BOARD00607

• Board Meeting Date: 11/22/1999
• Description: Directors' Reports
• Board Meetings - Doc Type: Memo

planning group is Dec. 8 in Craig. The opinion would evaluate the Upper Colorado Endangered Fish
Recovery Program's ability to ensure fish recovery while water development continues in the basin. e

At the meeting the group will review a draft Yampa Management Plan that has been developed by
the USFWS. The plan will include a discussion of legal mandates, the new historic and new depletions
that will be covered by the plan (at least 120,000 AF of existign depletions, plus 50,000 AF to meet
expected ne demands by the 2045); non-native fish control issues; fish passage issues; specific recovery
actions designed to offset depletion impacts; possible sources of augmentation water to fish habitat needs;
and, monitoring to evaluate progress. They will also discuss the Flaming Gorge flow recommendations
and report and how it relates to the Yampa and how the Yampa and other tributary flows are addressed in
the report. The USFWS may also present information about how it proposes to address depletions on
the White River and other tributaries.

Lower Elk River Streambank Stabilization: We hired ICON Engineering, Inc. for professional
services related to the Elk River Streambank Stabilization Project and Watershed Study. Funding for this
study ($20,000) was approved in 1998. ICON Engineering began work in September 1999 and has
completed a substantial amount of the engineering analyses. A progress meeting was held on October 27
in Steamboat to present the draft findings of the engineering study. The key highlights are:
. Field surveyed cross-sections ofthe lower Elk River. The survey information provided basic data
so that a hydraulic model could be developed to demonstrate the charmel thalweg profile, stream
velocities, floodplain capacity, and water surface profiles.
· Watershed characteristics and drainage areas from the various tributaries in the basin. This work
will be expanded on in the final phase of the study.
. Flood hydrology analysis and peak discharges from the 1999 and 1997 flood events for ..
comparison purposes. Flood frequency data for the Elk River near Milner are: 100-year flow = ..
6,200 cfs; 50-year flow = 5,900 cfs; 10-year flow = 5,200 cfs. The June 3, 1997 peak flood flow
was 5,740 cfs (approximately a 25-year event). The 1999 peak flood flow was approximately
4,430 cfs (less than a 10-year flow).
· Stream geomorphology to help identify the problems and needs along the lower reach of the Elk
River.
· The large meander (bend) in the Elk River approximately 1,000 feet upstream of the highway 40
bridge is at risk for further erosion and migration. Complete failure of the embankment and levee
system along the outside of the bend would be catastrophic for homes, state highway 40 and the
bridge, the county road, and the railroad line.
. Maximum stream velocities for the 100-year flood along the outside of the large meander (bend)
are on the order of 12 feet/second. This high velocity presents challenges for stabilizing and
mitigating the streambank to prevent a major disaster.
. ICON presented various alternatives for protecting the streambank in the most critical areas in
lower 0.9-mile reach of the river. Drawings and figures were displayed for the audience to present
the conceptual design features. The most feasible solution is to protect the bank with riprap, in
addition to providing a rock sill (grade control structure) at the upstream end of the meander.
. Cost estimates for various stabilization alternatives were also presented. The range of costs for the
minimal approach up to the recommended alternative is $60,000 to $1,000,000, respectively.

The meeting audience generally feels comfortable with the engineering results and
recommendations, although the estimated cost for improvements is much higher than expected. The tit

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