---
title: "Kosi River: Sorrow of Bihar Explained | Model Diplomat"
description: "The Kosi River, known as the \"Sorrow of Bihar,\" is a major Himalayan river famous for its catastrophic floods and shifting course, impacting local communities."
url: "https://modeldiplomat.com/learn/glossary/kosi-river"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- The Kosi is a major trans-boundary Himalayan river that rises in Tibet and Nepal and joins the Ganga in Bihar, notorious for catastrophic course-shifting floods.
- Why is the Kosi called the 'Sorrow of Bihar'?
- What is the Kosi Treaty of 1954?
- What are the seven tributaries of the Sapta Kosi?
- How does the Kosi differ from the Damodar's 'Sorrow of Bengal' label?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

The Kosi is a major trans-boundary Himalayan river that rises in Tibet and Nepal and joins the Ganga in Bihar, notorious for catastrophic course-shifting floods.

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In August 2008 the Kosi breached its eastern embankment at Kusaha in Nepal's Sunsari district, avulsing into an abandoned channel and displacing roughly three million people across the Bihar districts of Supaul, Madhepura and Araria.

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