Dangerous flash floods sparked evacuations and are responsible for at least one death in parts of New York early this week, roughly one year after flash floods surprised the desert entertainment mecca of Las Vegas.
According to the National Weather Service, a flash flood is a flood caused by heavy or excessive rainfall in a short period, generally less than six hours. Flash floods are usually characterized by raging torrents after heavy rains that rip through river beds, urban streets or mountain canyons, sweeping along everything in their path. They can occur within minutes or a few hours of excessive rainfall.
Plus, this summer, the early arrival of an expected El Niño ocean weather phenomenon is adding to heat and other weather extremes, which can mean more water in places.In New York, Gov. Kathy Hochul declared a state of emergency Sunday for Orange County, about 60 miles north of New York City, where about 8 inches of rain poured down in a short time. She later extended the state of emergency to Ontario County in western New York, southeast of Rochester.
Flash floods can also occur even if no rain has fallen, such as after a levee or dam has failed, or after a sudden release of water by a debris or ice jam. What’s more, the inability of some municipal storm sewers to keep up with the water removal can aggravate the situation, and that’s been especially true as the nation’s infrastructure has aged.
Flash flooding is expected to increase Most worrying, perhaps, is that flash flooding is expected to increase as there are more extreme precipitation events brought on by climate change and man-made atmospheric warming, meteorologists and climate scientists say. This is because warmer temperatures increase evaporation, which puts more moisture into the atmosphere that then gets released as rain or snowfall.