Hydrologic Terms

The following terms either ALERT hydrologic interests of flooding situations that may cause some inconvenience, or WARN hydrologic interests of flooding situations that may pose a threat to life and property.

PRODUCT Description
 FLOOD WATCH Indicates that flash flooding is a possibility in and close to the watch area. Those in the affected area are urged to be ready to take quick action if a flash flood warning is issued or flooding is observed. These watches are issued for rapid flooding that is expected to occur during or within 6 hours after heavy rain has ended.
FLASH FLOOD WARNING Issued for life/property threatening rapid flooding that occurs during or within 6 hours after heavy rain has ended. It could be issued for rural or urban areas as well as for small streams and creeks. The degree of flash flooding depends on local terrain, ground cover, degree of urbanization, amount of man-made changes to the natural river banks, and initial ground or river conditions. Dam breaks or ice jams can also create flash flooding.
URBAN AND SMALL STREAM FLOOD ADVISORY Alerts the public to flooding which is generally only an inconvenience and does not pose a threat to life and/or property. Issued when heavy rain will cause flooding of streets and low-lying places in urban areas, or if small rural or urban streams are expected to reach or exceed bankfull.
FLASH FLOOD STATEMENT Used as a follow-up to Flash Flood Warnings and Watches. The statement will contain the latest information on the event.
FLOOD WATCH Indicates that widespread flooding is a possibility in and close to the watch area. Those in the affected area are urged to be ready to take quick action if a flood warning is issued or flooding is observed. These watches are issued for general flooding that is expected to occur during or within 12 hours after heavy rain has ended.
FLOOD WARNING Issued for life/property threatening general flooding that occurs during or within 12 hours after heavy rainfall has ended. It could be issued for rural or urban areas as well as for areas along small streams and creeks.
FLOOD STATEMENT Used as a follow-up to Flood Warnings and Watches. The statement will contain the latest information on the event.
FLOOD POTENTIAL OUTLOOK Used to inform the public of the potential for heavy rain and/or large scale river flooding. Issued more than 12 hours in advance of a possible event.
FLOOD WARNING (RIVER) Used to inform the public of long-term (more than 12 hours) flooding along major streams and rivers, which is a threat to life and/or property. Usually contains river stage forecast and crest information, and the history and impact of the flood.
FLOOD STATEMENT (RIVER) Used to update and expand information in a river Flood Warning. May also be used in lieu of a Flood Warning if flooding is expected or imminent, but does not pose a threat to life and/or property.
RIVER STATEMENT Used to provide information about non-routine, non-flooding situations on main stem rivers.
RIVER SUMMARY Contains routine and forecast hydrological information, such as observed river readings, precipitation reports, and river forecasts.
RIVER RECREATION STATEMENT Commonly used to provide forecasts of the pool and outflow for various reservoirs across a Hydrologic Service Area.
 

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