National Weather Service United States Department of Commerce

Heavy Rainfall and Severe Thunderstorm Threats for the Plains and Southeast

A frontal boundary extending from the western High Plains to the Southeast will focus additional showers and thunderstorms this weekend. Some of these storms may become severe, alongside frequent lightning, and isolated instances of flash flooding. Meanwhile dry conditions will continue for the Great Basin where fire weather concerns linger. For the mid-Atlantic and Northeast, seasonable weather. Read More >

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COMMON HYDROLOGIC TERMS AND DEFINITIONS

BANKFULL: An established river stage/elevation at a given location along a river which is intended to represent the maximum safe water level that will not overflow the river banks or cause any significant damage within the river reach.

 

BASIN: Whole geographic area having a common outlet (such as a river, stream, or lake) for its surface runoff. Also known as drainage area or watershed.

CREST: The highest stage or level of water at a specific point before the water begins to recede.

FLOOD FREQUENCY: The chances that a particular flood event will occur during any given year. The greater the flood, the higher the "Year Flood" Value, but the less chance of occurrence. (i.e. a "100 Year Flood" has a 1% chance of occuring each year).

FLOOD STAGE: The elevation at which overflow of the natural banks of a waterway begins to cause damage or presents a flood-damage hazard near the gage where the elevation is measured (can also be expressed in terms of flood flow).

FLOW: The volume of water that passes through a point of a river during a given time. Usually expressed in cubic feet per second (cfs).

HYDROGRAPH: A graph showing stage, discharge, or other property of a river with respect to time.

REACH: The length of area between two specific points (usually between 2 gages) along a river, stream, or channel.

RUNOFF: The part of precipitation that flows toward a river or stream on the surface of the ground, or through the soil before returning to the surface.

STAGE: The level of the surface of a river or lake above a predetermined base elevation (or "datum").

WATER YEAR: October 1 through September 30.