FLOOD11725

• Designation Number: 87
• County: Garfield
• Community: Garfield County and Unincorporated Areas
• Basin: Colorado Mainstem
• Title: FIS - Garfield County and Unincorporated Areas
• Date: 2/1/1977
• Designation Date: 11/15/1978
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

Average Difference Between
10- and lOa-year Floods

Variation

Less than 2 feet
2 to 7 feet

0.5 foot
1. 0 foot

Seven reaches meeting the above' criteria ,,,,ere required for the
flooding sources of Garfield County. These included two for the
Colorado River (one at Rifle and one at New Castle), one each for
Alkali Creek and Cattle Creek, and three for the Roaring Fork River
(one at Cattle Creek Station and two at Carbondale). The locations
of the reaches are shown on the Flood Profiles (Exhibit l).

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5.2 Flood Hazard Factors

The Flood Hazard Factor (FHF) is the Federal Insurance Administra-
tion device used to correlate flood infor.mation with insurance rate
tables. Correlations between property da:mage from 'floods and their
FHF are used to set actuarial insurance premium rate tables based
on FHFs from 005 to 200.

The FHF for a reach is the average weighted difference between the
lO- and lOa-year flood water-surface elevations expressed to the
nearest one-half foot, and shown as a three-digit code. For example,
if the difference between water-surface elevations of the lO- and
lOa-year floods is 0.7 foot, the FHF is 005; if the difference is
l.4 feet, the FHF is Ol5; if the difference is 5.0 feet, the FHF is
050. When the difference between the lO- and lOO-year water-
surface elevations is greater than lO.O feet, accuracy for the FHF
is to the nearest foot.

5.3 Flood Insurance Zones

After the determination of reaches and their respective Flood
Hazard Factors, the entire unincorporated area of Garfield County
was divided into zones, each having a specific flood potential or
hazard. Each zone was assigned one of the following flood insur-
ance zone designations:

Zone A:

Special flood hazard areas inundated by
the lOa-year flood, determined by,
approximate methods; no base flood
elevations shown or Flood Hazard Factors
determined.

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Zone AO:

Special flood hazard areas inundated by
types of lOO-year shallow flooding where
depths are be1:ween l.O and 3.0 feet;
no Flood Hazard Factors determined.

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