1977 — July 19/20, Rain, Dam Failure, flash floods, Johnstown, Tanneryville, PA — ~85

— ~85 Blanchard. (We take the Johnstown Flood Museum tally to be authoritative.)

–76-86 U.S. Comptroller General (GAO). The Johnstown Area Flood of 1977. 1978, p. 1.*
–78-86 Hoxit, et al. (NOAA/USGS). Johnstown-Western PA Storm…Floods…1977. 1982, 1.**
–78-86 Kozlovac. Adventures in Flood Control: The Johnstown, Pennsylvania Story. 1995, p.10.***
— 85 Hamburg. “Tanneryville man remembers devastation from 1977 Johnstown Flood.” 7-19-2017.
— 85 Johnstown Flood Museum. 1936 & 1977 Floods. Johnstown Area Heritage Assn., 2020.
— 84 History.com. This Year in History, Disaster, July 20, 1977. Second Flood Hits Johnstown
— 78 USGS. Summary of Significant Floods in…US…PR…VI, 1970 Through 1989. 2008.
— 77 Cornell, James. The Great International Disaster Book (Third Edition). 1982, p. 187.
— 77 Gelber. The Pennsylvania Weather Book. 2006, 214.
— 76 Ludlum. The American Weather Book. 1982, pp. 82, p. 161.
— 40 US DHS. Dams Sector: Estimating Loss of Life for Dam Failure Scenarios. 2011, p.76.

* “Seventy-six people were killed (10 more are missing)…”
** “At least 78 deaths were attributed to the floods, and eight persons were still listed as missing 1 year later.”
***Seventy-eight deaths and eight missing, which, if added to the known deaths comes to 86.

Narrative Information

Cornell: “The ill-fated city of Johnstown, site of the most famous flood in American history, in 1889, again suffered a massive deluge, this time killing 77 people, destroying 500 homes, damaging another 2,000, producing $200 million in damages, and costing at 1,000 jobs due to plant and shop closings.

“The second great Johnstown flood was caused by a heavy rainfall – nearly 9 inches in 8 hours – that overwhelmed flood-control systems and broke the Laurel Run Dam, sending some 100 million gallons of water pouring into the streets.

“Some victims were not found for months, with the body of one little girl discovered in the Conemaugh River on May 31, 1978, nearly a year later. The girl’s sister, brother, and mother also died in the flood.” (Cornell. The Great International Disaster Book (Third Edition). 1982, p. 187.)

DHS: “Laurel Run Dam was located on Laurel Run approximately 4 miles north of Johnstown (Laurel Run Dam should not be confused with the South Fork Dam which failed in 1889. Laurel Run Dam was located approximately 8 air miles from the South Fork Dam). After flowing out of Laurel Run Dam, water traveled approximately 2.5 miles before entering the Conemaugh River at a point that is approximately 3 river miles downstream from Johnstown. The earthfill dam was constructed to provide a water supply.

“The dam failed at 2:35 am on Wednesday, July 20, 1977. The 63-year-old dam failed from overtopping during an area-wide storm (flood damage occurred throughout the Johnstown area).

“Laurel Run Dam had a height of 42 feet. The reservoir had a storage capacity of 310 acre-feet with the reservoir at the spillway crest. The amount of water in the reservoir when it failed is not known, but perhaps was approximately 450 acre-feet.

“The National Weather Service did not issue any flash flood watches or warnings for the Johnstown area until 2:40 am. The flashflood warning issued at that time was generic and did not name any specific area or stream within the two counties for which the warning applied.

“There was no one at the site to observe the dam and no one decided to warn or evacuate. No warnings were issued in the 2.5-mile-long reach where the greatest devastation occurred. In addition, cues of the approaching dam failure floodwave, which might have allowed for a last-minute escape, may have gone unnoticed. Any last-minute escape/evacuation that did occur was surely hampered by the rain and darkness that accompanied the arrival of dam failure flooding. About 30 houses suffered major damage in the 2.5-mile-long reach. A memorial and plaque at the mouth of Laurel Run listed 40 different names when viewed in 1981 and it is presumed that all of the fatalities occurred in the first 2.5 miles downstream of the dam….The dam was not rebuilt….” (US DHS. “Laurel Run Dam, Pennsylvania – Failed in July 1977,” pp. 76-77 in: Dams Sector: Estimating Loss of Life for Dam Failure Scenarios. 2011.)

Gelber: “”History would sadly be repeated on a steamy July night in 1977, when a small cluster of thunderstorms seemed to stall, or essentially regenerate over the Conemaugh Valley and the surrounding mountains above Johnstown on the night of July 19.

“The thunderstorm complex brought heavy rain commencing around 8:30 p.m. on the nineteenth…and did not let up until around 4:30 a.m. in the morning of the twentieth. Rainfall totals as high as 12.00 inches were measured in West Taylor Township northwest of Johnstown. Torrents of water poured off the deep hillsides of Cambria County into the Little Conemaugh River, which meets the Conemaugh just above Johnstown. A break in the Laurel Run Dam sent an angry wall of rushing water 10 feet high through the valley into Johnstown without warning, sweeping way unsuspecting residents in their homes and cars….

“The flash flood that struck Johnstown in July 1977 took at least seventy-seven lives and caused $424 million of damage…” (Gelber. The Pennsylvania Weather Book. 2006, 213-214.)

Hamburg: “West Taylor Township — There are countless stories to tell from the 1977 flood, which happened 40 years ago this week. And one area hit the hardest was Tanneryville. Out of the 85 people who died in the flood, nearly half lived in Tanneryville….

“What gave way was the Laurel Run Dam. Rushing water devastated the community of Tanneryville and continued rushing to the city of Johnstown….” (Hamburg, D. “Tanneryville man remembers devastation from 1977 Johnstown Flood.” WJAC TV6, Johnstown, PA, 7-19-2017.)

History.com: “A flash flood hits Johnstown, Pennsylvania, on this day in 1977, killing 84 people and causing millions of dollars in damages. This flood came 88 years after the infamous Great Flood of 1889 that killed more than 2,000 people in Johnstown. As they had in the first flood, the dams in the Conemaugh Valley failed, bringing disaster to the town.

“The flood occurred when an extraordinary amount of rain came down in the Conemaugh Valley in a short period of time. Nearly 12 inches were measured in 10 hours. 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.

“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. President 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.” (History.com. This Year in History, July 20, 1977. “Second Great Flood Hits Johnstown.”)

Kozlovac: “Between the afternoon of July 19th, and the morning of July 20th, 1977, the people of Johnstown found out that their city which was touted to be flood proof was indeed still vulnerable to Mother Nature’s ravages. During this period, two major squall lines moved across Pennsylvania. The first storm formed just west of Pittsburgh and moved east-southeastward dropping approximately one inch of precipitation over the Johnstown area. The second line of thunderstorms formed over northwestern Pennsylvania and slowly moved toward the southeast. The second line of storms became quasi-stationary above the Johnstown area. Radar information during the period of storm activity indicated that twelve separate thunderstorm cells moved over the Johnstown area. These storms let loose blinding and deafening displays of thunder and lightning. The bulk of the precipitation fell during a period of 6-9 hours over the Johnstown area. My hometown of Nanty Glo, Pennsylvania, which is 10 miles north of Johnstown, received 12 inches of rain during the 24hours in which the storm occurred. To illustrate how localized the brunt of the storm actually was, areas 30 miles to the southwest of Johnstown received negligible or no precipitation during the same 24 hour period. This excess rainfall caused the Conemaugh River flood, its discharge was measured as 115,000 feet per second. The Channel Improvement was designed to contain only 81,500 cubic feet per second. By dawn, Johnstown was at least under six feet of water, which covered 64% of the city’s land area. The U.S. Geologic Survey (U.S.G.S.) and the Army Corps of Engineers classified the July, 1977 flood, as being a 500 year flood. The stage at the Conemaugh River gauging station reached 95% of the Army Corps of Engineers estimated standard project flood.

“The heavy rains had also caused seven privately owned, earthfill, gravity-type dams to fail. The collapse of the Laurel Run Dam however, was the only dam failure which resulted in fatalities. The Laurel Run Dam was the largest of the seven earth work dams which failed with a 101 million gallon capacity. When the dam broke the water which was held back poured down on the small village of Tanneryville killing forty-one people. Of the other dams which failed two were considered minor dams and the remaining four were small dams built without state permits.

“After the rain had stopped and flooding had subsided the job of sorting through the aftermath began. It was found that 78 people had lost their lives during the flood and eight people were missing. There was also 2,700 other individuals who were either sick or injured due to the flood. The city of Johnstown had suffered an estimated 117 million dollars in property damages, while damages to the surrounding areas was estimated at 213 million dollars. On July 21, 1977, the President of the United States declared Johnstown a disaster area. The Red Cross reported that 413 houses, 135 mobile homes, and 52 housing units were totally destroyed, while 5,256 dwelling units sustained major damage. 405 business structures were also destroyed of which half were located in downtown Johnstown. Bethlehem Steel Corporation, the area’s largest employer, estimated that total damages to its facilities would total 35-40 million dollars. Over the next year, the federal government would spend nearly 200 million dollars on the Johnstown area, for rebuilding damaged facilities and loaning funds or giving grants to property owners for reconstruction and repair….” (Kozlovac, Joseph P. Adventures in Flood Control: The Johnstown, Pennsylvania Story. Urban Areas as Environments, 4-19-1995, pp. 9-10.)

NOAA: “The Johnstown, Pennsylvania, area experienced flash flooding as a result of almost continuous rains from about 7:00 p.m., July 19 to 4:00 a.m., July 20. Rainfall intensities during much of this time averaged 2 in/hr., with maximum rainfall totals of 12 in. recorded northeast of Johnstown” (National Oceanic and Atmospheric Administration, 1977).

USGS: “Flooding was severe along the east side of the Allegheny River Basin. Johnstown, located where the Stonycreek and Little Conemaugh Rivers join to form the Conemaugh River, was adversely affected by the flood. Water 4 to 8 ft deep flowed through the downtown streets.

“Seven earth-fill, gravity-type dams failed in the area. The worst dam failure, located on Laurel Run, caused 44 deaths. Maximum discharges of record were recorded at 11 streamflow-gaging stations in the area. Of these 11 stations, 6 recorded discharges with recurrence intervals of 100 years or greater. Overall, the catastrophic floods were responsible for 78 deaths (Paulson and others, 1991), destroying 413 dwellings and causing major damage to 1,363 homes. Eight counties were declared Federal disaster areas, and an estimated $300 million in damages occurred (Paulson and others, 1991).” (USGS. Summary of Significant Floods in…US…PR…VI, 1970 Through 1989. 2008.)

Sources

Comptroller General of the United States. Report by the Comptroller General of the United States – The Johnstown Area Flood of 1977: A Case Study For the Future. Washington, DC: US General Accounting Office, 5-12-1978, Accessed 4-29-2020 at: https://www.gao.gov/assets/130/122799.pdf

Cornell, James. The Great International Disaster Book (Third Edition). New York: Charles Scribner’s Sons, 1982.

Gelber, Ben. The Pennsylvania Weather Book. Piscataway, NJ: Rutgers University Press, 2002. Google preview accessed 1-4-2018 at: http://books.google.com/books?id=34RKv9fMFo4C&printsec=frontcover#v=onepage&q&f=false

Hamburg, Daniel. “Tanneryville man remembers devastation from 1977 Johnstown Flood.” WJAC TV6, Johnstown, PA, 7-19-2017. Accessed 4-29-2020 at: https://wjactv.com/news/local/tanneryville-man-remembers-devastation-from-1977-johnstown-flood

History.com. This Day in History, Disaster, July 20, 1977. “Second Great Flood Hits Johnstown.” Accessed 12-7-2008 at: http://www.history.com/this-day-in-history.do?action=tdihArticleCategory&displayDate=07/20&categoryId=disaster

Hoxit, L. Ray, Robert A. Maddox, Charles F. Chappell (NOAA), and Stan A. Brua (USGS). Johnstown-Western Pennsylvania Storm and Floods of July 19-20, 1977 (Geological Survey Professional Paper 1211). U.S. Geological Survey and National Oceanic and Atmospheric Administration. Washington, DC: U.S. Gov. Printing Office, 1982. Accessed 4-29-2020 at: https://www.google.com/books/edition/Johnstown_western_Pennsylvania_Storm_and/hUziJP0qidoC?hl=en&gbpv=1&dq=Johnstown-Western+Pennsylvania+Storm+and+Floods+of+July+19-20,+1977&printsec=frontcover

Kozlovac, Joseph P. Adventures in Flood Control: The Johnstown, Pennsylvania Story. Urban Areas as Environments, 4-19-1995. Accessed 4-29-2020 at: https://www.nwrfc.noaa.gov/floods/papers/Johnstown_flood.pdf

Ludlum, David M. The American Weather Book. Boston: Houghton Mifflin Co., 1982.

United States Department of Homeland Security. Dams Sector: Estimating Loss of Life for Dam Failure Scenarios. September 2011, 94 pages. Accessed 12-2-2017 at: https://www.hsdl.org/?view&did=726315

United States Geological Survey. Summary of Significant Floods in the United States, Puerto Rico, and the Virgin Islands, 1970 Through 1989 (Water-Supply Paper 2502). USGS Kansas Water Science Center, Sep 17, 2008. Accessed 11-12-2016 at: http://ks.water.usgs.gov/pubs/reports/wsp.2502.contents.html#HDR1