Hydraulic Calculations

Abstract

Calculations are used to examine the hypothetical scenario described by Francis et al. (1891) in which they assert that the South Fork dam would have failed even had it been repaired as originally built in the 1850’s. Analysis I have added a sentence below to call out the footnote there. (This research relies on nineteenth century publications and more recent works that document historic data using English units rather than SI units. For most of the calculations I use the always preferable SI units, but when depending on old data sources the original English units are given. This approach will help confirm appropriate use of the nineteenth century data and will aid future workers who may further analyze this dam breach disaster) is provided for the pipe flows, flows through the main and auxiliary spillways, and the rate of storm runoff into Lake Conemaugh. Hydrographs were prepared to show how lake levels and discharges through the breach diminished over time. The lake required more than an hour to drain. The discharge capacity of the original dam is compared with the reduced discharge capacity of the dam as severely modified by the South Fork Fishing & Hunting Club. Changes made by the Club, especially lowering of the embankment crest, were fatal. They cut the safe discharge capacity in half and doomed the dam and the towns below it to inevitable destruction.

“I shall try to correct errors when shown to be errors, and I shall adopt new views so fast as they shall appear to be true views.”

—Abraham Lincoln, in Letter to Horace Greeley, Aug. 22, 1862