Dam failures are always catastrophic, especially on the downstream side, resulting in a colossal loss of life and property. Analyze the various causes of dam failures. Give two examples of large dam failures.

Introduction

A dam failure releases an uncontrolled flood downstream, causing catastrophic loss of life and property; India, with over 6,000 large dams, many ageing, is especially exposed.

Causes of dam failure

• Overtopping: inadequate spillway capacity during extreme floods lets water flow over the crest — the single most common cause.
• Foundation failure: weak or permeable foundations that settle or slide.
• Piping/internal erosion: seepage carrying soil out of the embankment, hollowing it from within.
• Structural and design defects and use of poor construction material.
• Poor maintenance and monitoring, and sedimentation reducing storage.
• Natural triggers: earthquakes and landslides into the reservoir (as glacial-lake outbursts threaten Himalayan dams).

Two examples of large dam failures

• Machchhu-II dam, Morbi, Gujarat (1979): overtopping during heavy floods breached the dam, killing thousands — among the worst dam disasters.
• Banqiao Dam, China (1975): extreme rainfall combined with inadequate spillway capacity caused a catastrophic failure with massive casualties, a textbook case of overtopping.

Conclusion

With many Indian dams over 50 years old, the Dam Safety Act, 2021 — mandating regular inspection, risk classification and Emergency Action Plans — and continuous instrumentation-based monitoring are vital correctives to prevent such downstream catastrophes.