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How to make a city waterproof

How to make a city waterproof

In the age of climate change, Rotterdam has become the world’s most important testing ground for urban design

In the age of climate change, Rotterdam has become the world’s most important testing ground for urban design

Giovanna Dunmall | June/July 2018

One evening in March, a pale-blue layer of light began spreading across the plaza outside the United Nations headquarters in New York. Emanating from banks of leds, it appeared to undulate like the surface of the sea high above the heads of passing pedestrians. The effect may have been ethereal but the warning was all too real: the light submerged the plaza to the same depth that water may do if nothing is done to control rising sea levels.

Called “Waterlicht” (Waterlight), the installation was the work of Daan Roosegaarde, a Dutch artist; New York was just one stop on a tour of global cities. Roosegaarde’s intention is to focus people’s minds on the prospect of a watery future. “Above all it gets people who might never do so talking about water and global warming,” he says. Often the conversation turns to keeping water out. But increasingly urban planners and designers are taking their cues from Rotterdam, the city where Roosegaarde lives and works: they are working out how to let water in.

Like thousands of coastal cities from Shanghai to Miami, Osaka to New York, Rotterdam is under threat. More than 80% of this port on the Netherlands’ North Sea coast lies below sea level, the ocean kept at bay by a sophisticated system of levees, dykes, dams and storm-surge barriers known as the Delta Works. But by the end of the century those sea levels are predicted to rise by around a metre and the Netherlands is already seeing an increase in rainfall and flooding. To make matters worse, the thousands of pumps that remove groundwater up and down the country are causing the peat to dehydrate and the ground to sink. In recent years this has led to a shift in thinking: instead of working against the water, why not re-engineer the city to work with it?

At first glance, Rotterdam’s Benthemplein (below) looks like a pleasant but ordinary city square. It has a basketball court, skateboarding ramps and benches. Look a little closer, however, and you begin to notice an array of wide, stainless-steel gutters zig-zagging around it; striking green, white and blue water-themed patterns on the ground; and two shallow basins that appear to feed into the basketball court, which is surrounded by stepped seating.

Benthemplein is actually one of five water plazas in Rotterdam and was designed by De Urbanisten, an architecture firm based in the city. A receptacle for up to 1.7m litres of excess water, it funnels the flow from surrounding streets and rooftops. When heavy rain comes the two smaller basins fill up before feeding a third, deeper one, their contents gushing over a beautiful “water wall”. In dry weather the square, which is also planted with tall grasses and shrubs, is a buzzing hub. In wet weather it becomes an inner-city lake.

Pooling ideas Benthemplein, one of Rotterdam‘s five water plazas

Water plazas are part of a wave of development in the city that thinks of climate change as a spur to innovative urban design, and it has turned Rotterdam into the world’s most influential testing ground for life in a water-filled future. Rotterdam is home to the new Global Centre of Excellence on Climate Adaptation, a joint project between the Netherlands, the United Nations and Japan, and every year more than 100 international delegations visit to see how architects and designers are reimagining the city. “Our new philosophy”, says Arnoud Molenaar, Rotterdam’s chief resilience officer, “is to not look at climate change only as a problem.”

The focus for these experiments is Zomerhofkwartier (Zoho for short), a district just north of the city centre. As well as large public projects like the water squares, small-scale schemes can be seen at every turn. The streets have been partly “depaved” and replaced with vegetation or decorative tiles designed by Fien Dekker, a graduate of the Eindhoven Design Academy, that capture and store water in deep, intricate rivulets before letting it seep slowly into the ground. A “rain garden” has been carved out of old parking spaces, designed to gather water as it flows over the tarmac complete with pathways, stepping stones and beds planted with species that thrive in wet ground. A timber sign spelling out “zoho” in giant letters doubles up as a rainwater storage system: each letter is a barrel.

Elsewhere the city is spreading out onto the water. Pieter Figdor of Public Domain Architects is designing a neighbourhood of floating homes in Nassauhaven, one of three old harbours being transformed for housing. Each lightweight aluminium-framed and timber-clad home will float on a platform of concrete and polystyrene that Figdor describes as “unsinkable” – which is just as well, since this part of the river has no protection from dykes or flood defences. The houses will rise and fall by about two metres a day with the ebb and flow of the tides. “You won’t even notice it,” says Figdor. “You will just see at some point that your view has changed.”

More radical is the world’s first floating dairy farm in Rotterdam’s Merwehaven harbour, due to open in September. Peter van Wingerden, a developer who specialises in floating structures, was inspired to take on this project after Hurricane Sandy, which struck New York in 2012 and flooded streets and subway tunnels. “People we met in New York talked about how the city shut down and there was no fresh food in the shops for days,” he says. The hi-tech €2.5m floating farm is a two-storey, 1,200-square-metre platform that will produce 1,000 litres of milk a day to be immediately pasteurised and processed into milk, yogurt and cheese in the dairy one storey down. A herd of 40 cows will spend their days on a tree-filled, water-borne meadow. The system, says van Wingerden, is “closed loop and completely unaffected by rain or flooding”. Next he plans to open a floating chicken-farm and a floating greenhouse.

Rotterdam’s ideas are spreading. Philadelphia has embarked on a $2.5bn, 25-year initiative to install 19 square miles of rain gardens and permeable surfaces to alleviate flooding in the city. Figdor’s firm is working on a floating offshore harbour for the seaport city of Chittagong in flood-afflicted Bangladesh. Meanwhile, Copenhagen is getting its own version of a water plaza in the district of Vesterbro, where Flemming Rafn Thomsen, a founding partner at Tredje Natur, an architecture practice, is transforming a neoclassical park. The scheme involves a dyke that doubles up as seating around the perimeter of the park. It will capture water and direct it towards low-lying gardens and sunken sports pitches, which will become temporary water features and lakes. The firm’s most visionary idea, though, is called Pop-up: an underground car park that will rise above the streets as storm water fills the cavity beneath it. Though, for now, it exists only on paper, its ingenuity has garnered attention. “We were getting more likes on social media than Michael Jordan’s new sneakers!” Rafn Thomsen says. “Utility companies are funding huge underground emergency reservoirs that are only going to be used 1% of the time, while cities are struggling to provide parking and homes,” he says. “This is about thinking in a more unified way.”