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 Final Completion Report to UDWR for Contract #93-1070, Amendment 3

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Other Surveys

Maps of flow patterns within the 1.5-lem study reach were made on 6 dates: May 22, June 11, June 23, and

August 13, 1993; and June 17 and July 16, 1994. Flow patterns of October 28, 1993, were mapped for RM 252.8 to

253.7 (below the 1.5-kIn study reach); flow patterns for RM 256 to RM 257 (upstream from the i.5-lem study reach)

were mapped on October 28, 1993 and July 16, 1994. Mylar or tracing paper overlays were used with the most recent

Reclamation video prints. The main thalweg, shallow and low or no velocity areas were mapped. Particular attention

was given to the location of shear zones that separate the main flow from areas of recirculating or stagnant flow.

Use of Detailed Topography to Develop a
Localized Habitat Availability Curve

It would be most desirable to develop a habitat availability relation using data from the entire 10-Ian reach. In

this study, it was necessary to use information from a smaller reach and relate that to the larger 10-Ian reach. Bank-

attached compound bars were the predominate bars within the to-Ian study reach, and consequently, a greater

understanding of the relationship of geomorphic features and habitat availability at these sites was crucial. A localized

version of a habitat availability curve was developed for the bank-attached compound bar within the 1.5-lem reach.

The digitized topographic maps of the detailed bar surveys were interpreted at each topographic level (0.25 m

increments) for areas of available nursery habitat. Using maps of flow patterns and experience gained mapping flow

patterns in this reach, the areas of probable nursery habitat were delineated for each topographic level of the surveyed

bar topography, and surface area of habitat was calculated as a function of stage and discharge.

Analysis of Video Prints

Schmidt (1996, unpublished manuscript) proposed using geomorphic mapping units to systematically measure

habitat complexity and mapped habitat attributes on a series of aerial photos taken in 1963. Differences in complexity

and habitat attributes were related to the characteristics of each river reach. These interpreted photos were digitized

into a GIS, and scaled using USGS quad maps.

Schmidt's (1996, unpublished manuscript) methodology was adapted to compare variation in channel edge

complexity as a function of time and changing discharge, and in order to relate the remotely-sensed measure of

complexity to actual habitat availability. Rather than comparing behavior of alluvial and canyon reaches of the Green