Dam Failures and Incidents

Dam Failures and Incidents

Hundreds of dam failures have occurred throughout U.S. history. These failures have caused immense property and environmental damages and have taken thousands of lives. As the nation’s dams age and population increases, the potential for deadly dam failures grows.

No one knows precisely how many dam failures have occurred in the U.S., but they have been documented in every state. From Jan. 1, 2005 through June 2013, state dam safety programs reported 173 dam failures and 587 "incidents" - episodes that, without intervention, would likely have resulted in dam failure.

The map below is based on a (non-comprehensive) list of dam and levee failures compiled by ASDSO. The map demonstrates that dam failures are not particularly common but they do continue to occur. Locations are approximate.

The large red dot on the Gulf Coast represents the New Orleans levee failures resulting from Hurricane Katrina. A few other levee failures are included such as all of those indicated in Northern California. If levee failures from the 1993 floods were included, more failures would be indicated in the center of the map.

Map courtesy of James S. Halgren, Office of Hydrologic Development, National Weather Service, National Oceanic and Atmospheric Administration


Learning from the Past: A Snapshot of Historic U.S. Dam Failures

At 7:20 a.m. on May 16, 1874, the 43-foot-high Mill River Dam above Williamsburg, Massachusetts failed, killing 138 people, including 43 children under the age of ten. This failure was the worst in U.S. history, up to that time.

Fifteen years later, on May 31, 1889, this tragedy was replayed on a larger scale in Pennsylvania. Over 2,200 people - more than one in five residents of Johnstown - perished in the flood caused by the failure of South Fork Dam, nine miles upstream.

Many more failures - in Arizona, Tennessee, Oregon, North Carolina, Texas, Virginia, West Virginia, and elsewhere across the U.S. - occurred around the turn of the century, and some early state dam safety legislation was passed.

The failure of St. Francis Dam, in March 1928, was a landmark event in the history of state dam safety legislation, spurring legislation not only in California, but in neighboring states as well. However, most states had no substantive dam safety laws prior to a series of dam failures and incidents that occurred in the 1970s:

February 26, 1972 - Buffalo Creek Valley, West Virginia
The failure of a coal-waste impoundment at the valley’s head took 125 lives, and caused more than $400 million in damages, including destruction of over 500 homes.

June 9, 1972 – Rapid City, South Dakota
The Canyon Lake Dam failure took an undetermined number of lives (estimates range from 33 to 237). Damages, including destruction of 1,335 homes, totaled more than $60 million.

June 5, 1976 – Teton, Idaho
Eleven people perished when Teton Dam failed. The failure caused an unprecedented amount of property damage totaling more than $1 billion.

July 19-20, 1977 – Laurel Run, Pennsylvania
Laurel Run Dam failed, killing over 40 people and causing $5.3 million in damages.

November 5, 1977 – Toccoa Falls, Georgia
Kelly Barnes Dam failed, killing 39 students and college staff and causing about $2.5 million in damages.

Following the Toccoa Falls tragedy, President Jimmy Carter directed the US Army Corps of Engineers to inspect the nation’s non-federal high-hazard dams. This “Phase I Inspection Program” lasted from 1978-1981.

The findings of the inspection program were responsible for the establishment of dam safety programs in most states, and, ultimately, the creation of the National Dam Safety Program, which supports dam safety programs in 49 states – all but Alabama, which has yet to pass dam safety legislation.


Marking Significant Dam Failures

The ASDSO Dam Failures & Incidents Committee (DFIC) has a mission to assist the states to improve the practice of investigating/learning from dam failures and incidents (learn more at the DFIC Page). The committee has a goal to “collect and share lessons learned from past dam failures/incidents with the ASDSO membership” and has initiated a project to highlight and share information on the “Decade Anniversary” of significant dam failures.


March 12 – 10th Anniversary of the Big Bay Dam Failure, Mississippi

May 16 – 140th Anniversary of the Mill River Dam Failure, Massachusetts

May 25 – 100th Anniversary of the Hatchtown Dam Failure, Utah

May 31 – 125th Anniversary of the South Fork Dam Failure (Johnstown Flood), Pennsylvania

June 10 – 50th Anniversary of the Swift and Lower Two Medicine Dam Failures, Montana

December 23 – 50th Anniversary of the Hell Hole Dam Failure, California


March 6 - 50th Anniversary of the Norwich Flood

May 7 - 10th Anniversary of the Silver Lake Dam Failure

December 6 - 50th Anniversary of the Baldwin Hills Dam Failure


Other Links to Selected Dam Failures, by Location

West Virginia


Causes of Dam Failures


Overtopping of a dam, as shown above, is often a precursor of dam failure. National statistics show that overtopping due to inadequate spillway design, debris blockage of spillways, or settlement of the dam crest account for approximately 34% of all U.S. dam failures.

Animation of an overtopping failure
Animation of an overtopping failure (requires Flash Player)

(Windows Media format)

Other Causes

Other causes of dam failures include structural failure of the materials used in dam construction and inadequate maintenance.

Source: National Performance of Dams Program

Foundation Defects and Slope Instability

Foundation defects, including settlement and slope instability, cause about 30% of all dam failures.

Animation of a slide failure
Animation of a slide failure (requires Flash Player)

(Windows Media format)


Another 20% of U.S. dam failures have been caused by piping (internal erosion caused by seepage). Seepage often occurs around hydraulic structures, such as pipes and spillways; through animal burrows; around roots of woody vegetation; and through cracks in dams, dam appurtenances, and dam foundations.

Animation of a piping failure
Animation of a piping failure (requires Flash Player)

(Windows Media format)


Web Resources - General

ASDSO Computer Animations of failure modes: Overtopping - Piping

ASDSO maintains a list of dam failures and incidents dating from from 1869 to present. This listing is a work in progress; please contact info@damsafety.org to supply additional information.

Photographs and descriptions of dam failures are posted in the ASDSO Picture Gallery, located in the Publications and Resources section of the website. (Choose "Dam Failures & Incidents" in the Category drop-down box.)

The ASDSO Dam Failures and Incidents Committee developed a Dam Failure Investigation Guideline for states and other entities to use in the event of a dam failure.

FEMA: Dam Failure - Before, During, & After. Dam failure information from the National Dam Safety Program.

National Performance of Dams Program. The NPDP, based at Stanford University maintains a database of dam failures and their causes.

Cracking Dams. This educational site features computer simulations and case studies.

Tailings Dam Failures. A list of failures of dams that impound mine wastes, maintained by the World Information Service on Energy (WISE).

Association of State Dam Safety Officials, 450 Old Vine St., Lexington, KY 40507 | 859/550-2788 | info@damsafety.org

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