The recent floods in Kerala have revived calls to remove accumulated sediment from rivers, reservoirs and other water bodies, with concerns that reduced water-carrying capacity may have contributed to the severity of flooding.
Chief Minister V.D. Satheesan has also pointed to sediment buildup in rivers and reservoirs as one of the factors that could increase flood risks, stressing the need to examine desilting measures.
However, experts have cautioned against undertaking large-scale sediment or sand removal without proper scientific studies. Strict regulations governing river sand extraction under the Kerala Minor Mineral Concession Rules and other relevant laws have also affected the implementation of post-flood desilting projects.
Hydrologists warn that indiscriminate sand removal could have serious long-term consequences, including falling groundwater levels, degradation of riverbeds, saltwater intrusion in downstream areas and potential damage to infrastructure.
Padmalal D, a retired scientist from the National Centre for Earth Science Studies and former head of its hydrology division, said there is currently no conclusive scientific evidence to establish that widespread silt accumulation was the main cause of the recent floods.
He said the extent of sedimentation must first be scientifically established before desilting is considered a solution. According to him, natural sand deposits in riverbeds act as aquifers by storing water during the monsoon and releasing it gradually during the dry season. Excessive removal could deepen riverbeds, lower groundwater levels and eventually cause wells to dry up.
Padmalal said limited removal of loose sand from exposed sandbars during summer, known as ‘bar skimming’, is the only scientifically accepted form of controlled river sand removal. He warned that poorly planned interventions could lead to environmental consequences that may become apparent only several years later.
Manoj P. Samuel, former executive director of the Centre for Water Resources Development and Management, also called for a scientific assessment before any desilting programme is launched.
He proposed conducting a comprehensive ‘sand audit’ to determine the actual quantity of sand, silt, organic matter and waste accumulated in different stretches. Such an assessment, he said, would help identify areas where the river’s carrying capacity has significantly declined and determine where intervention is genuinely required.
Samuel suggested beginning with pilot studies in flood-prone rivers such as the Pampa, Manimala, Meenachil and Poonoor. Technologies such as bathymetric surveys and underwater drones could be used to accurately map riverbeds and assess sediment accumulation.
Experts therefore stress that Kerala’s focus should be on scientific assessment and targeted intervention rather than indiscriminate desilting, particularly as the state seeks long-term solutions to recurring flood risks.
