Dam Failures in the U.S.

Dam failures1 in the U.S. are a somewhat frequent occurrence in the U.S. Over the period-of-record there have been an average of nearly 10 failures a year, considering dams of all sizes. Many failures are of small dams, that result in limited flooding and as a result have limited downstream impact. Download a report summarizing the dam failures in the U.S. here.

Go here for a description of the life-safety consequences of dam failures in the U.S.

Dam Failure Database Summary
The following table provides a summary of the NPDP dataset on dam failures in the U.S.

Period of Record
Number of Dam Failures
 - All Dams
 - Height < 15 meters
 - Height ≥ 15 meters
Number of States Having Dam Failures
State with the Most Failures
States with the Fewest Failures
Earliest Known Dam Failure

Timeline of Dam Failure Events
The figure below shows a timeline of dam failures in the U.S.

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Age of Dams at Failure
Failures can occur during any stage of a dam’s operation life; during first filling of the reservoir or decades later after years of satisfactory service. The following figure shows the distribution of the age of dams at the time of failure. There is an early mortality that is observed for dams; approximately 12% of failures occur during initial reservoir filling or during the first 10 years of operation. Over 10% of dam failures occur when dams are 100 years or older.

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Life-Safety Consequences of Dam Failures
Less than 4 percent of dam failures result in flooding that causes fatalities. However, dam failures have caused some of the largest disasters associated with the failure of man-made systems in the U.S. The failure of South Fork Dam in 1889 caused 2,209 fatalities in Johnstown, Pennsylvania and 450 lives were lost because of the St. Francis Dam failure in California in 1928. < href="http://npdp.stanford.edu/consequences_fatalities" target="_blank">Go here for more information on life-safety consequences of dam failures in the U.S.

1Dam Failure – Events that result in the uncontrolled release of the reservoir (URR). An incident that involves damage to a dam but retains control of the reservoir is not considered a dam failure.