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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City of La Junta, Colorado

The streams included in the flood insurance study for the community of La
Junta are Anderson and King arroyos and the Arkansas River (see Appendix B
for stream locations). During the search for existing literature, the Army
Corps of Engineers, "Special Flood Hazard Information, Arkansas River,
Anderson and King Arroyos, La Junta and Otero County, Colorado," 1977
(Reference 7), and the COE "La Junta Protection Project, La Junta,
Colorado, Design Memorandum No.1, Hydrology," 1978, were reviewed for use
in the flood insurance study. The hydrologic analyses of King and Anderson
arroyos in those two references used a synthetic unit hydrograph method to
develop peak discharges for the 10-, 50-, 100- and SOD-year recurrence
intervals. Basin data such as rainfall, rainfall losses, initial losses,
basin area, slope and development characteristics were reviewed and found
to be accurately estimated. It was therefore recommended that the flow
rates presented in Reference 7 be used in the flood insurance study for La
Junta. Due to the lack of adequate stream gage data for tributaries in the
plains region of the Arkansas River Basin, no attempt to develop a regional
relationship was made. The peak discharges for King and Anderson arroyos
have been presented in Table 1, (reference CDM's letter to FEMA and CWCB,
June 4, 1980, contained in Appendix A).

The hydrologic technique utilized by the Corp of Engineers in Reference 7
to determine the peak frequency-discharge data for the Arkansas River at La
Junta consisted of a stream gage analysis of the USGS gage station at La
Junta. The methods as outlined in Reference 15 were applied by the COE to
determine the peak discharges for this reach of the Arkansas River. CDr~

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