History of Flash flood in Timeline

A flash flood is a rapid and intense flooding event in low-lying areas, characterized by a short timescale (less than six hours) between the causative rainfall or event and the start of flooding. These floods can result from heavy rain associated with severe thunderstorms, hurricanes, or tropical storms, as well as meltwater from ice and snow. Additionally, flash floods may be triggered by the collapse of natural ice or debris dams or man-made structures like dams. The Johnstown Flood of 1889, caused by a dam failure, exemplifies the destructive potential of flash floods.

2005: U.S. National Weather Service flood fatalities report

In 2005, the U.S. National Weather Service reported that, using a national 30-year average, more people die yearly in floods, 127 on average, than by lightning (73), tornadoes (65), or hurricanes (16).

2006: Analysis of flash floods in the United States

Analysis of flash floods in the United States between 2006 and 2012 shows that injuries and fatalities are most likely in small, rural catchments, that the shortest events are also the most dangerous, that the hazards are greatest after nightfall, and that a very high fraction of injuries and fatalities involve vehicles.

2012: Analysis of flash floods in the United States

September 2015: Utah cloudburst causes flash flood fatalities

In September 2015, a cloudburst in southern Utah resulted in 20 flash flood fatalities, with seven occurring at Zion National Park when hikers were trapped by floodwaters in a slot canyon.

2020: Impact severity scale proposed

In 2020, an impact severity scale is proposed providing a coherent overview of the flash flood effects through the classification of impact types and severity and mapping their spatial extent in a continuous way across the floodplain.