9568

• UCREFRP Catalog Number: 9568
• Author: Resource Consultants Inc.
• Title: Sediment Transport Studies of the Little Snake, Yampa, and Green River Systems.
• USFW Year: 1991.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

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3.6 Bed Material Data in Yam.pa Canyon

Surface material gradation of the cobble bars in the spawning reach of Yampa Canyon was
evaluated based on grid-by-number techniques (see Section 33.2). The results of this analysis are shown in
FIg. 3.9. The particle size range of the cobble bar surfaces in the canyon was 30-150 mm. At river mile 16.5,
a documented spawning site, the d50 is about 38 mm at the sample location.

The gradations of the sand sized material in the pools above nn 16.5 and 18.5 are shown in Fig.
3.10. Note that the d50 of these samples (3-7 mm range) compares favorably with the sand size material in
transport in the Little Snake River (see Fig. 3.8).

3.7 Special GeolofPcal Investi~ations

Bed material samples for major ephemeral tributaries to Little Snake River were collected to
explore the possibility of using geologic source tracing for predicting sediment supply sources. Samples
were collected at the five Little Snake stream gaging/sediment sites as a Helley-Smith bedload sample. In
some cases at low flow, bed material grab samples were also collected at these locations. Samples were
also collected in the thalweg of major tributaries to the Little Snake close to the points of confluence.
Analysis of these samples contributed to the sediment source area investigation (Section 63).

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