FLOOD07643

• County: Statewide
• Basin: Statewide
• Title: Physical and Economic Feasibility of Nonstructural Flood Plain Management Measures
• Date: 3/1/1978
• Prepared For: US
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

Greater valued structures are likely to require additional iands.cape and aesthetic work to make
them compatible with the site. In thh situation, increased costs may be offset by increased value
and the percentage may not be too different.

TABLE 4-1

ESTIMATED COST TO RAISE AN EXISTING STRUCTURE IN-PLACE'

Item

Estimated Cost

Brace and Load Structure
. Disconnect, reconnect utilities

$3,200.

Extend Existing Foundation

Reconstruct Porches, Ramps and Stairs,
Relandscape

2,500.

Total First Cost

=

2,050.
$7,750.
$ 621.
2.1

Annual Cost'

Annual Cost as Percent of
Structu re Val ue

=

=

, Estimated for a 1,600 square foot, $30,000 structure without basement, on raised foundation.
Height raised assumed to be 3 feet. Costs include 25 percent for contractor's bonds, overhead,
profit, and engineering.
2 Amortized at 7 percent for 30 years.

Economic Feasibility
Raising a structure without basement reduces damage caused by flood events below the
raised first floor elevation. Residual damage still remains for flood events above the raised first
floor elevation and some minor damage may occur to the underside of the first floor flooring.
Analysis of damage reduced by raising a structure three feet and five feet was made in Appendix
A. Results of this analysis are presented in Figures 4-2 through 4-5. A structure was assumed to
be raised three and five feet for the conditions indicated and zero damage was assumed to
occur below the first floor. Damage reduced was computed as the difference in expected
annual damage with and without the structure raised. The curves show considerable variability
depending on the type structure and event at the first floor.

An estimate of economic feasibility was made by plotting the estimated cost of raising a
structure three feet and five feet on the respective Figures.

The estimated minimum cost for raising a structure three feet was 2.1 percent from Table 4-1.
It was assumed the cost to raise a structure five feet would be 25 percent more or approximately
2.6 percent. When compared with expected annual damage reduced these data indicate that for
one story, no basement structures, raising a structure three feet or five feet is generally feasible
below the 10 year flood plain, not likely to be feasible above the 15 year flood plain, and

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