Making large campuses resilient to heavy rain
‘RWH structure should be installed based on soil profile’
With the intense spell of rain like the one witnessed in November likely to become a frequent phenomenon owing to climate change, experts stressed on the need to make large open spaces more resilient to floods.
Shilesh Hariharan, principal architect at Madras Terrace, who is associated with the City of Thousand Tanks initiative, said installation and strengthening of rainwater harvesting and recharge wells must be done based on soil profile on campuses.
He said it was important to identify the region of clay, the region of sand and so on to make the percolation of water efficient. Regular maintenance of rainwater harvesting structures prior to monsoons was important.
Mr. Hariharan stressed on the need to ensure that sewage did not mix in rainwater allowed to percolate.
Kavitha Selvaraj of City Works, which has worked with Greater Chennai Corporation in designing public spaces, highlighted the need for holistic planning while designing and transforming public spaces as these spaces can play a role in recharging groundwater. She said that the tendency need not be to pump the water out from such large spaces, but give it time to percolate with adequate structures in place while at the same time ensuring that the stagnation did not lead to health hazards.
Balaji Narasimhan, a faculty at the Indian Institute of Technology Madras, however, struck a note of caution on using rainwater harvesting as the panacea. “The water table is already very high and hence is unable to absorb at the same rate as the rain is falling,” he said. The city’s flat topography with only sandy and hard rock aquifers added to the problem, he explained.
“RWH is not a magic bullet. When the underground structures get filled and the storage is full what can we do? RWH is ok for slightly below or above average rainfall, and can only help in avoiding nuisance letting,” he said.
Sekar Raghavan, director of Rain Centre, said the rainwater harvesting the State government had taken up in earnest was ironically a contributing factor to flooding this year.
He said that earlier this year, under a Rotary project, the centre was trying to construct rainwater harvesting projects in a few schools in R.A. Puram and T. Nagar. “We could not dig beyond seven feet. We could not execute the project as the water table was high,” he said. “Even at that time we knew that the first spell of northeast monsoon would flood the city,” he added.