1. Johnstown Dam Disaster:

The Johnstown Flood (locally, the Great Flood of 1889) occurred on May 31, 1889, after the catastrophic failure of the South Fork Dam on the Little Conemaugh River 14 miles (23 km) upstream of the town of Johnstown, Pennsylvania, USA. The dam broke after several days of extremely heavy rainfall, unleashing 20 million tons of water (18 million cubic meters) from the reservoir known as Lake Conemaugh. With a flow rate that temporarily equalled that of the Mississippi River, the flood killed 2,209 people and caused US$17 million of damage (about $425 million in 2012 dollars). More details

2. St. Francis Dam Disaster:

The St. Francis Dam was a curved concrete gravity dam, built to create a large regulating and storage reservoir for the City of Los Angeles, California. At two and a half minutes before midnight on March 12, 1928, the dam catastrophically failed, and the resulting flood took the lives of as many as 600 people. The collapse of the St. Francis Dam is considered to be one of the worst American civil engineering disasters of the 20th century and remains the second-greatest loss of life in California's history, after the 1906 San Francisco Earthquake and fire. The disaster marked the end of Mulholland's career. More details

3. Canyon Lake Dam Disaster:

The Black Hills Flood of 1972, also known as the Rapid City Flood, was one of the most detrimental floods in the history of South Dakota. It took place on June 9–10, 1972 in the Black Hills of Western South Dakota. 15 inches (380 mm) of rainfall over six hours sent Rapid Creek and other waterways overflowing, flooding many residential and commercial properties in Rapid City. It also caused flooding of Battle, Spring, Bear Butte, and Boxelder Creeks. During the night of June 9, Canyon Lake Dam became clogged with debris and failed, resulting in 238 deaths and 3,057 injuries. Several bodies were never found. Over 1,335 homes and 5,000 automobiles were destroyed. The value of the damaged property was over US $160 million in 1972 dollars. More details

4. Mill River Dam Disaster:

The Mill River flood was the first major dam disaster in the United States and one of the greatest calamities of the nineteenth century.  It happened early one May morning in 1874, in the hills above the western Massachusetts towns of Williamsburg and Northampton, when a reservoir dam (used for waterpower) suddenly burst, sending an avalanche of water down a narrow valley lined with factories and farms.  Within an hour, 139 people were dead, and four mill villages were washed away.  The Mill River flood instantly became one of the nation’s big news stories. More details

5. Buffalo Creek Dam Disaster:

The Buffalo Creek flood was a disaster that occurred on February 26, 1972, when the Pittston Coal Company's coal slurry impoundment dam #3, located on a hillside in Logan County, West Virginia, burst, four days after having been declared 'satisfactory' by a federal mine inspector. The resulting flood unleashed approximately 132,000,000 US gallons (500,000 m3) of black waste water, cresting over 30 ft high, upon the residents of 16 coal towns along Buffalo Creek Hollow. Out of a population of 5,000 people, 125 were killed, 1,121 were injured, and over 4,000 were left homeless. 507 houses were destroyed, in addition to forty-four mobile homes and 30 businesses. More details

6. Walnut Grove Dam Disaster:

On February 22, 1890 the Walnut Grove Dam burst sending a wall of water 100 feet high down the Hassayampa River. By the time it reached Wickenburg, 60 miles downstream, it is said that the wall of water was still a whopping 40 feet high. If you have ever been to Wickenburg, its hard to imagine. Treasure hunters have been scouring the sands of the Hassayampa ever since, looking for safes, coins, and other caches bound to have been swept up by the torrent. From Wagoner all the way to the Gila River, you can still see evidence of this amazing flood. Read a little here and maybe find yourself a little treasure too. More details

7. Austin Dam Disaster:

Austin Dam was a dam in the Freeman Run Valley, Potter County, Pennsylvania, which serviced the Bayless Pulp & Paper Mill. On September 30, 1911, the dam failed and destroyed the Bayless Pulp & Paper Mill as well as much of the town of Austin. The damage was approximately $10 million. It also resulted in the deaths of 78 people. A young girl named Mary Fran Simmons, a new immigrant from Galicia which was part of the Austro-Hungarian Empire, warned many of the townspeople about the impending disaster with her extremely limited English, simply pointing and repeating, "Dam! Dam!" The paper mill and dam were subsequently rebuilt, but the mill was lost in a fire in 1933. The new dam failed in 1942 with no loss of life. The dam was not replaced after the second failure. More details 

8. Laurel Run Dam Disaster:

The Laurel Run Dam, also known as Laurel Run Dam No. 2, was an earthen embankment dam that failed during the 1977 Johnstown flood. It had the largest reservoir of seven dams to fail between July 19 and 20, 1977 and caused the most fatalities of the two that did. The dam failed in the early morning of July 20 after period of heavy rain, causing 101 million US gallons (380,000 m3) of water to flood downstream Tanneryville, killing 40 people. More details

9. Kelly Barnes Dam Disaster:

Kelly Barnes Dam was an earthen embankment dam once located in Stephens County, Georgia, just outside of the city of Toccoa. It collapsed on November 6, 1977 after a period of heavy rainfall, and the resulting flood killed 39 people and caused $2.8 million in damages. The dam was never rebuilt, and the Toccoa Falls downstream of the dam site is now a memorial and tourist attraction on the campus of Toccoa Falls College. More details

10. Lower Otay Dam Disaster:

Lower Otay Reservoir was originally created in 1897 after the construction of the Lower Otay Dam by the Southern California Mountain Water Company. The original dam was a rock fill type of 125 feet (38 m) high. That dam gave way in January 1916 following heavy rains which affected most of Southern California flooding the Otay Valley with a wall of water ranging from 20 to 100 feet (6.1 to 30.5 m) in height during the event, killing more than 14 people.[8] The flood swept away entire farms and buildings, including the Montgomery residence at Fruitland near the mouth of the river, where John J. Montgomery had built his initial series of manned glider designs. More details

11. Teton Dam Disaster:

The Teton Dam was an earthen dam on the Teton River in Idaho, United States. It was built by the Bureau of Reclamation, one of eight federal agencies authorized to construct dams. Located in the eastern part of the state, between Fremont and Madison counties, it suffered a catastrophic failure on June 5, 1976, as it was filling for the first time. The collapse of the dam resulted in the deaths of 11 people and 13,000 cattle. The dam cost about $100 million to build, and the federal government paid over $300 million in claims related to its failure. Total damage estimates have ranged up to $2 billion. The dam has not been rebuilt. More details