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London, United Kingdom
I am an engineering academic at University College London where I work on the sustainability of urban water systems. I am interested in the role of engineers and technology in sustainable cities.

Saturday, 12 January 2013

Radical Drainage

What is the most radical movement in urban ecology? Transition Towns? Urban food growing? Passivhaus? Cycling? All these are significant in  changing behaviour, technology and cultures of how people who live in cities consume resources and relate to each other and their local environment. However, the movement I think is most significant in fundamentally altering the relationship between cities and the environment is to be found in the boring old world of drainage. In the UK the movement is known as Sustainable Drainage Systems (SUDS), in Australia it's called Water Sensitive Urban Design (WSUD), and in the US it's Low Impact Development (LID). Recently the benefits of new approaches to drainage have been linked to biodiversity and the need to reduce urban heat island effects, coming together under the banner of Green Infrastructure (GI). Whatever the acronym, a quiet ecological revolution is under way in the drains and waterways of cities around the world.

For the last 150 years or more, the primary aim of an urban drainage system has been to move water away from streets and homes as quickly as possible so as to prevent flooding and stagnation of polluted water close to human settlement. This fits with a modernist separation of nature and culture. Cities are for culture, nature is 'out there', in 'the wild'. Cities are where nature is tamed, controlled, mastered for human benefit. There are some very good public health reasons for this. People drown in floods, and get sick and die of water related diseases such as malaria and cholera. 'Nature' uncontrolled can be dangerous.

The problem with moving water out of cities as quickly as possible is that it has to go somewhere. It disappears down a grate in the road during a rain storm, but then where does it go? One way or another the water ends up back in the local environment. This sudden rush of water can disrupt long established patterns of flow through rivers and wetlands, and the storm water is often contaminated. Furthermore, in the rush to build drainage systems many local waterways were culverted, concreted and covered over, converted from streams into drains to become the 'lost rivers' of our cities.

SUDS, WSUD and LID all started with concerns about the impact of the discharge of urban drainage systems on local aquatic environments. Moving up the pipe they proposed that instead of getting rid of water as quickly as possible, water should be given space in the urban environment. Cities and nature are perhaps inseparable. Techniques for holding water in the urban environment and letting it infiltrate or evaporate where it falls include ponds, rain gardens, permeable paving, swales, green roofs, rainwater harvesting, and the restoration of urban rivers and wetlands. Design techniques and technologies continue to develop, but what is most important is the fundamental shift in how water, as one of the most fundamental elements of nature, is conceived. Water is no longer a danger to be controlled, but an element to be celebrated and included in the city.

The move to more sustainable draingage systems and water sensitive cities has a long way to go and many hurdles to overcome (more on that in future posts). However, this fundamental shift in how engineers, planners and urban designers, and the communities they work with, approach water in cities is of momentous significance. If sewers are the conscience of the city, as Victor Hugo said, then SUDS may be a sign of our awakening to a more ethical relationship to the ecosystems that sustain us.  

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