Sustainable Drainage Systems – achievability over best practice

Sustainable Drainage Systems (SuDS) have long been recognised as a vital part of modern water infrastructure systems but could we show greater leadership by focusing on what is achievable?

Combined kerb drainage which outlets to a swale – an example of achievable SuDS. Image: ACO Water Management.
Combined kerb drainage which outlets to a swale – an example of achievable SuDS. Image: ACO Water Management.

As the leading and pioneering organisation for built environment professionals, ICE rightly helps its members develop best practice in their varied domains. ICE members cannot deliver the benefits of the art and science of engineering for society without delivering the highest quality work. But maybe the pressing need to increase the scale and speed of implementation of SuDS challenges this approach. Maybe now is the time to show leadership through implementing achievable-SuDS?

The importance and benefit of SuDS

SuDS have long been recognised as a vital part of modern water infrastructure systems. The Construction Industry Research and Information Association (CIRIA)'s first edition of the very comprehensive SuDS Manual was published in 2007; the award-winning second edition was published in 2015.

SuDS add additional capacity and flexibility to water drainage systems in cost effective ways. The traditional approach to this issue would be to increase the capacity of surface water systems to cope with very high peaks of runoff – more or larger pipes for instance. However, this is a very expensive solution.

In contrast, SuDS are far more cost effective, providing a variety of ways in which additional run-off management capacity can be provided at the surface or near the surface independently of increasing discharge infrastructure.

SuDS can therefore improve the environment, biodiversity, amenity and quality of a development for its users, providing additional benefits over traditional drainage systems. For instance, a bioswale not only provides infrastructure to trap silt and pollution, it also can add an attractive 'green feature' to a built landscape that adds environmental, biodiversity, aesthetic, social and hence commercial value.

Re-thinking our current approach

Given that SuDS can help manage all types of rainfall and have many benefits, the advantages of SuDS should be gaining far wider acceptance. However, the implementation of SuDS is far slower than had been hoped.

As a result, a number of built environment and water management organisations – the Chartered Institute of Water and Environmental Management CIWEM, ICE and Water UK - are focusing on SuDS implementation in different ways.

In partnership with ACO Water Management, ICE has created a SuDS Task Group to help drive increased implementation of SuDS, focusing in part on 'infrastructure site' level issues faced by built environment practitioners.

Missing easily achievable-SuDS opportunities

One issue that the ICE SuDS Task Group has identified is the inadvertent discouragement provided by emphasising best-practice-SuDS rather than achievable -SuDS. Often, best-practice-SuDS examples are very useful for practitioners new to this issue because they show how SuDS deliver very high quality outcomes for developments, showing multiple features within a single SuDS example. This can help demonstrate many of the underlying principles, which makes initial learning faster for very busy practising professionals.

However, development sites can be complex with constraints. A potential SuDS site adjacent to a road but not near housing or commercial buildings may not need the added value of aesthetic, social and recreational amenity that SuDS can provide although SuDS with such features may add significant value to residential developments.

Even worse, best-practice-SuDS can also help create a misunderstanding of SuDS as complex, high-spec features for luxury developments that are the exception rather than the norm.

In reality, SuDS are highly practical, cost-effective and value-producing approaches to surface water management, so should be understood as inherently achievable and desirable and included in developments as standard practice.

Could achievable-SuDS aid mass roll-out?

A second reason to focus on achievable SuDS is that their earliest inclusion in development proposals optimises the position, layout, effectiveness of SuDS while minimising their cost.

"It can be a battle to make a SuDS drainage solution work around a site layout when drainage features have been indicated without looking at the practicality of where they have been located. Early involvement of the drainage engineer in the design process is key," says Kay Elvy, member of ICE's SuDS Task Group.

Focusing on achievable SuDS and facilitating their future adoption would help all built environment professionals ensure that SuDS are included in the earliest stages of development proposals. This would create a virtuous circle of SuDS implementation. The more planners, developers and built environment professionals see the benefits of achievable SuDS, the more they will be implemented, and the more achievable they will become.

So maybe part of what built environment professionals really need now is enthusiastic support for the design, implementation, adoption, and management of achievable SuDS.