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. (150 words)

Causes

• Hydrological: probable maximum floods, extreme rainfall, overtopping and inadequate spillway capacity.
• Geotechnical and structural: weak foundation, seepage, piping, slope failure, ageing concrete and poor maintenance.
• Operational and human: flawed design, encroachment in reservoirs, sedimentation, delayed warnings, unsafe construction and cascading failures.
• Earthquakes, landslides and climate-driven extremes can compound these risks.

Examples

• Machhu-II dam failure, Gujarat (1979), caused a devastating downstream flood and heavy loss of life.
• Banqiao dam failure, China (1975), triggered by exceptional rainfall and cascading failures, caused catastrophic casualties.

Risk reduction

Independent safety reviews, instrumentation, emergency action plans, reservoir rule curves, catchment management, downstream zoning and community drills are necessary under a lifecycle approach.

Keywords

overtopping; piping; spillway; emergency action plan; cascading failure