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Flood or Flooding

The purpose of this page is to define flood or flooding, commonly used terms in floodplain management.


A general and temporary condition of partial or complete inundation of normally dry land areas from:

(1) The overflow of inland or tidal waters;

(2) The unusual and rapid accumulation or runoff of surface waters from any source;

(3) Mudslides (i.e., mudflows) which are proximately caused by flooding and are akin to a river of liquid and flowing mud on the surfaces of normally dry land areas, as when earth is carried by a current of water and deposited along the path of the current.

A flood inundates a floodplain. Most floods fall into three major categories: riverine flooding, coastal flooding, and shallow flooding. Alluvial fan flooding is another type of flooding more common in the mountainous western states.

NFIP Requirement

59.1 - Definition


Related Keywords

Special Topic Resources

IS-9 Managing Floodplain Development Through The National Flood Insurance Program (NFIP)

  • Page 1-10, Coastal Flooding
  • Pages 1-17 and 6-30, Mudflow
  • Page 1-6, Riverine Flooding
  • Page 1-12, Shallow Flooding

Supplemental Information

Flood can also mean the collapse or subsidence of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in flooding as defined in the previous part of this definition.

Last Updated: 
03/27/2018 - 09:35