|Date||March 17, 1936 to March 18, 1936|
|Location||Johnstown, Pennsylvania area|
|Property damage||US$43 million|
The Johnstown flood of 1936, also collectively with other areas referred to as the Saint Patrick's Day Flood, was a devastating flood in Cambria County, and Johnstown, Pennsylvania proper, referred to as "Greater Johnstown".
The flood was preceded by rains from March 9 that did not stop until March 22, 1936. The storms brought warmer 50 °F (10 °C) weather that was a cause of one stage of flooding and the continuous rains a second cause of flooding. The natural run-off of 1 to 3 inches (2.5 to 7.5 cm) was far surpassed by the deluge of from 10 to 30 inches (25 to 75 cm) of water in the region. The flood came before pending flood control legislation was enacted or any significant flood control measures implemented. The narrowness of the valleys and encroachment of buildings on the river banks contributed to record flooding. By the time nightfall came one-third of the city was under 17 feet (5.2 m) of water and by the time flooding was over twenty-five people lost their lives. The damages, estimated at $43 million, made it the worst flood since the flood of 1889 and the event is chronicled at the Johnstown Flood Museum
After the flood, sweeping nationwide flood control laws were enacted and from 1938 to 1943 Johnstown saw many projects completed. These measures gave the people the feeling that the area was now "flood free", and it was touted as such until the flood of 1977.
On June 7, 1906, Johnstown experienced major flooding that reached 17 feet (5.2 m) on the Franklin street bridge. On March 14, 1907, there was flooding that was bested only by the one in 1898. There was talk of flood control but nothing was accomplished. Talks had finally determined that something needed to be done and the legislature was working on a bill by 1935. On March 15 and 16 heavy rains hit the Johnstown area. Warmer weather began to melt the accumulated snow on the ground, and the soil became saturated. By March 17, the Conemaugh River reached flood stage and was continuing to rise at the rate of 18 inches per hour. The raging streams merged and entered Johnstown. At Locust Street and Lee Place, the flood crest reached to within five feet of the high-water mark of the catastrophic flood of May 31, 1889. In the section known as Cambria City, the stone bridge, unlike in 1889, remained unobstructed, resulting in a flood level here that was 18 inches higher than that of the 1889 flood.
On March 18, whistles and sirens began to scream, as word spread that the Quemahoning Reservoir dam had broken. People rushed for higher ground. This report turned out to be false and people started making their way back into town. Robert Bondy, the American Red Cross national director of disaster relief arrived to start relief efforts. The Works Progress Administration sent 7000 men and 350 to report to Mayor Shields. 1724 enlisted and 114 officers were mobilized by Governor George H. Earle effectively placing the area under martial law. 80 members of the Highway Patrol and 81 members of the State Police (These two were merged on June 29, 1937.) arrived to help restore and maintain order. The gauge on the Poplar Street Bridge showed 15 feet above flood level and the 14 feet above flood stage at the "Point".
As the flood was rising people crossed the Inclined Plane Bridge and were ferried to the Westmont hilltop by the funicular inclined plane, that only stopped when the flood waters rose too high for it to continue operating.
A storm front moved into Pennsylvania that brought 50 °F (10 °C) weather. This melted the accumulated snow in the mountains, and was accompanied by three days of severe rains. The land was already saturated causing the swift run-off to converge on the major streams and rivers eventually heading into Johnstown.
The storms brought warmer 50 °F (10 °C) weather that was a cause of one stage of flooding and the continuous rains a second cause of flooding. The natural run-off of 1 to 3 inches (2.5 to 7.5 cm) was far surpassed by the deluge of from 10 to 30 inches (25 to 75 cm) of water in the region. The Connecticut River at Hartford, Connecticut, was 8.6 higher that recorded in 300 years, the Susquehanna River at Harrisburg, was 3.5 feet higher than seen in 200 years, and the Ohio River at Pittsburgh was 6.1 feet higher than ever seen since 1762, and flooding was wide spread.
The Pennsylvania General Assembly passed an emergency temporary 10% alcohol tax, intended to help with clean up, recovery, and to assist flood victims. In 1963 it was raised to 15% and in 1968 it was raised to 18%.
By 1942 around $41 million had been collected and as of 2010 the tax was still active bringing in approximately $15.4 billion since inception. Efforts to repeal the tax has met continued opposition from opponents, such as unions workers employed by the Pennsylvania Liquor Control Board, that have successfully fought to keep the tax and prevent the privatizing of the state run liquor business.
Flood control measures had been introduced, but had bogged down in legislative debates. The Johnstown flood of March, 1936 came before anything significant had been accomplished. The 1936 Johnstown flood was the seminal event that gave modern federal flood control measures in the United States their impetus. 15,000 letters were sent to President Franklin Delano Roosevelt asking for help. The Johnstown Tribune and Democrat (which later merged with The Tribune-Democrat) demanded federal aid. Senators and Representatives in Washington, D.C. enacted the Flood Control Act of 1936 and the Flood Control Act of 1937. In August, 1938 work began on the most extensive flood control channel improvement project in American history. On November 27, 1943, Colonel Gilbert Van B. Wilkes, Chief of the US Army Corps of Engineers, Pittsburgh District reported to Johnstown leaders that the flood problem had been effectively solved. Johnstown began to promote the city as "Flood Free".