FLOOD06493

• County: Phillips
• Community: Paoli
• Stream Name: North Fork Frenchman Creek
• Basin: South Platte
• Title: Floodplain/Flood Control Project Feasibility Study
• Date: 9/1/1991
• Prepared For: Phillips County
• Prepared By: Charles F. Leaf, PE
• Floodplain - Doc Type: Floodplain Report/Masterplan

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4

overflow channel (figure 1). The base survey line was identified

in the field so that it can be re-estab1ished at the time of con-

struction or if needed for other uses. This survey was a controlled

traverse survey with monumentation.

c) Survey of ten cross-sections of the existing channel and the

overflow channel. Cross sections were extended a minimum of 1 foot

above the elevation on either side of the July, 1988 flood plain.

d) Survey of channel and valley cross-sections for hydraulic routings.

These cross-sections were located between County Road 19 and

County Road 23.
Plate 1 (Appendix I) is an aerial photo map which shows the location

and extent of each cross section. Appendix II contains the plotted

cross-sections.

Hydro109Y Analysis

The stream hydrology developed by the Corps of Engineers and Colorado

Water Conservation Board for North Fork of Frenchman Creek at Paoli is:

Flood Frequency Event

10 - year
25 - year
50 - year
100 - year
500 - year
July 30, 1989

Peak Discharge

350 cfs
1,100 cfs
2,100 cfs
3,900 cfs
8,100 cfs
9,700 cfs

Hydraulic Analysis

The hydraulic analysis determined water surface elevations for the July

30, 1989 flood event. All hydraulic calculations were computed using the

HEC-2 computer model for the design discharges. Flood profiles were calculated

by the standard step method employing the Corps of En9ineers HEC-2 computer

program. The July 30, 1989 profile was established from known "high water