FLOOD07888

• Designation Number: 327
• County: Adams
• Community: Unincorporated Adams County
• Basin: South Platte
• Title: FIS - Adams County, Colorado, Unincorporated Areas
• Date: 12/15/1989
• Designation Date: 9/1/1992
• Floodplain - Doc Type: Floodplain Report/Masterplan

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5.0 INSURANCE APPLICATION

In order to establish actuarial insurancli rates, the Federal Insurance
Administration has developed a process to transform the data from the
engineering study into flood insurance .crheria. This process includes
the determination of reaches, Flood Hazard Factors, and flood insurance
zone designations for each flooding sourc;estudied in detail affecting
the unincorporated areas of Adams County.

5.1 Reach Determinations

Reaches are defined as lengths of \<atercourses having relatively

the same flood hazard, based. on the 'average
water-surface elevations between the 110- and
difference does not have a variationigreater
the following table for more than 20 percent

weighted difference in
100-year floods. This
than that indicated in
of the reach:

Average Difference Between
10- and 100-Year Floods

Variation

Less than 2 feet
2 to 7 feet

0.5 foot
1. 0 foot

Seventeen reaches meeting the abovelcriteria were required for the
flooding sources studied in Adams I County. These included four
reaches for the South Platte River, ,three reaches each for Big Dry
and Little Dry Creeks, two reaches for Comanche Creek, and one
reach each for Little Comanche, Niver, Box Elder Creeks, and
Northfield Creek. (Downstream oB Devonshire Boulevard) and
Northfie1d Creek (Upstream of Devon~hire Boulevard).

5.2 Flood Hazard Factors

The Flood Hazard Factor (FHF) is the Federal Insurance
Administration device used to cotrelate flood information with
insurance rate tables. Correlatio,!s between property damage from
floods and their FHF are used to ~et actuarial insurance premium
rate tables based on FHFs fom 005 t6 200.

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The FHF for. a reach is the average Iweighted difference between the
10- and 100-year flood water-sl.1rfaice elevations expressed to the
nearest one half foot, and showni as a three-digit code. For
example, if the difference between [the water-surface elevations of
the 10- and 100-year floods is 0.1 foot, the FHF is 005; if the
difference is 1.4 feet, the FHF i~ 015; if the difference is 5.0
feet, the FHF is 050. When the difference between the 10- and 100-
year flood water-surface elevatio~s is greater than 10.0 feet,
accuracy for the FHF is to the near~st foot.
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