10Oct 2013

SuDS, WSUD and Blue/Green Infrastructure – what’s the difference?

Alex Stephenson, Hydro International


Across the globe approaches to sustainable water management are getting more sophisticated as we recognise just how closely intertwined our lives are with the water cycle.


Historically, we separated out the way we think about water: waste water; drinking water; stormwater; rivers and coastal waters – we have compartmentalised, industrialised and managed each separately.


Now, climate change and more responsible environmental stewardship are driving us to realise that our approaches to water should be much more interconnected – and that integrated urban water management can have highly positive social consequences.


It’s an evolution that’s happening the world over, although countries are developing their legislative frameworks to water management in different ways, depending on the priorities of climate, water scarcity, flooding and population growth.


As the world becomes smaller, our ability to share and adopt best practice is rapidly accelerating. New water management approaches evolve in different places then ‘cross-fertilise’ by recognising similarities and sharing new ideas. You only have to look at the Australian winning garden at this year’s Chelsea Flower Show to see it in a nutshell: the refreshing message was for UK householders to disconnect their downpipes and build billabongs in their back yards!


So, when Paul Shaffer tweeted the question: what exactly are the differences between SuDS, WSUD and green/blue infrastructure – and what is just smoke and mirrors? – I stopped to think.


WSUD image crop (500x499)



My problem is that I strongly believe terminology can – and in some cases has – become the enemy of really good water management. Such terms are open to interpretation – or misinterpretation – and to being adopted for differing agendas. 


Of course, we need to have terms to ‘hang our hats’ on. So I will attempt my own interpretation of each: I fully expect that some of you reading this may disagree!


Sustainable Drainage Systems (SuDS): A principle for surface water management only really used in the UK and Ireland, based on managing surface water as close as possible to where it falls by mimicking natural paths and processes. SuDS fulfil the joint objectives of quality, quantity and amenity using a wide toolbox of techniques (manufactured or ‘natural’) to deliver attenuation, infiltration, flow control and water treatment.


Water Sensitive Urban Design (WSUD) is a much more global term used to describe an approach to planning and designing towns and cities through integrated and sustainable approaches to water management. It looks at the water cycle as a whole and how urban environments can best be developed to bring about healthy ecosystems by integrating the whole water cycle.


I believe Green Infrastructure (GI) began life in the US alongside terms like Low Impact Development (LID). For me GI is simply a way of describing surface engineering techniques that favour ‘natural’ or ‘green’ features. It can also be expanded to describe a way of linking green ‘corridors’ or spaces through urban and rural environments to build a countrywide green network to connect ecosystems and encourage biodiversity. 


Introducing the term Blue Infrastructure links the concept of water to GI. Essentially blue corridors, or a network of water bodies, are intimately connected with green corridors. The ‘blue’ environment can encompass natural watercourses, lakes and ponds as well as man-made water bodies and manufactured drainage features.


It’s easy to recognise the vision that connects these concepts and gets people passionate. Using the opportunities that water presents to ‘green’ more of our public spaces can help our urban environments to breathe again. Reconnecting the need to conserve water with a need to recycle rainwater is a ‘no brainer’; we simply must stop wastefully sending useable surface water to sewers.


But with all of this well-intentioned passion come challenges of practicality and step-by-step progress:  At the beginning of this blog I said we needed to go ‘back to basics’ by reconnecting the water cycle. But that does not necessarily mean back to nature all by itself.


My concern is that a passion for ‘green’ has become the sub-text for some of these terms and a platform to evangelise ‘natural’ as the default solution. After all, mankind has spent hundreds of years improving on nature and all infrastructure is engineered in some way. Are we at risk of developing a kind of pre-industrial preference for ‘green’ that excludes well-proven technologies that can help deliver sustainable – and practical – answers to urban problems?


Our construction industry is bearing the brunt of a stagnant economy and for many developers and contractors futuristic concepts of water-sensitive cities are little more than pipe dreams, compared to a day-to-day battle to stay profitable.


No doubt, the debate about terminology will continue. You could say, at the end of the day, the language is not that important. What is important is that an idealistic interpretation of SuDS doesn’t discourage shovel-ready projects and slow down the introduction of more sustainable water management practices that are still a huge improvement on the status quo.

  • Gary Grant

    Although it may be true that many developers and contractors are not interested in GI that should not deflect us from the need to educate. Best practice and working with nature has a place no matter what state the economy is in. Also I am not convinced that mankind has spent hundreds of years improving on nature in terms of drainage and urban planning – more like a series of usually crude short term fixes.

  • RAshley

    I do like the pipe dreams bit… The most important aspect is that surface water is a resource and an opportunity NOT to be seen as a problem to be dealt with. Hence it should not be considered something to be managed rather surface water needs to be exploited.

  • Kevin Barton

    Alex – Nice article.

    I like your simple definitions, although we have always ‘stretched’ the definition of SuDS for our projects, including rainwater harvesting, recycling and treatment of

    Personally, I think we should have just one hook to hang the sustainability of water on as SuDS, rainwater harvesting and recycling, aquatic ecosystems and the water cycle are so interconnected.

    Also, can you expend on your concerns about the ”green’ subtext’, evangelising ‘natural’ and what an ‘idealistic’ interpretation of SuDS is? As I was reading this, I can’t quite visualise what your fears are – where would the idealistic approach take
    us that is so threatening?

  • Paul Shaffer (Dee)

    Alex Thanks for a thought provoking blog.

    As a facilitator often accused of being too green or favouring manufacturers I found the argument in the blog and subsequent comments really interesting.

    I’m a firm believer of working to the opportunities and constraints of a
    site. Wherever possible managing surface water on the surface and close to its
    source has to be preferred. The growing body of evidence suggests the benefits
    and opportunities are huge (Ecosystem Services, Green Infrastructure valuation etc etc) – it’s not idealism, it’s a preferred approach. That said, I recognise this may not always be possible and this where underground, proprietary products come in there own. Horses for courses.

    The terminology should not be seen as a barrier to delivering a solution
    that provides the most benefit in the context of the site and budget. There’s
    commonality in the terminology that good design delivers better places… deals
    with a challenge (of flood risk, water quality) and provides opportunities for multiple benefits. Which in this day an age can bring different people together to fund and manage different interventions. There’s a place for all approaches.

    Getting accusations of being too green or product friendly probably means I have the balance about right.
    Interesting discussion

  • @hydro_alex

    Folks – thanks for the comments and apologies for not being able to come back sooner. I was hoping that the blog would generate some interest as this is a topic close to my heart. Briefly taking the comments made so far :-

    Gary – you’re dead right, but the only comment I would make is in defence of developers who I think get a bit of a bad press sometimes for wanting to make a profit. I think we all want, or indeed need, our own individual organisations to survive and at least not lose money and developers are no different so when they see they may be being forced down a route where the they perceive they may have to donate valuable land to incorporate often large, natural features, I can understand their concerns to a certain extent. Having said that, there are many excellent examples of where the right balance has been achieved between a vision and enabling practical
    approaches (sometimes using proprietary devices as the enabler) that have ‘got
    the job done’ and have made the most of all opportunities.

    Richard – excellent point. Despite the many good examples mentioned above, there are still very few instances of where surface water is being treated as a resource or exploited in a satisfactory manner. If I’m wrong on this and anyone has any good case studies, I’m sure Paul and Susdrain would love to see them and include them on the website.

    Kevin – I like your suggestion of ‘one hook’ – perhaps a topic for another blog or even a competition!
    In response to your request for clarification about my concerns, the reason I
    mentioned this in my blog is mainly down to my frustrations when dealing with the many projects, seminars and workshops we get involved in where there appears to be a mentality, at least amongst some, that requires all SuDS systems to be solely above ground, green and natural. I have been an avid supporter of authentic, attractive, aesthetically pleasing, natural SuDS schemes for many years but I know from experience that sometimes the only way to deliver these is through the inclusion of engineered or proprietary elements and this often seems to go unnoticed or even discouraged on the grounds that anything underground or out of site is either more expensive to maintain or will not be maintained at all. I would suggest that there is no such thing as a maintenance free SuDS system and there are plenty of natural, above ground SuDS installations that have not been maintained, or even built as designed, and to get them back to a condition where they will perform as intended will be a
    major operation and very expensive.

    Paul – I agree – Horses for courses – another great title for a blog!

  • David Singleton

    Alex – some good stuff here! I think we’d all agree that balance is of the essence and it all really comes back to design. Get poor design (and indifferent designers) and no amount of terminology will help you. If you are to get excellence in design (rather than simply expedient ‘solutions’) I think a good dose of idealism is needed. I haven’t yet come across a scheme where a shovel-ready project was stalled by idealism. Routinely the ideal is watered down into something that the builder is happy with. And the search for the ideal continues to the next project!

    I’d offer that when developers get a bad press they sometimes deserve it, for building soulless stuff that misses opportunities and contributes to poor places. It is common in spatial planning to require land to be allocated for ‘non development’ uses, be it private gardens (and now allotments), public space, ecological corridors, play areas, highways or whatever, including SuDS. Nothing new or scary there.

    Anyone who doesn’t recognise the likely need for at least some ‘structures’ in SuDS on any scale hasn’t built any. There are examples (we are working on several at the moment) where buried structures can help realise a scheme. Let these examples be celebrated. We’ll have at least one to Paul before Christmas.

    You ask, ‘Are we at risk of developing a kind of pre-industrial preference for ‘green’ that excludes well-proven technologies that can help deliver sustainable – and practical – answers to urban problems?’ No, I don’t think so. Not here, nor in any other country I’ve experience of. People don’t tend to ignore well-proven technology.

    There is a considerable danger that buried ‘solutions’ are pushed hard in order to shift product or because it offers a ‘neater’ solution. We have had experience of this also. One example featured a housebuilder who, despite having to allocate one third of his land to green space, (and accepting this totally) insisted that SuDS had to be buried under car parking. When we (on behalf of the LPA) examined this with him, he admitted that this was, in fact, nonsensical and liable to be costly. It appears that the option of using the allocated green space to accommodate water hadn’t even been explored, such was the fixation, in this case, with tanks. This must change if we are to lead towards the sort of places that good SuDS design offers I think you’d agree.

    You are right that there are few examples where water is being treated as a resource. This is new, water is cheap and plentiful (at least in UK at the moment) and it takes time (and incentives) to change. See susdrain case studies Forest Way School and MV16, Melton. Both projects use rainwater harvesting.

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