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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Flow Regulation and Channel Change
Loss of habitat resulting from a change in channel morphology is
another potentially important factor leading to the decline of the
endangered fishes. Since the channel morphology of ~lluvial rivers is
largely controlled by the flow regime (Schumm, 1969; Andrews, 1986), and
there are several dams and diversions in the upper Colorado River basin
that affect the flow regime, it is likely that changes in flows have resulted
in changes in channel morphology. Flow regulation encourages
vegetation encroachment and sediment deposition, and through time,
this process can lead to the development of new banks and the narrowing
of the channel (Williams and Wolman, 1984). Additional narrowing can
occur when low flows cause deposition of sediment in side channels,
vegetation becomes established, and the islands which once defined the
side channels attach to the floodplain (Graf, 1978).
There are numerous examples of how flow regulation has caused
channel change (Petts, 1979; Williams and Wolman, 1984). This has
occurred on the Green River in northeastern Utah which was dammed by
Flaming Gorge Dam in 1962. Before dam closure, mean daily flows
exceeded 140 cms (5,000 cis) more than 10% of the time, but now flows of
this magnitude do not occur (Andrews, 1986). The bankfull width of the
Green River has decreased by approximately 10% (Andrews, 1986). It is
likely that channel change from flow regulation has also occurred on the
upper Colorado River, but this study is the first to address this question.
In addition to affecting the channel morphology of the river,
regulating flows can adversely affect aquatic organisms. For example,
decreasing flow magnitudes can cause fine sediment to accumulate in
gravel spawning sites, which C<luses less flow past the eggs for oxygen

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