HOW THE RIVER KOSI’S SHIFTING COURSE EXPOSES THE PERILS OF EMBANKMENTS
HOW THE RIVER KOSI’S SHIFTING COURSE EXPOSES THE PERILS OF EMBANKMENTS
Introduction
The Kosi—often called “the river of sorrow”—is one of the most dynamic, sediment-laden rivers of the eastern Gangetic plains. Its catastrophic floods, such as the 2008 breach at Kusaha that displaced over 33 lakh people, reveal the deeper structural problem: embankments meant to protect communities are often the very systems that increase long-term vulnerability. As the Kosi continues to shift its course, the limitations of rigid flood-control engineering come into sharper focus.
The Kosi: A Geomorphologically Dynamic River
Natural Behaviour
Originates in Tibet and Nepal; joins Ganga in Bihar
Called Sapta Kosi because of its seven tributaries
Carries enormous sediment from the young Himalayas
Known to shift its course by tens of kilometres
Historical Shifts
The People’s Commission on Kosi Basin notes that the river has moved 120 km westwards in 250 years—a completely natural response to changing sediment load and slope.
Attempts to confine such a river within narrow human-made walls ignore its ecological realities.
Embankments: Promise and Paradox
Engineering Rationale
Embankments—earthen, stone or concrete walls—are designed to confine rivers, prevent seasonal overflows and protect agriculture and settlements.
Warnings Ignored
The G.R. Garg Committee (1951) warned that embankments disrupt two essential functions of any river:
Land formation through erosion and deposition
Drainage of the basin
The committee cautioned that embankments work only where rivers carry little silt—something the Kosi does not.
Counterproductive Consequences
Heavy silt deposition raises the riverbed higher than the surrounding land.
The embanked river becomes a “raised water channel”, increasing the risk of breaches.
When breaches occur, the flood intensity is far greater than natural floods.
Repeated Failures: Lessons from the Kosi
The Kosi has breached embankments repeatedly—1963, 1968, 1971, 1980, 1984, 1987, 1991, 2008 and 2024.
Each breach displaces lakhs and devastates farmland.
Mechanisms of Failure
Increased silt load, especially during monsoon
Backflow and pressure at barrages
Narrowing of river channel by embankments
Water-logging for communities trapped between embankments
Voices from the Ground
Local movements such as the Kosi Nav Nirman Manch highlight how embankments trap people inside, block evacuation routes, and provide no long-term rehabilitation.
Region-Specific Approaches: East vs. West Himalaya
Experts differentiate between:
Influents (western rivers): declining precipitation downstream → more stable, less flood-prone
Affluents (eastern rivers): rising rainfall downstream → unpredictable, shifting, sediment-heavy
Thus, embankments may be suitable in the west but dangerous in the east, where geology is weak and landslides frequent.
Alternatives: Learning to Live With Floods
Global Example
The U.S. has dismantled many embankments, allowing rivers to spread naturally and reducing extreme flooding.
Indian Alternatives
Restore paleochannels so water spreads safely
Scientific desiltation
Early warning systems and local training
Rehabilitation outside embankment zones
Adopt flood-resistance, not flood-control, as the policy goal
Allow seasonal flooding to recharge groundwater and support ecosystems
Why These Work
Natural floods are widespread but milder; embanked floods are sudden and devastating. Letting the river function as a drainage system reduces long-term vulnerability.
Political Economy and the Embankment Dilemma
Even as evidence mounts against embankments, political incentives remain strong:
Election promises such as Bihar’s “flood to fortune” river-linking model assume embankments will enable irrigation and fisheries.
But diverting water through canals cannot offset the 6 lakh cusecs that the Kosi brings during peak floods.
Continuous spending on raising embankments becomes financially unsustainable and ecologically damaging.
Conclusion
The Kosi’s persistent flooding is not merely a natural disaster but a policy-induced vulnerability. Embankments designed to control the river have instead amplified the risks by constraining a dynamic, silt-rich river. A paradigm shift—from flood-control to flood-resilience—is urgently needed. The Kosi insists on one truth: rivers cannot be permanently tamed; they must be understood and accommodated.
MAINS QUESTIONS
- Examine how geomorphological characteristics of Himalayan rivers influence their flood behaviour with reference to the Kosi.
- Critically analyse the role of embankments in flood management in India. Are they a solution or a problem? Discuss with examples.
