The Johnstown Flood, sometimes referred to locally as Great Flood of 1889, occurred on Friday, May 31, 1889, after the catastrophic failure of the South Fork Dam, located on the south fork of the Little Conemaugh River, 14 miles (23 km) upstream of the town of Johnstown, Pennsylvania, United States. The dam ruptured after several days of extremely heavy rainfall, releasing 14.55 million cubic meters of water. With a volumetric flow rate that temporarily equaled the average flow rate of the Mississippi River, the flood killed 2,208 people and accounted for US$17,000,000 in damage.
Debris of Stone Bridge in Johnstown following the flood
The remaining abutment of the South Fork Dam with the US-219 highway bridge downstream in the background
Remains of the South Fork Dam abutment with US-219 downstream in the background as it appeared in 1980
Remains of South Fork Dam showing construction details of the dam as it appeared in 1980
A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many other disciplines in which total and irrecoverable loss occurs, such as a head crash occurrence on a hard disk drive.
Original Tay Bridge from the north
Fallen Tay Bridge from the north