As Elias Unger awoke on the morning of May 31, 1889, he noticed that a record overnight downpour had caused Lake Conemaugh to almost crest the South Fork Dam, located down the hill from his farmhouse in central Pennsylvania.
Unger, president of the South Fork Fishing and Hunting Club, rallied fellow members to assist him in reinforcing the face of the dam.
As the day progressed and the lake's waters continued to rise, the men realized the dam's failure was imminent. Telegraphs were sent to Johnstown, located 14 miles downstream, warning residents of the pending danger, though the messages were never passed to authorities due to previous false alarms.
By mid-day, Unger had ordered his club to higher ground, where they watched as 20 million tons of water roared from the lake down the Little Conemaugh River as the dam burst shortly after 3 p.m.
Researchers say the flood had a flow rate comparable to the Mississippi River as it rolled through the towns of South Fork, Mineral Point, East Conemaugh, Woodvale and Johnstown -- killing 2,209 and causing hundreds of millions of dollars in property and infrastructure damage.
At the time, it represented the largest single loss of civilian life in United States history, and in commemoration of the disaster, the Federal Emergency Management Agency (FEMA) declared May 31, 1999 to be National Dam Safety Awareness Day.
National Dam Safety Awareness Day has since become an annual event, and a number of state and federal agencies use it as an opportunity to educate the public about both the benefits of dams and the risks associated with potential dam incidents and failures.
Chief amongst those celebrating National Dam Safety Awareness Day is the Association of State Dam Safety Officials (ASDSO), which earlier this week announced the availability of a new guide, titled "Living With Dams: Know Your Risks".
A full list of other agencies and their dam safety awareness outreach efforts can be found on ASDSO's website here.
HydroWorld.com reported in March that the American Society of Civil Engineers (ASCE) had given the country's dams a "D" grade on its 2013 Report Card for America's Infrastructure.
For more dam safety news, visit here.