FLOOD09431

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Hydrologic Summary FlS State of Colorado
• Date: 4/1/1981
• Prepared For: FEMA
• Prepared By: Camp Dresser & McKee
• Floodplain - Doc Type: Educational/Technical/Reference Information

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and for Northeast Canon Drainage. The hydrologic analysis contained in the
Army Corp of Engineers "Floodplain Information Report, Arkansas River Basin
in Florence, Colorado," 1978 (Reference 4), summari zes di scharge- frequency
data for the Arkansas River in Canon City. The hydrologic method consisted
of a statistical gage data analysis of the USGS gage station in Canon City.
COM supplemented this analysis with three additional years of gage data and
found that the resulting flows were within the 90-percent confidence limi '
of the CaE frequency-discharge curve (see Figure 2). For this reason, the
flow rates, as developed by the Corp of Engineers, were recommended for use
in the fl ood insurance study of Canon Ci ty (reference our 1 etter to FEt1A
dated March 16, 1981). These flows have been presented in Table 1.

Existing literature was also reviewed for Northeast Canon Drainage. A
lOa-year floodplain study was carried out by Great Divide Engineering for
the Colorado Water Conservation Board, which was completed in March 1981.
The study util i zed the Soil Conservation Servi ce "Procedures for
Determining Peak Flows in Colorado" (Reference 9). The report and
floodplain study has been reviewed and accepted by CWCB. COM reviewed the
calculations and methodology applied in the study and found no
discrepencies or errors in the application of the SCS method in this basin.
For this reason the peak discharge for the lOa-year frequency was
recommended for use in the Flood Insurance Study. COM computed flow rates
for the 10- and 50-year frequencies since the eWeB study did not develop
these flows. The ses method and basic drainage basin characteristics as

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