What are the two types of floods?
There are two basic types of floods: flash floods and the more widespread river floods. Flash floods generally cause greater loss of life and river floods generally cause greater loss of property.
A flash flood occurs when runoff from excessive rainfall causes a rapid rise in the water height (stage) of a stream or normally-dry channel. Flash floods are more common in areas with a dry climate and rocky terrain because lack of soil or vegetation allows torrential rains to flow overland rather than infiltrate into the ground.
River flooding is generally more common for larger rivers in areas with a wetter climate, when excessive runoff from longer-lasting rainstorms and sometimes from melting snow causes a slower water-level rise over a larger area. Floods also can be caused by ice jams on a river or high tides, but most floods can be linked to a storm of some kind.
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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?
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Guidelines for determining flood flow frequency—Bulletin 17C
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Identifying and preserving high-water mark data
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No abstract available.
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Flooded roadway in Maryland
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