Flood: An overflow of water onto normally dry land. The
inundation of a normally dry area caused by rising water in an existing
waterway, such as a river, stream, or drainage ditch. Ponding of water
at or near the point where the rain fell. Flooding is a longer term
event than flash flooding: it may last days or weeks.
Flash flood: A flood caused by heavy or excessive
rainfall in a short period of time, generally less than 6 hours. Flash
floods are usually characterized by raging torrents after heavy rains
that rip through river beds, urban streets, or mountain canyons sweeping
everything before them. They can occur within minutes or a few hours of
excessive rainfall. They can also occur even if no rain has fallen,
for instance after a levee or dam has failed, or after a sudden release
of water by a debris or ice jam.
Definitions and criteria from: NOAA, NWS |
