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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at a given shear stress many different particle sizes may be at incipient motion.

in a gravel bed channel the range of shear stresses necessary for incipient motion
of a broad range of particle sizes is small, and the concept of equal mobility for
all grain sizes may be appropriate.

4.

Under certain flow conditions, large particles may be mobile under a smaller discharge,
and then become relatively immobile at a higher discharge. This apparent anomaly is
based on a well documented principle of fluid mechanics related to a reduction in drag
with a change in the boundary layer condition.

5.

Flushing of fme sediment from a gravel bed, without disruption of the armor layer, is
limited to about one median cobble particle diameter.

6.

The empirical Andrews relationship is recommended for quantifying incipient motion of
the bed layer itself in the Yampa River, providing conditions discussed in conclusion 3 do
not exist. These results should be compared to the analytical procedure by Wiberg and
Smith.

7.

The observations of Milhous and the empirical equations of Everts and those of Fisher,
Sills and Clark should be used to evaluate flushing flow incipient motion, recognizing that
more research will be required before this condition can be predicted with confidence.

8.

The occurrence of fine material at depth in the gravel bed is a natural condition in the
Yampa River.

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