Neil M. Coleman

Dam-Breach hydrology of the Johnstown flood of 1889-challenging the findings of the 1891 investigation report.

In 1891 a report was published by an ASCE committee to investigate the cause of the Johnstown flood of 1889. They concluded that changes made to the dam by the South Fork Fishing and Hunting Club did not cause the disaster because the embankment would have been overflowed and breached if the changes were not made. We dispute that conclusion based on hydraulic analyses of the dam as originally built, estimates of the time of concentration and time to peak for the South Fork drainage basin, and reported conditions at the dam and in the watershed. We present a LiDAR-based volume of Lake Conemaugh at the time of dam failure (1.455 × 107 m3) and hydrographs of flood discharge and lake stage decline. Our analytical approach incorporates the complex shape of this dam breach. More than 65 min would have been needed to drain most of the lake, not the 45 min cited by most sources. Peak flood discharges were likely in the range 7200 to 8970 m3 s−1. The original dam design, with a crest ∼0.9 m higher and the added capacity of an auxiliary spillway and five discharge pipes, had a discharge capacity at overtopping more than twice that of the reconstructed dam. A properly rebuilt dam would not have overtopped and would likely have survived the runoff event, thereby saving thousands of lives. We believe the ASCE report represented state-of-the-art for 1891. However, the report contains discrepancies and lapses in key observations, and relied on excessive reservoir inflow estimates. The confidence they expressed that dam failure was inevitable was inconsistent with information available to the committee. Hydrodynamic erosion was a likely culprit in the 1862 dam failure that seriously damaged the embankment. The Club’s substandard repair of this earlier breach sowed the seeds of its eventual destruction.

Day of the Dam Breach

The testimonials taken by the Pennsylvania Railroad in 1889 preserve remarkable eyewitness accounts from the day of the flood, from the early hours that day through the passing of the flood wave. The stories are best told in the words of those witnesses. After getting word of problems on the rails east of Johnstown, PRR executives Michael Trump and Robert Pitcairn boarded trains and headed east. The explicit messages they received about the danger to the South Fork dam gave them both opportunities to warn the towns below that dam and their own employees and passengers along the Little Conemaugh River. Their failure to do so undoubtedly cost many lives.

Biographical Sketches of John G. Parke, Jr. and the Engineers Behind the ASCE Investigation

The life of John G. Parke, Jr. is discussed, before and after he witnessed the breach of the South Fork dam. Most of his career and married life was spent in Monessen, PA. Biographical sketches are presented for the ASCE investigators, engineers James B. Francis, William Worthen, Alphonse Fteley, and Max Becker, outlining their professional and personal lives.

Early History of the South Fork Dam

The history of the dam is intimately linked to the early transportation system in Pennsylvania. Philadelphia had been the center of commerce on the east coast. The success of the Erie Canal brought New York to prominence, surpassing Philadelphia. Prominent Pennsylvanians wanted an equivalent transportation artery to regain their stature. A great canal system and Portage Railroad were built to connect the rivers, east and west. It was soon realized that dams were needed to supply water during dry seasons to maintain the boat traffic. The South Fork dam was planned to supply water to the canal and waterway west of the Alleghenies. After many years of delays it was finally completed in 1852 and provided good service. However, by the mid-1850’s the canal system and its dams were virtually obsolete because trans-state rail service had been established. The entire system was sold to the Pennsylvania Railroad in 1857, but fell into disrepair.

The South Fork Fishing & Hunting Club

The Club begins work at the South Fork dam with a 50-man crew 5 months before John Reilly transferred the property. The Club workers removed the cast-iron discharge pipes as part of a “handshake deal” between Reilly and Ruff. They lowered the crest of the dam and filled in the partial breach of 1862, accomplishing this between late 1879 and early summer of 1881. The Club’s changes fatally weakened the dam and doomed the towns below it. John Fulton inspected the dam on behalf of Cambria Iron but his sensible comments were rebuffed by Ruff. After completing the dam, clubhouse, and other infrastructure, the elite Club officially opened in late July, 1881. The first guest in the ledger book was John Hunt. Several weeks later he returned with Robert Pitcairn.

The Gathering Storm – “A Shower of Fishes”

May of 1889 had unusual weather. The earliest recorded formation of an Atlantic hurricane (up to that time) occurred on May 20th. Less than a month later another hurricane was born. Between these events a low-pressure system developed in the western plains and quickly moved east, pulling in additional warmth and moisture from the south and the Atlantic Coast. Large lateral gradients in temperature and pressure developed, rapidly strengthening the storm. The weather system caused damage over large regions of the northeastern U.S. and especially ravaged Pennsylvania, Maryland, and New York State. Unintentional cloud seeding from the smoky industries in Johnstown may have enhanced local precipitation in 1889; perhaps also in 1936 and 1977.

Analysis of the South Fork Dam and the Former Lake Conemaugh

Key objectives are outlined for the hydrologic calculations of the former Lake Conemaugh and the dam breach flood. Dam remnant survey data collected in 1889 were compared with the modern GPS reference frame. They differ by ~6.2 ft. (1.9 m), the 1889 data being systematically lower. At the moment the dam breached in 1889, the surface of Lake Conemaugh had an elevation in the range of ~492.5 to 492.6 m. Using LiDAR data and this lake stage, a storage-elevation curve was developed for the lake. The impoundment held about 1.455 × 107 m3 of water. The equivalent tonnage (14.3 million) is less than the usually cited figure of 20 million tons. Analysis of the South Fork watershed indicates that the time of concentration for runoff from the major rain event should have been in the range ~3.6 to 7.3 h, and the time to peak discharge less than 7.3 h. Observations of local streams suggest that rivers had peaked between 12 noon and 1:00 p.m. on the day of the flood, several hours before the dam breach.

The Forgotten Dam: The Eastern Reservoir at Hollidaysburg and Its Role in Canal History

Forgotten today, the Eastern Dam and reservoir near Hollidaysburg, Pennsylvania provided dry season flows to the Main Line Canal east of the Allegheny Mountains. After years of delays the dam was completed in 1847, but by the 1850’s it was already rendered obsolete by the construction of a continuous rail route across the state. In 1857 the canal system and the Eastern Dam were sold to the Pennsylvania Railroad. The dam was intentionally notched in the winter of 1882, preventing a deep lake from reforming. Had this not been done, calculations reveal the dam would have failed in the great storm of 1889 causing a catastrophic flood, likely destroying the low-lying parts of Williamsburg 21 km downstream. The embankment of this dam still exists on private ground south of Hollidaysburg as a monument to engineering skills in the mid-1800’s. “There is nothing new except what is forgotten.” Mademoiselle Bertin, milliner to Marie Antoinette

Investigation by the ASCE Committee (Francis et al. 1891) and the Fate of their Report

A committee of four ASCE members visited the South Fork dam, took measurements, interviewed residents, and wrote a detailed report. Their state-of-the-art report was completed seven months after the disaster but was then sealed. Its publication was prevented or delayed by three Presidents of ASCE: Max Becker, William Shinn, and Octave Chanute. They were mainly railroad and steel men. Shinn was a former managing partner of Andrew Carnegie at the Edgar Thompson works - the investigation report remained sealed for his entire term as President. Chanute is best remembered today for his innovative research in aeronautics and later association with the Wright brothers. Five months into Chanute’s term, and two years after the flood, the long-awaited investigation report became public during the Chattanooga Convention in 1891. But three of the committee members stayed away, leaving James Francis alone to present the report.