8251

• UCREFRP Catalog Number: 8251
• Author: Rakowski, C. L. and J. C. Schmidt.
• Title: The Geomorphic Basis of Colorado Squawfish Nursery Habitat in the Green River Near Ouray, Utah.
• USFW Year: 1996.
• USFW - Doc Type: #93-1070,
• Copyright Material: NO

Draft Fmal Completion Report [0 UDWR for Contract #93 -I 070, Amendment 3

34

RESULTS

The components of this research address different scales and multiple disciplines: and this discussion of results

progresses from the small scale to the large. and from geomorphology to flow and sediment transport modeling to habitat

availability and ecology.

Geomorphology

Much of this study focused on the bank-attached compound bar in the upstream part of the 1.5-Ian reach (Fig.

15), While other types of bars exist in this reach, bank-attached compound bars were the predominate bar form and

most consistent contributor to available nursery habitat. The bank-attached bar in the 1.5-Ian reach was a persistent

channel feature whose maximum elevation was up to 1.75 m above base-flow stage during the period of this smdy. The

point bar in the downstream part of the reach (Fig. 15) was a lower elevation deposit (<0.75 m above base flow) that

changed greatly in emergent area at base flow during this study. Cross sections were numbered from downstream to

upstream (Fig. 15).

Geomorphic Characteristics and Changes of the
Bank.attached Cum pound Bar in the Upstream
Part of the 1.5-km Reach

The bank-attached bar in the upstream end of the 1.5-Ian reach was composed of 3 distinct units (Fig. 16). The

highest elevations of the bar ( > 95.0 m) were stabilized by saltcedar and willow. The main bar platform (94,0 - 95.0 m

in 1993, 93.75 - 95.0 m in 1994) was composed of bare white sand deposited and/or reworked during high discharges.

The lower bar platform (93.5 - 94.0 m in 1993 and 93.5 - 93.75 m in 1994) was composed of wet, white or silty dark

sands and was inundated by discharges less than about 100 mJfs.

This bar was first surveyed in 1986, and the bar was completely unvegetated at that time (Andrews and Nelson,

1989). The bar also extended further downstream than in any subsequent survey. These conditions presumably were

the result of the high annual discharges that occurred in the study area between 1983 and 1986. Vegetation had

colonized the high elevation part of the bar by September 1990.

This bar includes several geomorphic features. A chute channel dissected the bar between cross-sections 7

and 8 (Fig. 16) in 1993 and 1994. Facing downstream, a secondary channel followed the bank on river right (RR).