Context
Recently, Bihar witnessed severe flooding despite receiving about 27% below-normal monsoon rainfall up to September 8. The floods were driven largely by high flows in the Ganga and its tributaries, upstream rainfall in India, localised heavy rain, siltation and drainage constraints, rather than unusually high releases from Nepal.
Explanation
- Bihar lies in the Ganga alluvial plain and is naturally flood-prone due to its flat terrain, low gradient and sediment-laden rivers.
- Major rivers include the Ganga, Kosi, Gandak, Bagmati, Kamla, Burhi Gandak, Ghaghra, Sone and Punpun.
- Rainfall in the wider river catchment, rather than Bihar’s average rainfall alone, determines river discharge; thus a rainfall deficit does not prevent floods.
- Heavy upstream rainfall and simultaneous swelling of tributaries can create a compound/junction flood in the Ganga system.
- When the Ganga is already swollen, tributaries such as the Gandak and Punpun face a backwater effect, slowing their drainage.
- Siltation raises riverbeds, while embankments can restrict natural floodplain drainage and contribute to waterlogging.
- Hence, Bihar’s floods reflect basin-wide hydrology, not merely local rainfall or Nepal-origin rivers.
La Excellence IAS Academy, the best IAS coaching in Hyderabad, known for delivering quality content and conceptual clarity for UPSC 2026 preparation.
FOLLOW US ON:
◉ YouTube : https://www.youtube.com/@CivilsPrepTeam
◉ Facebook: https://www.facebook.com/LaExcellenceIAS
◉ Instagram: https://www.instagram.com/laexcellenceiasacademy/
GET IN TOUCH:
Contact us at info@laex.in, https://laex.in/contact-us/
or Call us @ +91 9052 29 2929, +91 9052 99 2929, +91 9154 24 2140
OUR BRANCHES:
Head Office: H No: 1-10-225A, Beside AEVA Fertility Center, Ashok Nagar Extension, VV Giri Nagar, Ashok Nagar, Hyderabad, 500020
Madhapur: Flat no: 301, survey no 58-60, Guttala begumpet Madhapur metro pillar: 1524, Rangareddy Hyderabad, Telangana 500081
Bangalore: Plot No: 99, 2nd floor, 80 Feet Road, Beside Poorvika Mobiles, Chandra Layout, Attiguppe, Near Vijaya Nagara, Bengaluru, 560040
Bihar Floods Despite Rainfall Deficit