| July 19, 1977 to July 20, 1977|
Johnstown, Pennsylvania area
US$117 million: Johnstown; $213 million: Surrounding areas
The Johnstown flood of 1977; also known as the Second great flood of Johnstown, and the Johnstown disaster, began on the night of 20 July 1977 when flash floods hit the area of Cambria County, around Johnstown, Pennsylvania and the Conemaugh Valley. Nearly twelve inches of rain fell in twenty-four hours, when a thunder storm stalled over the area. With the failing of six area dams nature was able to do what area residents had been convinced could not happen again.
Ron Shawley, executive director of Laurel Highland's Historical Village, returned to Johnstown on the 20th and stated "It was like somebody dropped an atomic bomb on Johnstown", "I questioned what kind of force it would take to do that.".
After the Johnstown flood of 1936, the Army Corps of Engineers began a study and work started in August 1938 with extensive dredging and flood control measures. On November 27, 1943, Colonel Gilbert Van B. Wilkes, Chief of the Army Corps of Engineers, Pittsburgh District, told a Johnstown audience the flood problems had been effectively solved. People began to feel secure that any flooding issues had been resolved and even promoted the area as "flood free" for many years. The Corps of Engineers had designed flood control measures for protection of a standard project flood. Protection to the 500 year level was not economically viable. In 1974 the Corps issued a report titled "The Potential for Future Flooding in the Johnstown Area". This did not deter town leaders and the people of Johnstown at all.
On the 19 July 1977 a deluge of rain hit the area around Johnstown during the night and the dams in the area over-topped and failed. The largest dam to fail was the Laurel Run Dam releasing over 101 million gallons of water that poured through the village of Tanneryville killing 41 people. The combination of the other five dams released another 27 million gallons, not counting the water from rains. Well over 128 million gallons of water poured down the valley from the dams alone and by dawn Johnstown was flooded by six feet of water. The channel improvements were designed to carry 81,500 cubic feet per second but the flood discharge was measured as 115,000 feet per second.
Johnstown flood of 1977 Wikipedia
A Swiss immigrant named Joseph Schantz started farming at the confluence of the Little Conemaugh River and the Stoneycreek River around 1794. He laid out plans for a town and chose the name Conemaugh after a Native American village that occupied the same site. The plan accounted for the fact that a new county named Cambria would be taken from Somerset County but lobbying for the new town to be the county seat failed as Ebensburg was chosen. The town was situated within the Conemaugh River sub-basin (Ohio River Basin) and was prone to flooding.
After the flood of 1889 no significant flood measures were undertaken. In 1936 Congress was looking at flood control bills. During this time Heavy snow run-off and three days on continuous raining caused the Saint Patrick's Day flood of 1936 occurred. On April 27, 1937, Congress passed sweeping flood control legislation and in 1938 work began. On November 27, 1943, the Johnstown Channel Improvement Project was completed. 9.1 miles of improvements that included the Conemaugh River, Stony Creek, and the Little Conemaugh River.
The Laurel Run Dam on Laurel Run was an old earthen dam owned by the Bethlehem Steel company and sold to the Johnstown Water Company. This dam had a 42.5-foot high spillway, and when it failed about 101 million gallons of water was released. After the dam failed water rushed through the Tanneryville neighborhood. The Sandy Run Dam, a 28-foot high, 63-year old earthen dam with a spillway owned by the Highland Water and Sewer Authority, released a little more than 18 million gallons of water. When the dam failed the flood waters entered the Conemaugh between St. Michael and South Fork at Ehrenfeld. The Salix Water Dam on Otto Run, owned by the Adams Township Water Authority, was a 25-foot earthen dam that held 2 million gallons of water. When the dam failed the flood waters ran into the South Fork Little Conemaugh River which joins the Conemaugh River in Sidman. The Cambria Slope Mine #33, on Sanders Run, had a spillway height of 32 feet and was leased by the Bethlehem Mines Corporation, and held 7 million gallons of water. Sanders Run flows adjacent to and joins Howells Run, skirting Ebensburg draining into City Reservoir. The dam was a total failure. An Unnamed dam on Peggy's Run, Franklin Borough was leased to Bethlehem Mines Corporation. The dam was situated outside Franklin and the water shed drained towards East Conemaugh and the Conemaugh River. The dam failure released an unknown amount of water. An unnamed impoundment dam, holding 1000 gallons of reserve water for Bethlehem Mines Corporation also failed.
The victims of the 1977 flooding were from Old Conemaugh Borough (2), Hornerstown (4), Walnut Grove (3), West End (1), Dale Borough (10), Seward (7), Strongstown (1), Tanneryville (39 including those still missing), Windber, (2), Summerville (1), Dilltown (1), Dunlo (3), Mineral Point (2), Richland (6), and Scalp Level (2)