THE JOHNSTOWN FLOOD OF 1889 – CHALLENGING THE FINDINGS OF THE ASCE INVESTIGATION REPORT
We challenge that conclusion based on hydraulic analyses of the dam as originally built, estimates of the time to peak and time of concentration for the South Fork watershed, and contemporary reports of conditions in the watershed. Our analysis using LiDAR data provides an updated volume of 1.455 × 107 m3 for Lake Conemaugh at the time of dam failure. We generated hydrographs of lake stage decline and flood discharge. More than an hour would have been needed to drain most of Lake Conemaugh, with peak dam breach discharges ranging from 7200 to 8970 m3 s-1. The dam as originally built in 1853 had a crest nearly 1 m higher and the added capacity of 5 discharge pipes and an auxiliary spillway; its safe discharge capacity was more than twice that of the Club’s reconstructed dam. Had the Club not fatally lowered the dam crest, the South Fork dam would not have overtopped in 1889 and would likely have survived the flood event.
The committee completed their investigation in 7 months, on Jan. 15, 1890, but their report was sealed and not given to the ASCE membership. At the annual ASCE convention of June 1890, Max Becker stated that “We will hardly [publish our] report this session, unless pressed to do so, as we do not want to become involved in any litigation” [Johnstown Tribune, 8/27/1890]. Although many members clamored for the report, it was not published in ASCE’s Transactions until June 1891, two years after the disaster. The report contains discrepancies in key observations and placed undue reliance on extreme reservoir inflow estimates. Their confidence that dam failure was inevitable was incompatible with information that was readily available to the committee.
Our journal paper is licensed open access (CC BY-NC-ND) and can be downloaded at http://www.heliyon.com/article/e00120/.