Natural disasters such as hurricanes and tornadoes are unavoidable. Man-made disasters are not. Sometimes one can lead to the other, as in the case of poorly maintained levees breaking, creating flooding in the wake of hurricanes. Massive mudslides are often the result of a combination of the forces of nature and poor engineering and design on the part of man. Dams have collapsed because of errors of engineering leading to massive, sudden floods and the deaths of hundreds, as in the case of the collapse of the St. Francis Dam in Los Angeles. Some failures are simply errors of judgment.
Accidents also occur when the engineering was sound but deficiencies in materials used in construction or maintenance of man-made structures causes them to fail. Over time, many bridges have collapsed because of the failure of seemingly minor parts, which led to a failure chain causing them break apart. Others have been swept away when they were unable to resist the forces of water rushing at or near flood levels. Over 10% of the bridges in the United States were rated as structurally deficient in the early 21st century, meaning that they require higher levels of monitoring and preventive maintenance in order to avoid them becoming another disaster of the type described here.
Here are ten times when judgement, engineering, or design have lead to failures.
The Johnstown Flood
The collapse of the South Fork Dam on May 31, 1889 led to the Johnstown flood. The dam failed, releasing Lake Conemaugh to sweep through the valley where Johnstown stood, destroying much of the town and killing over 2,000 people, most of whom had little warning. Although the dam failed after several days of heavy rains, years of poor maintenance and an inadequate design of the structure were the causes of the disaster. The dam was built by the Commonwealth of Pennsylvania as part of the canal system between 1838 and 1853, but after railroads made the canals obsolete, the dam and the lake it created, Lake Conemaugh, were sold.
The purchasers were a consortium led by Pittsburgh businessmen, including Henry Clay Frick, which bought the property to create a private resort which they called the South Fork Fishing and Hunting Club. They made alterations to the dam, lowered and widened its top, installed screens in the spillway to prevent fish from leaving the lake via the spillway, and ignored the previously removed drain pipes and valves. They thus had no means of lowering the water levels of the lake. The road built on the top of the dam was to provide access to the club. After the modifications the dam was reported to be leaking in several locations. Leaks were repaired with a mixture of mud and straw.
After several days of heavy rain in late May 1889, the level of water in the lake was threatening to crest the top of the dam, and it was leaking heavily in several places. On May 31 the president of the South Fork Club mustered a group of maintenance workers and attempted to relieve pressure on the dam by opening the spillway. The screens which had been placed there to trap fish were admirably suited to also trap debris, and the spillway was hopelessly clogged. Others attempted to raise the crest of the dam by piling rocks and mud on top. In Johnstown, about 14 miles below the dam, water levels in the streets reached as high as ten feet in some places as the Little Conemaugh overflowed its banks.
High water in the streets trapped many residents in their homes, on the upper floors. They were huddled there when the dam broke before the pressure of the water just before 3 PM. As the water rushed towards Johnstown it created and gathered debris which swept along with it, including the remains of a railroad bridge which had stopped the flood for a few minutes. The wall of water and debris hit Johnstown about one hour after breaching the dam, the same amount of time it took Lake Conemaugh to drain. It carried the remains of some small towns, railroad cars, trees, dead horses and humans, and coils of barbed wire which it acquired when it crushed the Cambria Iron Works.
The relief effort after the disaster at Johnstown continued for years and is a story of its own. Although the dam had not been properly maintained for years and it had been modified from its original design, an investigation concluded that it would have failed anyway, faulting the original designers. This investigation, by the American Society of Civil Engineers (ASCE) was challenged in the 21st century, when another investigation concluded that it was the modifications to the dam which led to its failure, particularly the failure to maintain the spillway. None of the survivors or their families ever received any compensation from the South Fork Hunting and Fishing club for their losses.