Rescue or relief come first. But Kerala's forgotten flood defence may lie under waters

For those of us from Thiruvananthapuram, Aruvikkara Dam is a cherished childhood memory. Nearly fifty years ago it was a favourite picnic spot—a vast expanse of water with large fish swimming freely in the reservoir, as fishing was prohibited and visitors fed them. A well-kept garden and an ancient Durga Devi temple added to its charm. Citizens also visited because the reservoir was, and remains, the source of clean drinking water for the city.

The dam also supports irrigation in nearby areas such as Peyad, Irumpa and Perukavu. Larger dams serving irrigation, drinking water and hydropower dominated the news last week as Kerala witnessed yet another spell of devastating floods. The flood threat has not receded even as we upload this article.

Kerala has 54 large dams, nearly 40 of them used for hydropower and the rest mainly for irrigation and drinking water. Most are between 30 and over 80 years old. Decades of silt accumulation have inevitably reduced their live storage. The recent desilting of the Aruvikkara reservoir showed that its effective storage had fallen to less than half its original capacity after nearly ninety years. Even while the work continues, the additional storage created has already reduced the vulnerability of the Karamana River to flash floods.

Exceptionally heavy rainfall, including nearly 39 cm recorded at Vadasserikkara in Pathanamthitta district, triggered landslips, inundated houses, stranded people and cut off access to thousands. As I write this, lives have been lost, homes damaged and thousands shifted to relief camps. The images brought back painful memories of the floods of 2018 and 2019.

The economic loss is enormous. Crops have been destroyed, buildings damaged, shops in small towns have lost their stocks and thousands of livelihoods have been disrupted. Unfortunately, such rain-induced devastation has become almost routine in Kerala. The resilience of our people remains admirable, but our long-term preparedness has not kept pace with the recurring challenge.

Among the many causes of flooding, one stands out. Reservoirs fill rapidly, dams are forced to release water and rivers overflow within hours. In a State with a population density of nearly 950 persons per square kilometre, the consequences are severe because rivers, reservoirs and human settlements exist in extremely close proximity. For context, the density of population in Tamil Nadu is 550 and Karnataka, 350.

This brings us to one of Kerala's most neglected flood-mitigation measures—systematic desilting of reservoirs and dredging of rivers. Much of this work has remained pending for decades, reducing both storage capacity and the carrying capacity of rivers. While this is a national problem, Kerala's vulnerability is far greater because of its unique geography and dense settlement pattern.

The recent experience at Aruvikkara demonstrates that this need not become an unaffordable exercise. The initial estimate of around ₹75 crore was reportedly brought down to about ₹14 crore by designing the contract to permit the successful bidder to utilise the excavated sand. The arrangement reduced the burden on the public exchequer while ensuring that the removed material found productive use. Large-scale desilting can similarly generate local employment, stimulate business activity around project sites and partly offset income losses caused by floods.

A study published in December 2025 by the Indian Institute of Science Education and Research (IISER), Bhopal, examined more than 300 large reservoirs across India and confirmed that heavy silt accumulation has significantly reduced their storage capacity, affecting flood moderation, irrigation and hydropower generation. Even where only 10 to 15 per cent of capacity has been lost, timely desilting can make a meaningful difference.

The obvious question is: where will the funds come from? The Centre's Scheme for Special Assistance to States for Capital Investment (SASCI) presently supports creation of capital assets.

There is a case for treating desilting/dredging under capex restoration efforts.Restoring the original storage capacity of reservoirs enhances dam safety, strengthens irrigation, improves flood moderation and increases hydropower generation. It is, in effect, restoration of a valuable public asset. In effect, incremental capacity is being “created”. Where river dredging is integrated with inland water transport for goods or commodities or other productive uses, the case becomes even stronger.

Desilting reservoirs and dredging rivers should therefore be viewed not as an expense but as an investment in water security, irrigation and clean energy. Preservation of infrastructure deserves as much importance as creating new infrastructure.

If States prepare well-documented Detailed Project Reports demonstrating these long-term public benefits under infrastructure works, the Union Government’s screening committee under the 50-year interest-free capex loans scheme should seriously consider extending capital support. An allocation of even ₹750-1,000 crore initially under such a programme could substantially restore the utility of Kerala's reservoirs and rivers and strengthen the State's first line of defence against floods.