FLOOD04455

• County: Statewide
• Community: State of Minnesota
• Basin: Statewide
• Title: Flood-Proofing Administrative Manual for Minnesota
• Date: 1/1/1997
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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C. APPLICATIONS OF FLOOD-PROOFING

GENERAL LIMITATIONS

Although flood-proofing can be used as an effective means of flood damage
reduction..particularly in the case of industrial or large commercial
structures, problems may be encountered that limit both its practicality
and desirability. Frame structures, for instance, seldom have sufficient
soundness to allow flood-proofing. Costs may prove excessive and could
prove to be a deterrent to its use.

In many cases, flood-proofed structures may not be accessible during periods
of flooding and a rapid rise of floodwater may preclude the safe evacuation
of persons. Further, persons who attempt to gain access to these structures
may be subjected to serious hazards. Floodwater velocities over three feet
per second at depths greater than two feet are considered dangerous for
pedestrian travel. In areas of long duration flooding, lack of access to,
or the need for evacuation of residences or other structures can place a
severe economic burden on both the individual and the community. This may
be particularly true where commercial and industrial firms are forced to
close with attendant loss of ' jobs and profits.

For many flood-proofing measures, varying degrees of human intervention may
be required to complete protective procedures. In some areas where. floods
are of a "flashy" nature, it may be considered unsafe to depend on any human
intervention, however little.

Finally, flood-proofed structures should not be considered immune from flood
damage. Faulty materials or improper design and/or improper installation or
construction may result in failure of the structure. Floods of a magnitude
greater than the regulatory flood may exceed the capabilities of the flood-
proofing measures. Thus careful and thorough consideration must be given to
the design and construction of flood-proofed structures.

Most zoning ordinances require that the finished surface of the basement
floor, or the first floor if there is no basement, be placed on fill at or
above the regulatory flood datum (RFD). For large industrial structures, and
for residences on small lots, it may be impractical to comply strictly with
the fill requirements. and other flood-proofing measures may be authorized.
However, considering cost, access to the structure, and reliability, elevation
on fill should always be the preferred method of minimizing flood damage.
Structures elevated on fill require no human intervention to activate flood-
proofing devices, are not subject to damage resulting from direct contact with
flood waters, and are easily accessible if the fill is contiguous with high
ground. Where structures are elevated on fill, good engineering practices

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