9 hrs ago
Why Bihar Flooded Despite Poor Rains and Nepal’s Limited Role
Bihar had less rain than usual for most of the monsoon.
Even so, its rivers rose to very high levels and caused widespread flooding.
The Ganga was the first major river to become a serious concern this time.
Rain farther upstream, including around Uttar Pradesh, sent more water into the Ganga.
When the Ganga became swollen, smaller rivers found it harder to empty into it.
Nepal also experienced severe flooding after a glacial lake outburst, but the Gandak’s discharge into Bihar later fell.
Heavy local rain in parts of Bihar and Jharkhand added to the problem.
Embankments helped protect some areas, but seepage, drainage problems and overtopping still caused flooding.
Bihar’s flat land, heavy sediment and large population near rivers make it especially vulnerable.
Bihar received 27% less than normal rainfall between June 1 and September 8, yet major rivers rose sharply.
The Ganga exceeded previous highest flood levels at Patna’s Gandhi Ghat and Bhagalpur’s Sultanganj.
By September 9, flooding had affected about 40.51 lakh people across 14 districts.
Officials attributed the unusual flooding mainly to the Ganga’s high levels, upstream rainfall and backwater effects on tributaries.
Nepal’s glacial lake outburst contributed to flooding concerns, but Gandak discharge from the Valmikinagar Barrage later declined.
- Who
- Residents of Bihar were affected, while state officials including Vijay Kumar Choudhary and Santosh Kumar Mall explained the flooding.
- What
- Bihar experienced severe river flooding despite a cumulative rainfall deficit, with the Ganga exceeding previous highest flood levels at two locations.
- Where
- Flooding affected 14 districts of Bihar, including areas along the Ganga, Gandak, Kosi, Bagmati, Burhi Gandak, Punpun and Ghaghra rivers.
- When
- The flooding intensified in late August and early September; official impact figures were reported by September 9.
- Why
- High Ganga levels, upstream rainfall and river discharge, localised heavy rain, backwater effects and Bihar’s flat, sediment-heavy terrain contributed to the flooding.
Nepal and Farakka Concerns
Ganga and Upstream Factors
Main cause of the flooding
Nepal and Farakka Concerns
The August 26 glacial lake outburst in Tibet caused severe flooding in Nepal, and state leaders also contend that the Farakka Barrage has increased silt accumulation and worsened flooding in Bihar.
Ganga and Upstream Factors
Officials said the Gandak’s discharge after the Nepal event was lower than expected and declined, while the Ganga’s high level, upstream rainfall and discharge were more important immediate factors.
Role of the river system
Nepal and Farakka Concerns
Flooding in tributaries connected to Nepal and the Himalayan catchments remains a major concern because rivers such as the Kosi, Bagmati and Gandak enter Bihar from the north.
Ganga and Upstream Factors
The Ganga rose first in this episode and created a backwater effect, making it harder for the Gandak, Punpun and other rivers to drain.
Key facts
- Rainfall deficit
- Bihar received 601.1 mm of rain from June 1 to September 8, 27% below normal.
- September rainfall
- Rainfall during September was 31% above normal.
- Ganga at Patna
- The river reached 50.58 metres at Gandhi Ghat, six centimetres above the previous highest flood level recorded in 2016.
- Ganga at Bhagalpur
- The river reached 36.80 metres at Sultanganj, five centimetres above its previous highest flood level set in 2021.
- Flood impact
- By September 9, about 40.51 lakh people in 84 circles, 518 panchayats and 2,157 villages had been affected.
- Gandak discharge
- Discharge at the Valmikinagar Barrage reached 1,50,200 cusecs on August 26 before declining.
- Embankments
- Bihar has more than 3,730 kilometres of river embankments, and officials said no major modern scientific embankment suffered a large breach.
Quotes
Vijay Kumar Choudhary
Bihar Deputy Chief Minister and Water Resources Minister
“rainfall around the Allahabad and Varanasi region, and the resulting downstream discharge, were important factors behind the Ganga’s rise. For other rivers too, discharge from neighbouring states was a major factor.”
indianexpress.com
“Normally, the rivers entering Bihar from Nepal — the Bagmati, Kamla, Kosi and Gandak — rise first, followed by the Ganga. This time, the Ganga became the main source of concern first.”
indianexpress.com
Sources
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