Water logged roads, endless traffic jams have become par for the course on rainy days in cities across the world. In Indian cities, the growing volume of cars, burgeoning urban populations, and massive rise in built-up areas have only made rainy days a nightmare. Add to that the growing threat of extreme rainfall events, which are bound to increase in periodicity and intensity on account of climate change.
But with competing demands on space, local governments in cities like Delhi, Mumbai, Bangalore or Kolkata are finding it difficult to address this new problem. The port city of Rotterdam in The Netherlands provides interesting solutions to managing and storing excess water. Rotterdam faces all these challenges and one more— it is six metres below sea level. Located in the delta of the Rhine and Meuse rivers, nearly 90% of the Dutch port city is below sea level.
So it isn't just heavy rains that threaten Rotterdam, the rising sea level makes it imperative for the city to find ways to ensure that excess water keeps flowing out. In 2008, the Rotterdam city administration took a decision to climate proof the city.
"It was a paradigm shift, how to combine urban design with adapting to climate change," explained Arnoud Molenaar, manager of the city's climate initiative, Rotterdam Climate Proof. Molenaar explained that in dealing with heavy and extreme rainfall that was becoming more common due to climate change, the city had to find a way to control the flooding.
"We are a country that has always invested in keeping the water out, but sometimes that is not enough, it was necessary to find ways to manage the water." The trick that Rotterdam mayor Ahmed Aboutaleb realized was to show the city the opportunities that climate initiatives presented— hence the idea of an urban public space, underground parking and rowing track, all of which double up as water storage areas.
BENTHEMPLEIN WATER SQUARE
On a regular sunny day, Benthemplein looks like any other urban space— a colourfully done up open space. With its basketball hoops and amphitheatre like seating, the square doubles up as an open play space for the adjoining school or another spot where the school goers can hang out at break time. But Benthemplein is no ordinary public square.
On a rainy day when it seems that roads will be waterlogged, Benthemplein doubles up as rain water storage area. The sunk-in design, which allows for the amphitheatre like seating, helps transform the "square" into a water storage area. The two additional basins, which are located on either side of the main square fill up first. These have sloping edges which allow for the overflow from the steel gutters to be collected. The water remains in a temporary storage area before moving through the sewage and water pipes through the treatment units and finally into the nearest water body without overburdening the system.
"The underground is so packed that there is no way to put in more pipes to deal with the excess water. So, we needed a system that would take the water off the streets and let it move slowly into the water canals," explained Arnoud Molenaar. Designed by the Rotterdam-based architecture firm, DeUrbanisten, the Benthemplein water square can hold up to 1700 cubic metres of water. The square was built at a cost of 2.5 million euros, with a subsidy of 1.2 million euros from the European Commission.
UNDERGROUND PARKING AND WATER STORAGE AT MUSEUMPARK
There is more to this underground car park than meets the eye—it has an underground storage facility with a capacity to store 10,000 cubic metre. The water is kept in this storage area and later pumped into the sewers, and treated for release into water canals when the system is no longer under pressure.
The storage was built at a cost of 11 million euros, and utilized a section of the underground parking that could not be used for cars, explained Bas de Wildt, advisor in the Rotterdam city's public works departments. Besides relieving pressure on the sewage system, this storage system ensures that untreated sewage water is not released into the water canals during the rains. The city's water management system relies heavily on canals.
"But when there is heavy rains, it is difficult to pump the rain water into the system fast enough,' de Wildt explained. The underground system allowed for a way out to hold the excess water in an unobtrusive manner till it could be treated and released."
WILLEM-ALEXANDER BAAN ROWING COURSE
The Willem-Alexander Baan, located 20 minutes by road from Rotterdam, in the Eendragtspolder, is another example of multifunctional approach to water storage - an international rowing track which is really a 300 hectare water storage area.
