for less-invested developers. It will remain a battlefield and a mess all the while climate change and sewage infrastructure pressure will advance.

We’re pleased government has listened to a wide range of stakeholders in developing these standards. We look forward to supporting it as the rest of the necessary jigsaw is completed.

• You can read the new National Standards for Sustainable Drainage Systems here.

Alastair Chisholm also contributed to the 'Managing rainwater where it falls: EWSC response to the Independent Water Commission', produced by the Enabling Water Smart Communities (EWSC) project.

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Alastair Chisholm is director of policy at CIWEM