FLOOD04322

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Benefit-Cost Analysis for Urban Drainage Planning
• Date: 3/1/1974
• Prepared For: UDFCD
• Prepared By: CSU
• Floodplain - Doc Type: Educational/Technical/Reference Information

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floodplain can then be divided into areas of equal flood depth,

i.e. 0-2 ft., 2-4 ft., and 4+ ft. Flood damages are then found

by planimetering these areas and applying the per acre damage

factors. The per acre damage ~actors can be computed by

estimating typical exposure for each damage category and apply

ing the individual damage factors. Table 3 summarizes the pro-

cedure for obtaining area damage factors for 3 and 4 ft. flood

depths for a sample low density residential area.

For existing areas that are not homogeneous with respect

to flood damage, a more detailed analysis must be performed.

For each damage category the value exposed to flooding must be

known. For example, estimation of the structural damage to a

particular residential unit requires knowledge of the value of

the structure. The exposure is multiplied by the damage factor

taken from the appropriate depth versus damage curve. Dollar

damage is estimated for each damage category, and tabulated by

reach as in Table 4.

Estimation of future flood damages for presently under-

developed areas will require the development of weighted per

acre flood damage factors. These factors should be weighted

to reflect the probable percentage that each land use will be

of the total undeveloped area. This information was obtained

or estimated in the hydrologic analysis, and an example is given

in Table 5.

~ Leonard Rice Consullmg Water Engmeers, Inc.