The Johnstown Flood of May 31, 1889, was responsible for more recorded deaths than any other disaster in the United States until the Galveston hurricane of 1900.1 An important difference between the two is that the Johnstown flood was not a natural disaster. Although the Johnstown region was in the midst of a particularly wet spring and the former boroughs that now form the city of Johnstown were already experiencing low-level flooding on May 31, the ultimate reason for the high death toll was the catastrophic failure of the South Fork Dam, located fourteen miles upstream from the outskirts of Johnstown on the South Fork of the Little Conemaugh River (see fig. 1). The millions of tons of water released by the failure of the dam caused devastation along the Little Conemaugh River drainage. As the water moved downstream it was temporarily impounded by debris dams behind two Pennsylvania Railroad bridges (Viaduct and Bridge no. 6), which caused "reformation of the lake" at these points. When Bridge no. 6 failed, the rejuvenated flood wave sped toward Johnstown. Most structures [End Page 335] were no match for the violent floodwaters, which carried debris from the dam itself, trees, houses, bridges, railroad cars, barbed wire; even livestock and people were caught in the torrent. By the time the flood wave reached the Stone Bridge in Johnstown, it had traveled about sixteen miles. At this point most of its energy was spent and a huge debris jam formed at the bridge. The debris jam subsequently caught fire, claiming additional victims who had been trapped among the debris. In the end, over 2,200 people lost their lives.
Despite the infamy of the Johnstown Flood of 1889 (or perhaps because of it), there is much conflicting, and sometimes inaccurate, information surrounding the factors contributing to the flood and the flood itself. This article reviews the events leading up to the flood and provides new insights as to the cause of the dam's failure, with respect to the fill material used in its reconstruction, the rainfall amounts and intensity, the rate of floodwater runoff into Lake Conemaugh (previously known as the South Fork Reservoir), and the travel time of the flood wave to Johnstown. Special attention is given to resolving the conflicting accounts as to the time of failure for the South Fork Dam, the volume of Lake Conemaugh at the time of the dam failure, the length of the dam's embankment, and the time it took to drain the lake. Finally, we hope to show that the often-presented idea that the designed
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spillway for the original dam was inadequate is without merit and that indeed the culpability for this tragedy rests in large part with the actions/ inactions of the South Fork Hunting and Fishing Club.
Original South Fork Dam
The South Fork Dam was designed to hold back water that could be used as a dry-season water supply for the Pennsylvania Main Line Canal, with released water traveling down the Little Conemaugh River to the Johnstown terminus of the canal. William E. Morris, one of the state engineers of the Western Division of the Pennsylvania Canal, prepared the dam's original design in 1839.2 Authorization for dam construction contracts and iron work occurred in January 1840 and work began in April of that year.3 Due to Pennsylvania's financial difficulties, funding for the project ran out in 1842 and Morris, along with the other engineers, lost their employment with the Canal Commission. Nevertheless, Morris prepared a modified design in 1846 that would reduce some of...