I’m standing in the middle of an unusual public square in Rotterdam. To my left is a drama school with an imposing concrete entrance and a sprawling plaza. To my right is a trio of large sunken squares, each ringed by a few steps.
On a regular day like today, these squares can be used as basketball and volleyball courts, skateboarding rinks, amphitheaters, or even ceremonies for the nearby church. But when it rains, the squares can fill up and hold up to 450,000 gallons of water.
The Water Square (Waterplein in Dutch) was designed by local urbanism and landscape architecture firm De Urbanisten. It was completed in 2013, and it marked a shift in the firm’s mission. Since then, the architects have researched water management issues in Mexico City; Antwerp, Belgium; and even New York City in the aftermath of Hurricane Sandy. They’ve built another water square in the Dutch town of Tiel, a sponge garden outside their office in Rotterdam, and now they’re working on two major projects elsewhere in Rotterdam: a tidal park that was designed to flood, and a climate-adaptive version of Manhattan’s High Line, complete with a water-purifying landscape.
At the core of De Urbanisten’s practice is the belief that landscape architecture can help mitigate climate change by moving away from obsolescent drainage systems and toward more natural approaches like rain gardens and permeable surfaces.
The studio’s work is particularly crucial in Rotterdam, much of which lies below sea level. But as climate change makes flash floods and extreme rainfall more likely across the globe, it offers a replicable model that extends far beyond the limits of the city.
“The drainage city is a 19th-century concept that was elaborated in the 20th century, but we’re not going to bring that into the 21st century,” says Dirk van Peijpe, a founder of De Urbanisten. “We still might need a little bit of these pipes and pumps, but we have to start investing in a future system that is a nature-based system with soil and blue-green infrastructures.”
In 2019, De Urbanisten created a small sponge garden designed to soak up rainwater quickly, hold it temporarily, and release it back into the ground slowly. For the past three years, the architects have been using the garden as a testing ground, trialing various plants and soil compositions like clay, rubble, and peat.
Agate Kalnpure, an architect and landscape designer at the firm who took me on a tour of the sponge garden, says the garden isn’t connected to the city’s sewage system. Instead, it can collect and absorb stormwater without anyone having to water the plants. The concept can be scaled and replicated across a wild variety of urban scenarios, from residential gardens to landscaped strips alongside highways.
Not far from the sponge garden, De Urbanisten is working on a tidal park. Located right at the edge of the river in a former harbor, the park—or parts of it—was designed to flood with the tide, about twice a day. The concept was developed with the municipality of Rotterdam as a blueprint for a wider initiative that would see much bigger stretches of the riverfront transformed into a tidal park.
Rotterdam has more than 220 miles of river banks, but 70% of those are lined with hard quays and built-up residential areas right on the water’s edge. The tidal park will provide what van Peijpe calls “soft ecological spaces” with increased biodiversity that was pushed out by the polluting harbor.
It will also increase flood resilience as the terraced, vegetated slope of the river bank can help break the waves when water levels are high. On a regular day, parts of the park would be accessible at low tide, helping reconnect citizens with the river and the renewed variety of animals that would be drawn to the underwater life.
This level of coexistence is important and suggests that public spaces can do double duty. A park can also provide a natural defense against floods, and a set of public squares can also act as rainwater storage.
Back on the Water Square, the architects had to disconnect the plaza from the city’s sewage system. During flash floods, a network of oversize stainless steel gutters built into the pavement channel rainwater into the three ponds, then to an underground infiltration basin that filters pollutants and lets the water soak back up into the soil.
Wait a few years, and the Water Square will be part of a much larger network of public spaces and parks that will be linked by a green spine hovering above the city. Rotterdam’s version of the High Line is called Hofbogenpark, and it will sit on top of a 1.2-mile abandoned railway viaduct.
When the park is completed, it will feature a robust, circular water management system: Rainwater will be purified naturally through the soil on the roof, then sent to an aquifer via underground drainage pipes, where it will be stored and then reused to irrigate the park’s landscape. Most of the park will also feature a water stream for kids to play in.
Eventually, van Peijpe envisions, there will be something he calls a “rainwater cascade” scheme where rainwater would be collected and gradually absorbed at various points throughout the city—first on the roof, then through gardens surrounding the building, then on permeable surfaces along the sidewalk, and then through a variety of systems from water squares to sponge parks, until, finally, the water slowly seeps into the ground and disappears.