Fishermen say the Mamallan Reservoir plan ignores the risks of tidal flooding

Representatives of the Save Nemmeli Marshlands campaign, fishermen, environmentalists and conservationists urged the state government to drop the proposed Mamallan reservoir project at a press conference in Chennai on Monday. | Photo credit: SR RAGHUNATHAN

Traditional fishermen from villages along the Kovalam sub-basin on Monday urged the state government to abandon the proposed Mamallan reservoir project, alleging that it was designed without adequate consideration of tidal movements and storms from the Bay of Bengal.

At a press conference organized by the Save Nemmeli Marshlands campaign, fishermen, environmentalists and conservationists said the government-commissioned Integrated Coastal Zone Management Plan, funded by the World Bank, indicated that much of the proposed ‘uppankazhi’ salt marsh reservoir site would be inundated by 3.5 to 4.5 meters of seawater during heavy storms.

They argued that the Water Resources Department’s (WRD) proposal and the technical assessment by the Indian Institute of Technology Madras (IIT-M), submitted in support of the Coastal Regulatory Zone (CRZ) permit, did not adequately assess this risk.

S. Mohana of Periya Nemmeli said families dependent on shrimp fishing fear loss of livelihood if the dam comes up. “We depend on shrimp fishing in these backwaters. If the reservoir is built, we will lose all our livelihoods,” she said.

She expressed concern that during heavy rain, strong tidal waves are already pushing seawater into the backwaters and a reservoir in the area could pose additional risks to nearby residents. “It is dangerous to build a reservoir near the sea. It is not the same as building a reservoir on a river. Our whole life depends on the sea, we know that. This should not be done,” she said.

R. Narayanan, a traditional fisherman from Kovalam, said local communities have been witnessing seawater intrusion into the marsh during spring tides and monsoon for decades. He argued that the proposed dam would not prevent seawater from entering the reservoir.

Speakers said that while the IIT-M assessment examined freshwater inflows from the western basin, it considered the sea only as an outflow of excess floodwater. They said the proposed outlets to discharge excess water into the Bay of Bengal could instead allow seawater to enter the reservoir during storm surges.

KV Sudhakar, president of the Madras Naturalists’ Society, said the wetland is an irreplaceable ecosystem supporting rich biodiversity throughout the year. Bird surveys conducted in the Kelambakkam-Kovalam-Nemmeli landscape between 2022 and 2025 recorded between 107 and 137 bird species annually. “Even during the dry season, the marshes are vital for more than 135 species, which include migratory species, endemic species, IUCN Red List species,” he said.

The speakers further warned that converting the marsh into a reservoir would remove about 4,375 acres of natural flood storage, increasing the risk of flooding in nearby areas such as Thaiyur, Kelambakkam, Thiruvidanthai, Padur, Pattipulam, Saluvankuppam and Mamallapuram.

Published – 20 Jul 2026 20:12 IST