Widespread thunderstorms associated with two major squall lines, moved across Pennsylvania between the afternoon of July 19 and morning of July 20, 1977. The western part of outflow boundary produced by the second line became almost stationary in western Pennsylvania and resulted in 6 to 9 hours of nearly continuous thunderstorms. More than 6 inches of rain fell over a 400-square-mile area during this period. In the hills just north and east of Johnstown, rainfall totals were as much as 12 inches. Flash flooding was severe as the storms moved slowly southeastward across the Allegheny, Susquehanna, and Potomac River basins. Peak natural runoff rates greater than 1,000 cubic feet per second per square mile were common for streams draining up to 10 square miles. At eight gaging stations, recurrence intervals for the peak discharges were estimated to be 100 years or more. In addition to high surface runoff, some disasterous flooding also resulted from the failure of seven earthfill-gravity-type dams. At least 78 deaths were attributed to the flooding and eight persons were still listed as missing 1 year later. Total damages in the eight-county flood area were extremely high, possibly exceeding $500 million.
Johnstown-Western Pennsylvania Storms and Floods of July 19-20, 1977
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Widespread thunderstorms associated with two major squall lines, moved across Pennsylvania between the afternoon of July 19 and morning of July 20, 1977. The western part of outflow boundary produced by the second line became almost stationary in western Pennsylvania and resulted in 6 to 9 hours of nearly continuous thunderstorms. More than 6 inches of rain fell over a 400-square-mile area during this period. In the hills just north and east of Johnstown, rainfall totals were as much as 12 inches. Flash flooding was severe as the storms moved slowly southeastward across the Allegheny, Susquehanna, and Potomac River basins. Peak natural runoff rates greater than 1,000 cubic feet per second per square mile were common for streams draining up to 10 square miles. At eight gaging stations, recurrence intervals for the peak discharges were estimated to be 100 years or more. In addition to high surface runoff, some disasterous flooding also resulted from the failure of seven earthfill-gravity-type dams. At least 78 deaths were attributed to the flooding and eight persons were still listed as missing 1 year later. Total damages in the eight-county flood area were extremely high, possibly exceeding $500 million.
In July 1977, the Johnstown, Pennsylvania, area was declared a major disaster area after a flood struck 136 communities in 8 counties and killed 76 people, injured or caused illness to 2,700, and...
This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it.This work is in the "public domain in the United States of...
This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and...
This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it.This work is in the "public domain in the United States of...
History of the Johnstown Flood - With full accounts also of the destruction on the Susquehanna and Juniata rivers, and the Bald Eagle Creek - Vol. 1 is an unchanged, high-quality reprint of the...
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