‘On Every Roof Something is Possible’: How Sponge Cities Could Change the Way We Handle Rain
Sourced from The Guardian
You might visit Amsterdam for its canals, and who could blame you, really. But the truly interesting waterways aren’t under your feet – they’re above your head.
Beautiful green roofs have popped up all over the world: specially selected plants growing on structures designed to manage the extra weight of biomass. Amsterdam has taken that one step further with blue-green roofs, specially designed to capture rainwater. One project, the resilience network of smart, innovative, climate-adaptive rooftops (Resilio), has covered more than 9,000 sq metres (100,000 sq ft) of Amsterdam’s roofs, including 8,000 sq metres on social housing complexes. Citywide, the blue-green roof coverage is even bigger, estimated at more than 45,000 sq metres.
The “sponge city” concept is becoming increasingly popular. Planners deploy more green spaces that soak up downpours that are getting heavier as the world warms. That simultaneously reduces flooding and recharges the underlying layer of absorbent rock, which can then be tapped into in times of need. Whereas cities used to be designed to divert rainwater away as quickly as possible, increasingly, they are exploiting that resource.
A big challenge with sponge cities is that so much of an urban area is rooftops. Green roofs will soak up some rainwater to hydrate the plants there, but blue-green roofs go a step further, with infrastructure that gathers the liquid, stores it and dispenses it to the building’s residents for watering plants and flushing toilets.
The system works in layers. At the surface, you have plants: some combination of mosses, shrubs, grasses, ferns, herbs and sedum, a hardy genus that’s a staple of green roofs. (While plants need sunlight to survive, on a roof, they can be bombarded with too much light. It can also get hot and windy up there.) The plants are rooted in soil, providing nutrients and support.
From the Living Architecture Monitor
