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On rain and gardens (Water in the city 1/100)

A drought caused the Great Stink in London in 1858: the hot spell caused an awful smell and coincided with several cholera outbreaks. This episode is considered a turning point in the history of urban waters. Until that day, water had been the richness of the cities, a resource to be celebrated with beautiful fountains. After the Great Stink, water needed to be hidden from the site, insulated from urban noses and longs. A triumph of civil engineering, commanded by Joseph Bazalgette, ensued and dominated the practice of city building and urban expansion. Water is piped as soon as possible - if we could, we would erect funnel towers to grab it closer to the sky - brought to a purification plant and then released, clean, in water bodies. We became so efficient at managing water that we started overdoing it: all rainwater was piped away too, to avoid the risk of flooding and keep the streets clean. The water disappeared from the city and even from the manuals of urban planners and designers. The result is that less and less water stays in the ground, replenishes the water tables and feeds rivers.

Water and Urbanism Unagru Architecture Urbanism
Section of the Victoria Embankment. Urban design and infrastructure in one.

Exponential urban expansion has exacerbated the issue with more impermeable surfaces: the water falling on them is again collected in pipes and directed to the closest water body. Intensive and extensive agriculture has reduced tree coverage and made the existing water bodies more vulnerable. Climate change is making things worse: shorter rain events (with the associated risk of flooding) are spreading apart more. Combining these three processes explains the images of the river Po, the longest and most extensive in Italy, reduced to a streamlet.

The disappearance of water is a massive loss and risk for us all, from an environmental perspective and the quality of the space we live in. Water could play a central role in harmonising the relationship between built and unbuilt, reminding us of the shape of the landscape and structuring different parts of the city as it had done traditionally. Fortunately, water's importance is returning to the centre of the design debate. It was a central theme in my PhD and is the core of the Design Unit I co-lead at Cardiff University's MAAD . Our ability to act at even the tiniest scale, to affect significant and complex systems, often escapes most designers. And given that my mission is to expand the agency of ecological design and designers, I want to dedicate some time to tools that can help us create beautiful ecological designs at every scale.

There are several ways to adapt and improve the water cycle in our urban age. From replacing a tap to wonderful and complex urban ecology projects, we love to be involved. I like to start with simple things, so I'm going to dedicate a new post every month to systems that help manage water sustainably, often called SUDS: sustainable urban drainage systems. They are meant to collect, purify, store, and slowly release water into the ground.

  1. The SUDS principle is simple: we should safely retain as much clean water as possible into the ground. This strategy’s advantages are reducing pressure on the sewage system and the risk of flooding.

  2. Reduce stress on the purification plants. These have a maximum operating capacity, beyond which they release whatever is coming into our water bodies.

  3. Improve the health of the ground and the whole water system: groundwater, rivers etc.

  4. In many cases, by providing open spaces to collect water, SUDS give the grounds for new ecosystems and an increase in biodiversity.

No solution is too small, and the smallest of all, the leaky water butt - is so bright and efficient that it should be free and mandatory for every building. In this post, we will discuss an alternative water harvesting design: the rain garden. Or better, the hybrid rain-harvest garden we designed for our dear friends Amell and Antony.

Water harvesting means simply storing (usually) rainwater in tanks of different shapes and forms and then re-using the water (usually) for irrigation. Water gardens, instead, are shallow landscape systems or depressions in a garden, built by cleverly layering different soil types to allow the right degree of permeability and planted with species that like wet environments. They are the equivalent of a massive tank spread in a garden and teaming with beauty and life.

bromley rain gardens unagru architecture urbanism

bromley rain gardens unagru architecture urbanism

In our Bromley project, we combined the two principles to design a compact rain garden and harvesting system. We were approached to re-design the rear patio of a previously remodelled house, The Spider. We had a tight budget and high ambitions. We designed a new deck with recycled railway sleepers embedded in a concrete base – inspired by Enric Miralles’ Barcelona Cemetery. We then re-used the paving stones of the side alley to build a rain garden. The garden looks like a swimming pool, half encroaching the central concrete patio and extending onto the lower garden to form a bench and a flower bed. Rainwater from the house is collected into pipes that run under the concrete floor and into the rain garden. A small overflow re-connects back to the sewer to avoid the risk of flooding. The result is a compact but very deep, capacious rain garden filled with diverse plants and flowers. Hundreds of litres of the dirtiest and riskiest rainfall are not passing through the sewer system, reducing flood risk. Hundreds of litres of rainwater slowly seep into the ground and will help replenish the water table.

With some attention, anyone can build their rain garden. Hundreds of thousands of refuges for birds and insects, billions of litres returned to the water cycle and a healthier, happier ecosystem. What are we waiting for?

bromley rain gardens unagru architecture urbanism

bromley rain gardens unagru architecture urbanism


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