The second “great flood” to hit Johnstown, Pa., happened on July 20, 1977.

It was, however, the third flood to devastate the town in Cambria County - the first in 1889 killed more than 2,000 people, the second in 1936 killed two dozen people and the 1977 flood killed 84 people.

In 1977, after nearly 12 inches of rain fell in 10 hours, five dams failed, inundating the area with millions of gallons of water.

Swirling muddy water flows across a roadway in a residential area where homes have been completely demolished in the aftermath of a flood in Johnstown, Pa., Wednesday, July 20, 1977. Damage is in millions of dollars and several people have been killed as a result of the floods caused by bursting dams overwhelmed by heavy rainfall. (AP Photo/Paul Vathis)

According to www.history.com, “The National Weather Service later estimated that this amount of rain in that location should happen less than once every 1,000 years.”

"The largest dam that burst was at Laurel Run. This 10-year-old earthen dam held back 100 million gallons of water. Despite having a 42-foot-high spillway, the dam failed and the resulting flood devastated the town of Tanneryville. Five other dams in the area also burst, releasing another 30 million gallons of water over the landscape.

Rescue workers use a makeshift bridge across a tributary of the Conemaugh Creek to remove the body of an unidentified flood victim in Johnstown, Pa., July 20, 1977. Heavy overnight rains and the breaking of a dam caused extensive flooding, with at least 3 people dead and damage estimated at $100 million. (AP Photo/Paul Vathis)

The failure of the dams came as a big surprise. Johnstown had constructed an entire system designed to completely eliminate the flood risk. In addition, regular inspections had turned up no defects. Still, the dams were no match for the thunderstorm that stalled over the area on July 20.

In addition to the 84 people who lost their lives to the flood, $300 million in damages were suffered and hundreds of people lost their homes.

City Hall is reflected in the flood that remains in the downtown area in Johnstown, Pa., early Thursday morning, July 21, 1977. Heavy rainfall of at least 12 inches and the breaking of a dam caused the town to be flooded Wednesday morning. (AP Photo)

President Jimmy Carter declared the region a federal disaster area and the National Guard was sent to assist in the relief efforts. Despite millions spent to rehabilitate the Johnstown area, the economy never recovered. The city’s population decreased nearly 15 percent in the aftermath of the flood, as people moved away to rebuild their lives elsewhere."

According to the Johnstown Flood Museum the water from a line of thunderstorms caused small streams to overflow. Those streams "carved new channels and smashed through expressways, apartment buildings, factories and homes. An earthen water supply dam collapsed at Laurel Run Reservoir, one of several dams that failed. The waters overflowed the channel system in Johnstown that was to have left the city 'flood-free.' However, according to later estimates by the U.S. Army Corps of Engineers, the water level could have been as much as 11 feet higher if the channel system had never been built.

The body of a woman is removed from debris below the Tanneryville section of Johnstown, Pa., Friday, July 22, 1977. The area was washed away early Wednesday when a dam broke from the pressures of a heavy rain storm. Fifty bodies have been found. (AP Photo)

The Red Cross, Salvation Army, other non-profit agencies, the state and federal governments, and private individuals rushed to help. On July 21, President Jimmy Carter declared the worst-hit counties a federal disaster area (Cambria, Somerset, Indiana, Bedford, Westmoreland, Clearfield, and Jefferson; a few days later, Blair was added). The National Guard was mobilized, and the U.S. Army Corps of Engineers arrived to assist in debris removal and demolition of non-salvageable buildings.

... The 1977 flood was a blow to Johnstown's increasingly fragile economy. Many downtown firms damaged by the flood did not reopen or moved to the suburbs. Employment at Bethlehem Steel dropped by 4,000. Between 1970 and 1980, the city's population dropped from 42,221 to 34,221, a 19.4% decline, and the 1977 flood is a major reason why."

The flood museum has an archive of oral histories from survivors of the flood.

A helicopter hovers over a residential area where homes have been completely demolished in the aftermath of a flood in Johnstown, Pa., Thursday, July 21, 1977. Damage is in millions of dollars and several people have been killed as a result of the bursting dams overwhelmed by heavy rainfall. (AP Photo/Paul Vathis)A youngster flies the American flag from the collapsed second story of his home after returning to his home in Johnstown, Pa., Friday, July 22, 1977. This section of the home was separated from the first floor and floated downstream after at least 12 inches of rain fall in the mountainous region, causing a flood July 20. (AP Photo)

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