8221

• UCREFRP Catalog Number: 8221
• Author: Van Steeter, M. M.
• Title: Historic and Current Processes Affecting Channel Change and Endangered fish Habitats of the Colorado River Near Grand Junction, Colorado.
• USFW Year: 1996.
• USFW - Doc Type: Doctor of Philosophy.
• Copyright Material: NO

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what flows might form multi-thread channels through re-arranging bars
and eroding banks. Parker (1978) suggested that for gravel bed rivers with
non-cohesive banks, a shear stress 1.2 times the critical shear stress (tc) of
the bed material was needed to erode river banks. At ~his stress, the bed
material at the toe of the banks would become mobile, and bank erosion
would occur. The banks of the upper Colorado River are slightly cohesive
due to riparian vegetation, therefore complicating the situation. Andrews
(1984) determined that on gravel bed rivers in Colorado with thick
vegetation, stresses in excess of 2 times the critical shear stress were
necessary for bank erosion. Therefore, a discharge which yields a critical
shear stress equal to two times that for entrainment of the bed material
may be appropriate for the creation of habitat. Flows of this magnitude
can also disrupt the riparian plant community and select against
nonnative fishes which cannot survive high flow events.
In order to recover the Colorado squawfish, several questions must
still be answered. First, how have the habitats of these fishes changed?
Have channels become less braided, therefore causing a decrease in
habitat? Secondly, has there been a substantial change in the flow
characteristics of the upper Colorado River, and are these changes large
enough to affect the fishes and their habitats? Thirdly, if braided channels
benefit the Colorado squawfish, what flows are required to maintain and
create areas with multiple channels?

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OBJECTIVES
There are five major objectives of this project: 1) to t]uantifiJ
historic changes in channel morphology and relate these changes to fish
habitat; 2) to investigate these changes in relation to water development,