A flash flood in Oregon kills 324 people on this day in 1903. The sudden onslaught of water caused millions of dollars in damages to the central Oregon town of Heppner.
Nearly a tenth of the United States is made up of floodplains that would normally be inundated with water at least every 100 years without man-made control systems. In fact, most of the country's major cities are built on these floodplain areas, but dams, levees and floodways have been constructed to stave off regular flooding.
Damaging and deadly, a flash flood is more limited in scope than a regular flood, arising very quickly when torrential rains hit small streams or rivers with limited carrying capacity. The Heppner flood was an extreme example of a flash flood.
Before the flood, extremely hard rain and hail came down in the Blue Mountains, which rise above Heppner. Reports say that the storm may have lasted only an hour, but it overwhelmed the small streams of the area and caused a 20-foot wave of water to thunder through the town with little warning. About 200 people were simply swept away from the community. A third of the town was absolutely destroyed. The flood also wreaked havoc on surrounding farms, killing another 125 people.
The largest and most violent flood on record was not witnessed by any people. Occurring during the last Ice Age, an ice dam located in modern-day Montana broke and, for about the next 11 days, a volume of water equivalent to five times what is contained in Lake Erie rushed over Idaho and eastern Washington. It scoured the landscape and scraped everything down to bedrock for hundreds of miles.