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Flood Terminology Explained!

By weather wktv

The following guide should help you during the Spring, Summer and Fall when flooding is most common. Flooding can occur because of heavy rain from a thunderstorm, a prolonged period of heavy rain, ice buildup on streams, creeks and rivers, snowmelt, etc. etc. Often times you hear terminology tossed around like watches, warnings, advisories, flash flooding, etc. All of them have their own meanings, and this should be a good reference to help you understand what those meanings are. Feel free to bookmark this link and save it for future reference.

Flood- An overflow of water that inundates areas and threatens damage.

Flash Flood- Rapid rise in water on a stream or creek or river, or a rapid movement of water into a normally dry area. Usually issued when most of the precipitation is forecast to fall in a 6 hour period.


National Weather Service Statement Definitions

Flood Watch/Flash Flood Watch- Issued when the forecast suggests the potential for flooding or flash flooding, but that flooding is not imminent or occurring.

Flood Warning/Flash Flood Warning- Issued when flooding or flash flooding is imminent or in-progress...requires immediate action in the affected areas.

Urban and Small Stream Flood Advisory- Issued when flooding of small streams, creeks and poor drainage flooding in urban areas is occurring, but damage would be minor and most problems would be minor inconveniences.

Flood Advisory- Issued when minor flooding along a river or stream or creek is ongoing, but with little to no damage or threat to life and property.

Flood Statement- A statement issued by the National Weather Service to provide an update to a prior warning.


Terms Relating to Degrees of Flooding

Action Stage- The point where a river reaches a level that borders on criteria for flooding, but is not actually causing flooding. Normally a warning will be issued at this point as a precaution.

Flood Stage- The point where a river's water level begins overflowing its banks.  

Minor Flooding- The point where a river's water level begins to overflow into populated areas, causing little or no damage, but possibly some inconveniences.

Moderate Flooding- The point where a river's water level overflows into populated areas, potentially causing some minor damage and some evacuations.

Major Flooding- The point where a river's water level causes extensive flooding with significant damage and/or evacuations.


Other Useful Flooding Terms

Bankfull Level- The point at which water in a river, stream or creek fills up the banks, but is not enough to cause flooding.

Breakup Jam- An ice jam that is caused by the breaking up of ice. Usually leads to some flooding.

Crest- The point at which a river, stream or creek is flooding and at its highest level.

Discharge- How fast the water in a stream, creek or river is moving.

Flood of Record- The highest recorded water level on a body of water.

Flood Plain- The area of a river valley that has been inundated by floods in the past.

Gage- An instrument that measures the flow and level of a river, stream or creek.

Headwaters- Streams and creeks at the source (beginning) of a river.

Hydrograph- A chart that shows water level and flow information about a river, stream or creek.

Ice Jam- A build up of ice on a river, stream or creek that prevents water from flowing.

Main Stem River- The larger rivers in an area, usually fed by numerous small streams or creeks.

QPF- Quantative Precipitation Forecast...aka how much rain is forecasted to fall.

## Year Flood- A term used to describe a flood that occurs once every ## years.

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