Head Over Water
How cities can manage an abundance of water
Stormwater is an increasing urban issue. During the 20th century most urban areas were paved with hard non-permeable surfaces, leaving stormwater and floodwater nowhere to go if it reaches the city.
The wall
Water can be walled out. Most of the time it succeeds, sometimes it fails.
Walls can also protect sinking cities.
Walls don’t help if the water comes from inside the city. Then a different approach is needed.
The sponge
This is where we started. With major rainfall the challenge is to prevent it from accumulating where it does major damage.
One approach is to slow the water down. Vegetation has evolved to absorb and slowly release water, and a favourite solution not just to handle stormwater, but also to cool cities down i heatwaves.
And they reduce air pollution, improve wellbeing and mental health.
Although it has long been understood that green and blue spaces play an important role in addressing both human and ecosystem health, it has only been in recent times that these relationships have been specifically investigated. This has become even more important within the context of needing to adapt planning and land use to several social and environmental challenges, such as urban deprivation, biodiversity loss, pollution and climate change.
The drain
While water can be slowed down, it still needs to go somewhere, usually a river, a lake or the sea. If the water arrives faster than it can be diverted there, a temporary storage is needed.
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Tokyo has gone to one extreme, but water stores either underground in cisterns or above ground in flood plains.
Many regions in the world, particularly the urban ones, are water stressed. Water is a valuable, sometimes critical, resource. For that reason stormwater should not merge with the sewage system, particularly as we run the risk of it overflowing.
The stilts
This is one of the oldest way to build in Europe, though more for protection from other people than from stormwater and floodwater. Venice grew into a city for much the same reason.
Elevated floors is a good way to build on flood plains, though it has for a long time been out of fashion in Europe.
Ground floor can be used for transient, mobile, recreational, social, flexible purposes, anything from a garage to a dining area. There are usually days of warning before a flood, but only hours or less for stormwater.
The float
If you can’t beat it, you can rise above it.
Unlike houseboats, floating homes are fixed to the ground, but will rise up or sink to the current water level.
The Danish BIG architect firm and the US startup Oceanix go one further to plan whole city districts on water.
The obvious disadvantage, apart from floating buildings not alleviating flooding elsewhere, is the cost. This is a working solution for those who can pay for it, and does nothing for the rest. That said, to the extent there will be floating public buildings, they could offer shelter over water for those who would otherwise be under water.
For cities with a limited budget, the solutions are going to be green (vegetation) and gray (drainage), not blue.
