Researchers from the University of Pittsburgh at Johnstown used hydrology and mapping expertise to challenge the 127-year-old findings of the cause of the 1889 Johnstown Flood.
Their report concludes that changes to the South Fork Dam by the South Fork Fishing & Hunting Club doomed the dam to fail. It stated that, before the Club acquired the property, the dam had partially breached in 1862. Had the Club repaired the dam to its original 1839 specifications it would likely have survived the storm of May 30-31, 1889.
Pitt-Johnstown instructor Neil M. Coleman and the late professor emeritus Uldis Kaktins teamed with researcher and Pitt-Johnstown alumna Stephanie Wojno to analyze the hydraulics of the dam as originally built in 1852 versus the Club's reconstructed dam.
Their article was published June 16, 2016, in the journal Hydrology, Volume 2, Issue 6, and titled Dam-Breach hydrology of the Johnstown flood of 1889–challenging the findings of the 1891 investigation report.
The report is the result of five years of research. According to the publication, the geologists modeled the hydraulics of the dam and used published LiDAR data (an infrared laser-based mapping system) to digitally recreate the onetime dam and lake that once served as the South Fork Fishing and Hunting Club's summer getaway.
"We had a GPS survey conducted that allowed us to estimate the lake levels at the time the dam failed," Coleman told the Johnstown Tribune-Democrat, crediting Musser Engineering of Central City and Pitt-Johnstown engineering professor Brian Houston for partnering in that effort. The researchers found that the Club's employees had lowered the dam's crest by nearly three feet, one foot more than previously reported.
They also found that the lowering of the dam eliminated the action of an emergency spillway that was provided in the original design to protect the dam during floods. By making that move and failing to replace five discharge pipes, the Club members "drastically affected that dam's ability to discharge storm water," Coleman said.
The geologists’ report concluded that changes to the dam prior to its failure had reduced by one-half the dam’s ability to discharge storm water. Those changes included impeded drainage and the lowering of the crest. The South Fork Dam was the largest earth dam (made of dirt and rock, rather than steel and concrete) in the United States, and Lake Conemaugh was the largest man-made lake at the time. The embankment of the South Fork dam measured 860-feet-wide by 72-feet-high, according to a 2013 article published in Pennsylvania History by Kaktins, Carrie Davis Todd, Wojno, and Coleman.
The luxury outdoor club’s members included industrialists Andrew Carnegie, Henry Clay Frick and Andrew Mellon. An 1891 report by the American Society of Civil Engineers blamed the flood on unusually heavy rainfall.
They asserted that the rainfall was so great the dam would have failed even if it had been rebuilt to its original design.
The discharge capacity of the original dam was more than twice that of the reconstructed dam and therefore could have avoided overtopping during the 1889 storm for as much as 14 hours even under extreme conditions of inflows to the lake. Such extreme conditions did not exist then because local streams reached maximum flood levels hours before the dam breach. The dam as originally designed and built would never have been overtopped and destroyed by the 1889 storm.
Coleman and his fellow researchers found evidence that the original dam with its higher crest survived a flood event shortly after it was built, in the spring of 1856 following a rapid snowmelt in the region. At the time the dam was at its design height and appears to have performed as intended, with two operating spillways and discharge pipes also in use.
Two of the engineers who investigated the Johnstown flood had previously investigated the failure of the Mill River Dam in Massachusetts in 1874. Although the incidents were similar, the engineers presented very different findings. Coleman commented on the discrepancy in a Pittsburgh Post-Gazette story. “In that (Mill River) report, they lambasted the whole operation. The owners, the materials they used, the builders - everything,” he said. “But you see an entirely different philosophy appear at Johnstown, when they’re investigating a dam owned by the greatest industrialists and financiers in the country.”
The dam gave way on May 31, 1889, causing the Johnstown Flood's historic toll:
- 14.3-million tons of water from Lake Conemaugh rushed 14 miles downstream to Johnstown, according to the Hydrology report's Analysis section
- more than 2,200 people killed
- 33 train engines were pulled into the raging waters, creating greater hazards, according to History.com
At the time, it represented the single greatest loss of life in American history, according to the Johnstown Flood Memorial Museum.
A Post-Gazette editorial on July 13, 2016, noted: “The newest chapter on the Johnstown flood, written not by historians but geologists, fixes blame for the disaster squarely on a sports club owned by some of Pittsburgh’s industrial tycoons. The study represents an important convergence of academic disciplines and sheds new light on a tragedy that still haunts the region.”
Notes:
- Dr. Kaktins died on July 2, 2016.
- Coleman was supported in part by the Department of Energy and Earth Resources, University of Pittsburgh at Johnstown.
- The photo at the top of the page shows workers clearing debris from the Stone Bridge in Johnstown after the flood in 1889. (National Park Service)