Coleman commented on the discrepancy in a Pittsburgh Post-Gazette story. Although the incidents were similar, the engineers presented very different findings. Two of the engineers who investigated the Johnstown flood had previously investigated the failure of the Mill River Dam in Massachusetts in 1874. 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. The dam as originally designed and built would never have been overtopped and destroyed by the 1889 storm.Ĭoleman 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. Such extreme conditions did not exist then because local streams reached maximum flood levels hours before the dam breach. 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. They asserted that the rainfall was so great the dam would have failed even if it had been rebuilt to its original design. An 1891 report by the American Society of Civil Engineers blamed the flood on unusually heavy rainfall. The luxury outdoor club’s members included industrialists Andrew Carnegie, Henry Clay Frick and Andrew Mellon. 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 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. Those changes included impeded drainage and the lowering of the crest. 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. 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. 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. The researchers found that the Club's employees had lowered the dam's crest by nearly three feet, one foot more than previously reported. "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. 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. The report is the result of five years of research. 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. 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. Had the Club repaired the dam to its original 1839 specifications it would likely have survived the storm of May 30-31, 1889. It stated that, before the Club acquired the property, the dam had partially breached in 1862. Their report concludes that changes to the South Fork Dam by the South Fork Fishing & Hunting Club doomed the dam to fail. 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.
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