7292

• UCREFRP Catalog Number: 7292
• Author: Anonymous.
• Title: Upper Colorado River Basin Study, Stream Channel Stability at Phabsim Sites.
• USFW Year: 1984.
• USFW - Doc Type: \
• Copyright Material: NO

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Clifton PHASIM sites following the very high spring runoff in
1984. Pending field visits to these sites and further analysis
of the current conditions, these sites are classified as
unstable. These sites are representative of current conditions
of the Colorado River in the vicinity of Grand Junction and use
of habitat represented by their condition is documented. Thus,
these sites are included in the analysis because of their
demonstrated utility despite apparent instability.

The Potash (Colorado River), Moab (Colorado River), Ouray Refuge
(Green River) and Mineral Bottom (Green River) PHABSIM sites
exhibit minor'changes in channel changes between photos. A trend
towar~s fewer channel bars and less sinous flow patterns (i.e.
more "canal-like" conditions) is apparent from comparison of
aerial photographs. Presumably, regulation of flow and sediment
is influencing the channel conditions at these sites. A
sensitivity analysis of these channels is recommended.
Simulation of habitat conditions based upon different channel
morphologies is possible using computer modeling. Habitat
conditions for channel conditions exhibited in historical
photographs can be compared to habitat conditions for current
channel morphology. With this approach, altered channel
morphology and it's effect upon habitat can be evaluated.

The remaining PHABSIM sites have been classified as stable. A
more intensive quantitative analysis of channel conditions and
stability is warranted for all sites. Our analysis is based upon
photointerpretation of channel conditions at two times.
Additional study of the intervening time period and present
conditions at all sites could provide explanation of the changes
observed and allow prediction of future conditions. Also, the
entire river system of the Upper Colorado River Basin should be
studied to determine how representative the PHABSIM sites are in
relation to channel conditions throughout the basin.