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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3

fea~tDi1ity study considered three alternatives for a flood control project.
Each alternative w.ou1d provide a h.igh 1eye1 of flood protection for the town.
By implementing the first and second alternatives presented in this report,
virtually all of the communi'ty would suffer only minimal damage from a flood
of the magnitude experienced on July 3D, 1989. Alternative 3 is a scaled-back
version of Alternative 2. Destgn flaws are based on a flood of lesser magnitude
than tha t experienced in 1989..

Existing'F1ood Patentia1

The Colorado Water Conservation Board summarized three flood parameters
ass:ociated with existtngf100d potential as follows:
1. Mai.n Channel Flooding - At County Road 19, the flooded areas were
contained in the natural floodplain.
2. Split Flow' for Flooded Areas - The U.S. Highway 6 and Burlington
Northern embankments acted as a diversion dike within the Narth
Fork Frenchman Creek f10adp1ain. During the July 1989 flood the
diversion of f10adwaters from the natural drainage
was substantial. At the U.S. Highway 6 bridge, it has been
estimated that seventy percent .of the floodwaters were diverted to
the east thrQugh the Tawn of Paoli. These floodwaters were diverted
to South Fork Frenchman Creek basin downstream .of Paoli. The path
of the diverted floodwaters is shown on figure 1,
3. Bridge Conveyance - The capacities .of the U.S. l:li.ghway 6 and
Burlington Northern Rai.1road bridges''iJre limited. These limitations
are contriouted to by a lack of channel capacity upstream of the
b,ridges; reduced bridge openings; and non-existent natural overbank
f100dp1atn areas.
The parameters above were quantified by field control surveys and a
hydraulic analysis as discussed below and in the Technical Appendix.

Field Control Surveys

The field control surveys included the following elements;
a) Acquisition of recent aerial phot09raphy and base map(s) from the
Colorado Water Conservation Board.
b) Establishment of a base survey line for the center line .of the existing