Recent devastating floods that ravaged Jorhat, Sivasagar, and Charaideo districts in Upper Assam were primarily triggered by extensive deforestation in the upper reaches of Nagaland, according to internationally acclaimed river expert Professor Nayan Sharma. The loss of vital forest cover, he explained, led to an accelerated overland flow of extreme rainstorm water, carrying massive amounts of silt that subsequently buried homes and significantly raised riverbed levels in the affected areas.
Professor Sharma highlighted that this catastrophic event was preceded by an enormous precipitation spell, measuring approximately 239 mm, which occurred between July 18 and 20 in Nagaland's Mon district. This heavy rainfall, combined with the denuded landscape, generated a "massive flood hydrograph" of very fast-flowing, silt-laden stormwater, overwhelming natural drainage systems.
According to estimates cited by Professor Sharma, who is a former Professor of IIT Roorkee, Nagaland witnessed the loss of around 800 square kilometres of forest cover between 2013 and 2023, a figure he suggests could be considerably higher now. This substantial reduction in stabilising vegetation has critically altered watershed hydrology, accelerating surface runoff and soil erosion by an estimated 1.5 to 2 times during intense rainfall events.
He further elaborated that in the presence of adequate vegetation cover, a significant portion of stormwater typically percolates into the subsoil groundwater, thereby considerably diminishing the volume of overland surface water flow. The absence of such natural absorption mechanisms due to deforestation has thus exacerbated flood severity, turning heavy rainfall into destructive torrents across downstream regions of Assam.
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