Natural Dam Threat Massive Landslide Blocks Siji River in Arunachal, Sparking Flash Flood Emergency for Downstream Assam

A highly critical situation has unfolded along the Assam-Arunachal Pradesh border after a massive, rain-triggered landslide blocked the Siji River at the Siji-Magi Block Point in Arunachal’s Lower Siang district. The immense debris flow has natural-dammed the river, creating a rapidly expanding artificial lake just a few miles upstream from Likabali town. District authorities from both states have issued emergency warnings, stating that the natural blockage is under intense structural pressure from water accumulation. If the debris dam suddenly breaks, a catastrophic, powerful flash flood could surge down the river valley without warning, threatening lives, homes, livestock, and vital public infrastructure. Residents along the riverbanks—where the Siji flows into Assam and becomes the Gai River—have been advised to prepare for immediate evacuation to safer locations at short notice.

The downstream impact of this monsoon fury is already heavily battering Assam’s adjoining Dhemaji district, where overflowing waters have inundated 69 villages across four revenue circles—Jonai, Sissiborgaon, Dhemaji, and Gogamukh—affecting over 15,483 people. The sheer velocity of the current has caused widespread structural damage, collapsing a key railway bridge across the Simen River, washing away an iron bridge, and triggering severe embankment erosion along arterial stretches of National Highway 52. Concurrently, rescue teams are continuing their search in Arunachal’s Keyi Panyor district following a separate, devastating flash flood at a hydropower colony on June 24 that left several missing. Amidst the crisis, the Border Roads Organisation (BRO) managed a major breakthrough by working round-the-clock to restore the landslide-buried Kimin-Potin Road within 36 hours, reopening a critical lifeline for five isolated, higher-elevation districts.