The project will include construction of mini ponds and trenches at the parks. The trenches will carry water from roads and storm water drains into the ponds.
Corporation chief engineer S Rajendiran said they wanted to find solutions for not just floods but also droughts. “We want localities to be self-sufficient to prevent street flooding. The move will also recharge ground water. The water can also be used for drinking purposes in extreme situations,” he said.
An engineer in-charge of the work said the pond will be surrounded by a wall and stone pitching along with a fencing for safety. Inlets into the ponds from the storm water drains, roads and sides of the parks and outlet chambers will also be set up for removing excess water.
Rainwater harvesting structures with well rings inside the ponds to allow ground water percolation, tree plantation around the ponds, necessary lighting and benches around the ponds will also be done, the official said.
Experts said while the intention is good, by adding mini ponds alone, these parks cannot be called as ‘sponge parks’. The civic body engineers need to study the entire drainage pattern of the area to make it a holistic solution.
Manushi Jain, director of Sponge Collaborative, an expert in sponge parks said, “There are three layers – green, blue and social layer making it beneficial at several levels. Sponge parks should go beyond flood mitigation and bring in communities, creating a space for them using resilient infrastructure. It requires more green cover that will bring in a lot of biodiversity as well.”
Residents suggested SWD connections may lead to illegal sewage entering the ponds and that needs to be stopped unless the parks have a sewage treatment plant.
Water expert and project leader of South Asia Consortium for Interdisciplinary Water Resources Studies S Janagarajan said sponge city itself is a global concept and most cities are adopting the technique to find nature-based solution for flooding.
“I’m glad they are adopting this concept. This won’t eradicate flood risk but only reduce it as it is a holding-water pond. The civic body should use appropriate method. Water from inundated streets could also be pumped into these ponds,” he said.