Floodplain Protection Standards - What is a floodplain?

Before getting too far into the regulatory details of the floodplain program, it might be helpful to define exactly what a floodplain is.

Diagram showing the aspects of a floodplain.

The floodplain is that land which has been or may be covered by floodwater during the regional flood. The floodplain includes the floodway and floodfringe areas.

The floodway is the channel of a river or stream, and those portions of the floodplain adjoining the channel required to carry the regional flood discharge. The floodway is the most dangerous part of the floodplain -- it is associated with moving water.

The floodfringe is the portion of the floodplain outside of the floodway, which is covered by flood water during the regional flood. The term, "floodfringe" is generally associated with standing water rather than flowing water. It is also that part of the floodplain in which development is allowed subject to the floodplain development standards.

The regional flood is the same as the 100-year flood, the 1‰ chance flood, or the base flood (FEMA).

The regional flood elevation is the elevation determined to be representative of large floods known to have occurred in Wisconsin or which may be expected to occur on a particular lake, river, or stream at a frequency of 1‰ during any given year.

The flood protection elevation is an elevation which is 2 feet above the regional flood elevation.

For more information, contact:
Gary Heinrichs, Floodplain Planning Program Manager
(608) 266-3093