Context:
The Kosi River, infamously known as the “River of Sorrow”, continues to demonstrate the limits of structural flood control measures in the Gangetic plains. Recurrent embankment breaches, most notably the 2008 Kusaha breach in Nepal, reveal how engineering interventions have failed to account for the river’s dynamic geomorphology, heavy silt load, and natural tendency to shift course.
Key Highlights:
Nature and Behaviour of the Kosi River
- Originates in Tibet, flows through Nepal, and enters Bihar before joining the Ganga.
- One of the most silt-laden rivers in the world due to erosion in the Himalayan catchment.
- Has shifted nearly 120 km westward in the last 250 years, indicating high river mobility.
2008 Embankment Breach and Its Impact
- August 2008: Embankment breach at Kusaha (Nepal).
- Affected nearly 33 lakh people in Bihar.
- Caused over 400 deaths, mass displacement, and loss of livelihoods.
- Floodwaters flowed along old paleochannels, exposing weaknesses in embankment-based control.
Role of Barrages and Embankments
- Kosi Barrage (1950s) and subsequent embankments altered the river’s natural sediment dispersal.
- G.R. Garg Committee (1951) warned that embankments are ineffective for high-silt rivers.
- Continuous silt deposition raises the riverbed above surrounding land, increasing breach risk.
- Multiple embankment failures recorded since 1963.
Policy and Political Dimensions
- NDA’s “flood to fortune” promise includes river-linking projects like Kosi–Mechi.
- Experts argue such projects may aid irrigation, but are unlikely to handle peak monsoon discharges.
Relevant Prelims Points:
- Issue & Causes:
- Heavy siltation, dynamic river course, rigid embankment structures.
- Government Interventions:
- Barrages, embankments, river-linking proposals.
- Benefits of Embankments:
- Short-term flood protection for settlements and agriculture.
- Challenges:
- Raised riverbeds, catastrophic breaches, waterlogging, ecological damage.
- Impact:
- Increased long-term flood vulnerability and disaster risk.
Relevant Mains Points:
- Key Concepts & Definitions:
- Embankments: Artificial barriers to confine river flow.
- Siltation: Deposition of sediments reducing channel capacity.
- Paleochannels: Ancient river paths that can redistribute floodwaters.
- Environmental and Ecological Concerns:
- Disruption of groundwater recharge, wetland ecosystems, and biodiversity.
- Disaster Management Perspective:
- Structural measures alone are inadequate for Himalayan rivers.
- Way Forward:
- Shift towards “living with floods” approach.
- Strengthen early warning systems and floodplain zoning.
- Rehabilitation outside embankments.
- Scientific desilting, revival of paleochannels, and basin-level river management.
- Integrate ecological engineering with disaster resilience planning.
UPSC Relevance (GS-wise):
- GS 1: Indian Geography – River systems, fluvial processes, floodplains.
- GS 3: Disaster Management – Flood mitigation strategies.
- GS 3: Environment & Ecology – River ecology, sustainable interventions.