Bihar Floods Defy Drought: How Rivers Swelled?

Bihar, initially facing drought-like conditions with a 27% rainfall deficit until September 8, experienced severe floods as river levels rose sharply. The Ganga notably surpassed its highest flood levels in Patna and Bhagalpur, impacting 14 districts and affecting approximately 40.51 lakh people by September 9.

This year's flood pattern differed, with the Ganga rising before rivers typically originating from Nepal. Increased discharge from Uttar Pradesh and rainfall around Allahabad and Varanasi were significant factors in the Ganga's surge. Localized heavy rainfall in Bihar during the worsening flood situation also contributed.

A glacial lake outburst in Tibet on August 26 caused flooding in Nepal, leading Bihar to open all 36 gates of the Valmikinagar Barrage on the Gandak. Despite initial lower-than-expected discharge, the Ganga's high levels created a backwater effect, hindering drainage for tributaries like the Gandak and Punpun, which was also affected by Jharkhand's rainfall.

The extensive river network, including the Kosi, Gandak, and Bagmati, exacerbated the flooding across Bihar's flat plains. Many of these rivers were reported above danger levels at various points, with the Ganga itself breaching mark at multiple locations.

While Bihar's 3,730 km of embankments protected large areas, flooding occurred through seepage and localized issues. Sediment accumulation within river channels is identified as a permanent vulnerability, potentially worsened by downstream conditions near the Farakka Barrage.

Concerns are also rising over the Farakka Barrage's role in silt accumulation, potentially making the Ganga shallower and prone to overflow. As the 1996 India-Bangladesh Farakka Treaty approaches its December 2026 expiration, calls to review or scrap it are intensifying. Bihar's geography, with shifting riverine islands and high population density near rivers, further adds to the flood risk.