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The fury of floods

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July 20th, 2018
These images show the massive damage the flood caused in Johnstown. Over 2,200 people lost their lives.

These images show the massive damage the flood caused in Johnstown. Over 2,200 people lost their lives.

The last several months have been some of the rainiest on record for many parts of the United States. Both flash and full-blown river floods have occurred in states from Texas and Michigan to Pennsylvania and, perhaps most notably, Ellicott City, Md.

The latter town broke ground more than 200 years ago along a narrow stretch of the Patapsco River. Historically a flood hazard given its immediate proximity to a low-banked tributary and multiple inclined roads that feed into a central area, the small city is a magnet for rushing water.

In July 2016, a thunderstorm dumped an estimated half-foot of rain in two hours, eviscerating its touristy Main Street. Less than two years later, another storm dropped eight inches of rain in two hours, ravaging the newly repaired thoroughfare and causing millions of dollars in damage.

But not all floods are due to location alone. In fact, two of the worst flood disasters in modern American history were a combination of factors involving dams.

The Johnstown, Pa., flood

Situated beside a confluence of the Little Conemaugh and Stony Creek Rivers, Johnstown was a thriving community. By the late nineteenth century, the canal, iron, and railroad industries had drawn 30,000 residents to the village.

Due to the region’s mountainous topography, most of the town’s construction occurred close to the rivers. These waterways grew even narrower as developers, in an attempt to add building space, used slag from the local steel mills to artificially extend the river banks.

This was a problem during heavy rain; perhaps more damaging, though, were the actions of steel mogul Henry Clay Frick.

A close and wealthy associate of industrialist Andrew Carnegie, Frick, along with a group of investors, selected the nearby South Fork Dam as a private country retreat for their rich counterparts.

Completed in 1853 in conjunction with the Pennsylvania Main Line canal, the dam was 93 feet wide and 72 feet high. The state soon abandoned the structure, however, which was originally built for a reservoir for the canal basin in Johnstown.

In 1881, Frick and his investors altered the dam to create a 400-acre lake attached to their exclusive South Fork Fishing and Hunting Club. The modifications included the removal of discharge pipes that permitted the controlled release of water; they lowered the dam’s top to make way for a carriage path; and they installed fishnets, which trapped debris and impeded water flow.

On May 31, 1889, after days of heavy rainfall, the dam failed.

The structure broke at 2:55 p.m., unleashing 20 million tons of water (roughly 380 times heavier than the Titanic) onto Johnstown. In the end, 2,209 people perished in the flood—in this case, a preventable tragedy.

The St. Francis Dam, Southern California

In 1926, another dam opened for business; this one, a curved concrete gravity dam at a reservoir for nearby Los Angeles. At first, the city got its water through a series of ditches fed by the Los Angeles River.

In 1913, L.A.’s water department completed construction on a 233-mile aqueduct. To guard against water and power loss due to earthquakes or drought, the city built a second source about 40 miles away in the San Francisquito Canyon.

The St. Francis Dam was 170 feet wide at the base and 205 feet high from its foundation. Water department engineers, under the leadership of General Manager William Mulholland, had built a solid dam, save for a single element that led to a catastrophic failure.

Just before midnight on March 12, 1928, Mulholland’s magnificent dam failed. According to one witness anecdote, there was no moon, and the sky was overcast with an eerie fog.

At 11:58 p.m., the St. Francis Dam collapsed, spilling enough water to sustain Los Angeles for two years.

The initial wave was 140 feet high (the equivalent of a 14-story building) and moved through the canyon at 18 miles per hour. The dam keeper and his family were likely the only witnesses to the actual collapse; of course, none of them lived to tell the tale.

But one man who worked for the water department did make it, and he later recalled what happened to him.

“We were all asleep in our wood-framed home in a small canyon just above the powerhouse. I [heard] a roaring like a cyclone,” remembered Ray Rising, one of only three people in his small adjacent community to survive.

“The house disintegrated. In the darkness, I became tangled with an oak tree, fought clear and swam to the surface … I grabbed the roof of another house, jumping off when it floated to the hillside.”

While estimates vary, as many as 600 people were not so fortunate. The rushing water ripped through 50 miles of Southern California before emptying into the Pacific Ocean.

The cause—the remnants of an ancient landslide on the dam’s building site. According to engineers today, there’s no way Mulholland had the technology to detect such instability in the 1920s.

The St. Francis Dam flood was a combination of natural fury and human ignorance.

All the same, humankind soldiers on and will continue to do so. That said, we should venture into the future with a healthy respect for Mother Nature.

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