The Geological Survey of India (GSI) issued a critical orange-level landslide warning for Darjeeling at 2:15 PM, mere hours before torrential rainfall unleashed widespread landslides across the region. Dr. Saibal Ghosh, GSI Deputy Director General and landslide expert, attributed the disaster to intense downpours that destabilized the already waterlogged Himalayan slopes.

The GSI’s operational bulletin, disseminated via the 'Bhusanket' portal and 'Bhooskhalan' app, targeted Darjeeling Pulbazar, Jorebunglow Sukiapokhri, Kurseong, Mirik, and Rangli Rangliot blocks. Dr. Ghosh explained that daily landslide forecasts are publicly available for Darjeeling, Kalimpong, Nilgiris (Tamil Nadu), and Rudraprayag (Uttarakhand), while 17 other districts in eight states receive bulletins for validation. These forecasts integrate real-time India Meteorological Department (IMD) rainfall data with GSI’s geological assessments, which flagged the region’s saturated slopes as highly vulnerable.

With over 30 years of Himalayan research, Dr. Ghosh noted that October rainfall is particularly hazardous. “The monsoon from June to October saturates the soil, but October’s heavy rains are especially risky,” he said. Kurseong recorded 393 mm of rainfall on October 4–5, 2025, surpassing the 130–150 mm daily threshold for triggering landslides. “If the rain had continued past October 5, the destruction could have been far worse,” he added.

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Historical records reveal October’s recurring threat in the Darjeeling-Sikkim Himalayas. Dr. Ghosh cited the 1968 catastrophe, when 1,121 mm of rainfall, including 499 mm in one day, caused floods, landslides, and 677 fatalities, burying major roads like NH10 for over a year. Similar events struck in 1978, 1979, 1981, 1993, 1998, 2001, 2006, 2007, 2015, and 2023, underscoring the region’s fragility.

Dr. Ghosh explained that landslides result from gravitational processes, exacerbated by geological instability and external triggers like rainfall or human activity. Darjeeling’s steep slopes and fractured rocks, part of the geologically young Himalayas, are naturally prone to collapse. “Weak rock formations are often just waiting for a trigger like heavy rain,” he said.

Human activities, such as building homes across drainage channels, further aggravate risks by obstructing natural water flow. “Unregulated construction on unstable slopes invites disaster,” Dr. Ghosh warned, advocating for stringent state regulations.

The GSI’s proactive warnings and monitoring highlight the need for robust forecasting, public awareness, and regulatory enforcement to protect lives in this volatile region.

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