At a Glance
Four facts to hold on to.
Machchhu II, 1979
Overtopping; Morbi hit; toll uncertain.
Panshet, 1961
Piping; Khadakwasla then overtopped.
Dam Safety Act, 2021
National committee and authority; owner duties.
Exam angle
Analyse causes; use two examples.
In this lesson
What Fails, and Why
Hazard and risk
- A breach is a gap through a dam. Stored water may rush out.
- Hazard is the possible flood and its force.
- Risk also asks who stands in its path.
- A small flood near many homes can carry serious risk.
Four failure paths
| Path | What happens |
|---|---|
| Heavy inflow | Extreme rain fills the reservoir faster than the spillway can pass water |
| Internal erosion (piping) | Water finds a path through earth or foundation; muddy seepage is a warning |
| Structural damage | Concrete, gates or foundations crack or move |
| Operating failure | Faulty gates, missing data or late decisions worsen a flood |
- Overtopping can erode an earth dam.
- Piping can grow into a hidden channel until the dam fails.
- A spillway is the route built to release surplus water.
- A warning sign is not the same as a breach.
- No article can predict warning time from dam type alone.
- Sources: CWC flood-risk mapping guide; Dam Safety Act, 2021 (indiacode.nic.in).
True or False: A dam breach can send a flood wave downstream quickly, so warning and evacuation plans matter.
True or False: Seepage that carries soil out of an earthen dam is harmless and needs no inspection.
Two Indian Failures
Machchhu II, Gujarat, 1979
- On 11 August 1979, intense monsoon rain drove a huge flood into Machchhu II.
- Water overtopped both earthen sides of the central spillway. The earth sections washed away.
- A fast flood struck Morbi and nearby villages.
- The death toll is uncertain. The US Bureau of Reclamation reported more than 1,300 deaths in Morbi and warned wider totals are hard to establish.
- Storms and broken communication limited warning.
- Reports differ on how unusual the inflow was. Do not treat one design ratio as the whole cause.
Panshet and Khadakwasla, Maharashtra, 1961
- Panshet breached on 12 July 1961, in its first year of storing water.
- The Central Water Commission lists piping as the failure mode.
- A JICA study also describes improper concrete work.
- The surge overtopped Khadakwasla downstream. Pune flooded.
- This is a cascade: trouble at one dam changes conditions at another.
- Exam distinction: Machchhu II failed by overtopping. Panshet failed by piping. Khadakwasla was overtopped.
- Sources: US Bureau of Reclamation; CWC list of reported failures; JICA Maharashtra dam study; 1963 Panshet–Khadakwasla inquiry record.
True or False: Panshet breached in 1961, and its flood surge then overtopped Khadakwasla downstream.
True or False: The Machchhu II and Panshet disasters happened in the same decade.
Preventing a Disaster
Who checks a dam?
- The Dam Safety Act, 2021 covers specified dams.
- It creates a National Committee on Dam Safety and a National Dam Safety Authority.
- State committees and State Dam Safety Organisations have state roles.
- The owner must operate, inspect and maintain each covered dam.
- Inspections are due before and after the monsoon, and after a flood, earthquake or sign of distress.
- Owners must prepare an emergency action plan for each covered dam. Do not assume every plan is complete.
- Source: Dam Safety Act, 2021, sections 31 and 35–36 (indiacode.nic.in).
Emergency action
- Monitor rain, water and seepage.
- Inspect and judge the danger.
- Alert district and downstream people.
- Evacuate and review the event.
- Inundation maps show areas that could flood. They are planning estimates.
- The Dam Rehabilitation and Improvement Project (DRIP) funds repairs and better monitoring at selected dams.
- A 2024 World Bank report described upgraded instruments and plans, and why nearby dams must share data.
- Sources: CWC emergency-plan guide; World Bank, DRIP, 2024.
Who does what?
| Action | What it limits | Who leads |
|---|---|---|
| Inspect and repair | Weak points before failure | Dam owner and safety unit |
| Review flood design | Spillway shortfall | Owner with experts |
| Share warnings | Time lost | Owner, district, disaster agencies |
| Practise evacuation | Blocked roads, weak alerts | District, local bodies, residents |
Lessons from abroad
- Banqiao in China failed in 1975 during extreme rain.
- Teton in the United States failed in 1976 after serious seepage.
- At Vajont in Italy, a landslide drove a wave over the dam in 1963. The dam itself did not collapse.
- Old dams face changing rain, sediment, ageing parts and more people downstream.
- Sources: US BoR, Teton; US BoR, Banqiao and Vajont.
Think it through: why is a large flood not proof that a dam broke?
A dam can release water safely or dangerously while its wall stays intact. Sudden releases, blocked gates or a wave over the crest can flood settlements. Check the event record before calling it a breach.
True or False: China’s Banqiao dam failed in 1975 during extreme rain.
True or False: Sediment build-up cannot reduce reservoir storage or complicate safe flood management.
Previous Year Questions
UPSC Mains 2023 asked about dam failures.
- UPSC Mains 2023, GS III, Q7Analyse the causes of dam failures and give two large examples. Build the answer around inflow, structure, operation and warnings. Use Machchhu II and Panshet to show different paths. End with inspection, flood review and emergency planning. View the question.
True or False: UPSC Mains 2023 expected analysed causes of dam failures, not just a description of what happened.
Quick Q&A
Machchhu II year?
1979.
Panshet mode?
Piping.
Overtopping?
Water flows over the crest.
Act year?
2021.
Mains Q7?
Causes and two examples.
🎲 Practice: Dam Failures in India
4 verified questions from this topic.
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