How are floods predicted?
Flood predictions require several types of data:
- The amount of rainfall occurring on a realtime basis.
- The rate of change in river stage on a realtime basis, which can help indicate the severity and immediacy of the threat.
- Knowledge about the type of storm producing the moisture, such as duration, intensity and areal extent, which can be valuable for determining possible severity of the flooding.
- Knowledge about the characteristics of a river's drainage basin, such as soil-moisture conditions, ground temperature, snowpack, topography, vegetation cover, and impermeable land area, which can help to predict how extensive and damaging a flood might become.
The National Weather Service (an agency within NOAA) collects and interprets rainfall data throughout the United States and issues flood watches and warnings as appropriate. They use statistical models that incorporate USGS streamflow data to try to predict the results of expected storms.
The USGS maintains a network of streamflow-gaging stations throughout the country.
Related Content
What is a 1,000-year flood?
Why do the values for the 100-year flood seem to change with every flood?
Does an increase in the 100-year flood estimate originate from climate or land-use change?
How can a 1,000-year rainfall not result in a 1,000-year flood?
We had a "100-year flood" two years in a row. How can that be?
Where can I find flood maps?
What are the two types of floods?
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Transcript and captions available soon.
What is a "500 year flood", and how do scientists determine if a flood is considered a "500 year flood"?
Listen to hear the answer.
Two 500-Year Floods Within 15 Years?
We talk to Bob Holmes about some of the recent flooding events occuring in the Midwest, how does a 500-year flood occur twice in 15 years, and what do the recent events have in store for folks downriver.
We had a "100-year flood" two years in a row. How can that be?
Listen to hear the answer.