FLOOD04875

• County: Weld
• Community: Eaton
• Basin: South Platte
• Title: FIS - Eaton
• Date: 9/22/1999
• Prepared For: Eaton
• Prepared By: FEMA
• Floodplain - Doc Type: Current FEMA Regulatory Floodplain Information

The flood elevation differences, FHFs,
base flood elevations for each flooding
the county are summarized in Table 3.

f load insurance zones, and
SOurce studied in detail in

5.4 Flood Insurance Rate Map Description

The Flood Insurance Rate Map for the unincorporated areas of Weld
County is, for insurance purposes, the principal result of the
Flood Insurance Study. This map (published separately) contains
the official delineation of flood insurance zones and base flood
elevation lines. Base flood elevation lines show the locations of
the expected whole-foot water-surface elevations of the base (100-
year) flood. This map is developed in accordance with the latest
flood insurance map preparation guidelines published by FEMA.

6.0 OTHER STUDIES

The COE published the Special Flood Hazard Information Report. South
Platte River, Volume I, April 1977 (Reference 5), which is a study of
the South Platte River in Weld County, to compare the 1973 flood with
the lOa-year flood. The information provided varies from stage-
discharge relationships at each cross section in the rural areas to
water-surface profiles in the urban areas. The profiles in this report
differ from the COE profiles by more than 0.5 foot in a few places. At
cross section E, the COE did not consider the skew of the bridge, which
causes increased effective pier widths and higher elevations.
Additional cross sections taken below Cross Section I for this report
indicated that the lOa-year flood would be confined by levees, thus
raising the water surface above that computed by the COE. At U.S.
Highway 85, the COE considered the Latham Ditch as carrying part of the
lOa-year flow. As this is not considered by FEMA policy, the elevations
in this report are higher than the COE computed elevations.

The COE completed a Flood Plain Information report on the Cache La
Poudre River at the City of Greeley in March 1974 (Reference 4). The
discharges and lOa-year water-surface elevations used in this Flood
Insurance Study were taken from the COE report. Elevations shown in
this study differ from those presented in the Flood Plain Information
Report due to the use of different cross section stationing.

A drainage study has been completed for the Tri-Area Drainageway at the
Town of Firestone which includes flood discharges and proposed
improvements (Reference 16). These discharges, developed by using the
Colorado Urban Hydragraph Procedure (CUHP), are approximately 25 percent
higher than those computed for this study. Because of the difficulty in
using the CUHP in undeveloped, agricultural watersheds, the discharges
determined in this report are considered appropriate. The discharges
reported here also include the effect of failure of the Frederick Levee,
which was not considered in the drainage study.

Gingery Associates, Inc., has
completing Flood Insurance Studies
Fort Lupton, and the Towns of

completed or is in the process of
for the Cities of Greeley, Evans, and
Frederick, Firestone, Dacono, Erie,

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