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What is a 1,000-year flood?
The term “1000-year flood” means that, statistically speaking, a flood of that magnitude (or greater) has a 1 in 1000 chance of occurring in any given year. In terms of probability, the 1000-year flood has a 0.1% chance of happening in any given year.
These statistical values are based on observed data.
Learn About USGS Hazards Science and More About National Preparedness Month: The very nature of natural hazards means that they have the potential to impact a majority of Americans every year. USGS science provides part of the foundation for emergency preparedness whenever and wherever disaster strikes.
The number of major floods in natural rivers across Europe and North America has not increased overall during the past 80 years, a recent study has concluded. Instead researchers found that the occurrence of major flooding in North America and Europe often varies with North Atlantic Ocean temperature patterns.
Atmospheric rivers are a global weather phenomenon that can bring large amounts of rain or snow to the U.S. West Coast each year. These rivers of wet air form over the Pacific Ocean near Hawaiʻi and pick up large amounts of moisture from the tropics and on their way to the West Coast. This moisture is carried in narrow bands across the Pacific Ocean to California, Oregon, Washington and Nevada.
Some regional trends; no widespread national pattern
Flooding costs the United States more than $7 billion per year and claims more than 90 lives annually. During the Spring and Summer of 2011, the central U.S. experienced epic flooding, while Hurricane Irene followed by Tropical Storm Lee caused severe flooding in the east and northeastern U.S, setting numerous flood records at USGS streamgages. Dr. Robert Holmes discusses...
Gagehouse at 06225500 Wind River near Crowheart WY right before it washed away.
Jul 01 2011; 13,900 ft3/s
Whether you drink water from your tap, use electricity or canoe down your local river, chances are you benefit from USGS streamgage information. So what is a streamgage and what does it do for you? This CoreCast episode gives you the inside scoop on your silent superhero.
Transcript and captions available soon.
Interview with USGS crews regarding the 2009 flooding events in Fargo, ND.
Understanding the forces that influence major floods can help inform the design of more resilient infrastructure. Image shows a major flood on the St. John River on the border of Maine, United States and New Brunswick, Canada, April 29, 2008. This site was part of the study. USGS Public Domain.
A photo of floodwaters reaching up to a street sign in Texas.
A USGS crew prepares to measure Hurricane Harvey floodwaters off of a bridge. Photo by Cassi Crow, USGS.