Less concrete, more greenery

Wageningen Climate Solutions

Photo: Shutterstock

BY Inge Janse - September 2019

It is a strange paradox: on the one hand cities are increasingly struggling with a lack of sufficient clean water, while on the other hand climate change is increasing the risk of flooding. Tim van Hattum, Climate programme manager at Wageningen University & Research, uses five propositions to explain how we can turn water from our enemy into our friend with the help of green solutions and smart technology.


“Many of today’s cities are designed to drain the water from the city as quickly as possible. Urban planners traditionally saw water as something we needed to get rid of. But more and more people are moving to the cities while the water supplies often come from a long way away. A lot of water is also needed for agriculture, industry and power generation through dams. The result is that one in four cities is now suffering from serious water scarcity.”

“Cape Town had major water shortages over the past three years due to extremely low rainfall. In 2018, the city got close to day zero, the day on which the reservoir would be empty. Rationing was introduced for the entire city with 50 litres per person per day, fines for abuses and campaigns to encourage people to save water. It worked: they just managed to prevent the city from running out of drinking water.”

“Climate change is also producing more extreme weather, with too much rain one moment and too little the next. For example, we’ve seen a huge global increase in the number of cloudbursts in the past ten years, a problem that will only become much, much greater in the future. As 90 per cent of the surface area in cities can consist of paving, asphalt and other forms of hard surfacing, the water can’t be absorbed into the ground, while the sewer systems cannot cope with such large quantities. The result is flooded streets.”

DakAkker in Rotterdam, a roof with outdoor seating and urban agriculture. Photo: Shutterstock


Climate change is producing extreme weather, with too much rain one moment and too little the next

“All urban councils want to make their cities greener. That has a major impact in making the city pleasanter to live in and more attractive to businesses. Greenery also helps make water management more climate-proof: saving every last drop for the city rather than draining it as quickly as possible.”

“You can design a city to act like a sponge, absorbing the rain where it falls, whether that is your garden, roof or street. If that is not possible, you need to set up green zones where the water is collected and stored, for example a water square.”

Benthemplein in Rotterdam is a ‘water square’: when the weather is dry, you can play basketball or go inline skating there, but it turns into a shallow pool whenever there is heavy rain. Photo: David Rozing, Hollandse Hoogte


“We still often view cities from a civil engineering perspective, trying to control water using underground pipes. Fortunately that traditional approach is starting to change, and climate change is accelerating that process. The expense is another obstacle, as storing water instead of draining it costs money. Ideally you would see budget being reallocated from the municipal sewerage department to the municipal parks department because the more greenery you have, the fewer sewers you need. But the funding is segregated and departments still have a tendency to compartmentalize. So we need much more integrated concepts for water management in the city.”

“There is also a lot of demand for knowledge about greenery. How effective is the greenery exactly and what kind of vegetation are you best off using? Should you focus on trees, for instance, because they provide shade and let water evaporate? And how can the vegetation best help boost biodiversity? WUR has long recognized the importance of greenery in cities for nature, biodiversity and the people who live there. Greenery makes people happier, calmer, healthier and less stressed.”

Greenery helps make water management more climate-proof: saving every last drop for the city rather than draining it

WUR researcher Tim van Hattum shows some good examples of smart urban development in the Netherlands.


The trick is to consider what would be a smart design for the city of the future every time you start excavation

“Builders and landscape architects need to think hard about how to make designs and structures that are climate-adaptive and nature-inclusive. What they build now will be around for a century or more. But a lot is already being asked of the construction industry. It has to be part of the circular economy, energy-neutral and safe, and now we are adding ‘climate-proof’ through the widespread use of vegetation. On the other hand, builders can make a difference precisely by taking an integrated approach.”

“There are huge opportunities here too because the Netherlands needs to build one million new houses by 2030, many of which will be in the cities. The trick is to consider what would be a smart, nature-inclusive and climate-proof design for the city of the future every time you start excavation for new homes or sewerage systems. Every time you fail to do that now means you will have to wait 40 to 50 years before you get another chance.”

Gardens by the Bay, a nature park in Singapore. In that country, they get maximum use out of every drop of rain. Photo: S-F / Shutterstock


“The Netherlands is not yet one of the frontrunners internationally. My favourite example is Singapore, a city-state with no water sources of its own. So the administration said, let’s turn our city into a nature area so we get maximum use from every drop of water that falls. They developed a lot of technology to do this, even making the sewage water drinkable again.”

“But I certainly don’t want to give the impression of a major tragedy because there are already plenty of great examples here in the Netherlands. For example, WUR has joined forces with a number of other parties in a programme to encourage people to replace the paving in their gardens with greenery. That is a must as there’ll be no place for paved gardens in the new urban designs.”

“Many places in the Netherlands are also looking into green roofs — roofs covered in vegetation that can absorb the rainwater. In Rotterdam you have DakAkker, a roof with a seating area and urban agriculture.”

“We did a pilot project in Arnhem with smart water management after the city had problems dealing with heavy rainstorms in 2014. There is now a water storage area on the city periphery. If it rains hard, the water is held there. It would be a shame to let that water flow into the Linge when you need it again in dry periods. We have developed a model that uses smart sensors and weather forecasts to predict when it will rain. If there is a shower, the water storage system automatically empties so as to maximize the available capacity. A scaled-down version of that approach can also be used on green roofs.”

“This is the direction we should be going in more: green measures like this that significantly improve the quality of life in cities and make use of smart technology for water management. There are still a lot of questions, though. What are the costs and benefits? What tree species thrive in the new climate? And how can you get the general public involved? More research is needed to answer these and many other questions.”

For more information about WUR’s research on the climate-adaptive city, please visit our website.

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