Flood Severity Definitions

Once a river reaches flood stage, the flood severity categories used by the National Weather Service (NWS) include minor flooding, moderate flooding, and major flooding. Each category has a definition based on property damage and public threat.

  • Minor Flooding - minimal or no property damage, but possibly some public threat or inconvenience
  • Moderate Flooding - some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations are necessary.
  • Major Flooding - extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.

The impacts and severity of flooding vary locally.  For each NWS river forecast location, flood stage and the associated severity categories are established in cooperation with public officials.  The impact and severity of flooding at a given stage is not necessarily the same at all locations along a river reach due to varying channel and bank characteristics, or the presence of levees on portions of the reach. 


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