9575

• UCREFRP Catalog Number: 9575
• Author: LaGory, K. E. and R. A. V. Lonkhuyzen.
• Title: Potential Effects of Four Flaming Gorge Dam Hydropower Operational Scenarios on Riparian Vegetation of the Green River, Utah and Colorado.
• USFW Year: 1995.
• USFW - Doc Type: \
• Copyright Material: NO

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2 METHODS
2.1 RIPARIAN FIELD STUDIES
From June 17 to 24, 1992, the authors participated in a data-collecting trip by raft
on the Green River from Flaming Gorge Dam to Split Mountain campground, a distance of
about 80 mi. Traveling by raft enabled the collection of data along the river, much of which
is largely inaccessible by road. Data were collected from June 17 to 22, 1992, along
27 transects between the dam and Echo Park, the confluence between the Green River and
the Yampa River. During this period, releases from Flaming Gorge Dam were steady (i.e.,
no fluctuations) and at the minimum allowable release (about 800 cfs); flows from the Yampa
River contributed an additional 1,200 to 1,500 cfs below Echo Park. Data from an additional
11 transects were collected below the confluence with the Yampa River. Characteristics of
the transects - including location, length, and total elevation change - are presented in
Tables A.1 and A.2 of the appendix. Transect data are presented in Table A.3. The
relationships between distance from the river and elevation above the river along each
transect are presented in Figures A.1 through A.11. Photographs of the riparian zone in five
different reaches of the river are shown in Figure 2.
Transects were placed perpendicular to the river from the water to the upper outside
edge of the riparian zone, and data on species occurrence were collected at sampling points
located at 0.5-m (1.6-ft) intervals along the transects. Relative abundance of species was
determined from the transect data by calculating the percentage of sampling points at which
a species was recorded. (See Goldsmith and Harrison [1976] for a discussion of the use of
transects in determining species distributions across gradients.) Elevation was measured
with a hand level at points of discernible change in slope along the transect (e.g., a bench or
terrace), and the elevation of sampling points in between was calculated using slope and
distance values (see Table A.2). The outside edge of the riparian zone was readily
discernible; beyond this edge, plant cover was reduced, xerophytic plants (e.g., sagebrush and
cacti) were dominant, and mesophytic or hydrophytic species did not occur or were much
reduced. A steep slope or cliff sometimes defined the edge of the riparian zone. The wetland
indicator status of each species found in the riparian zone was determined from Reed (1988).
2.2 AERIAL VIDEOGRAPHY
Three-band multispectral aerial videography was collected under different flow
conditions at four selected segments of the Green River - Red Canyon, Little Hole, upper
Browns Park (Taylor Flat), and lower Browns Park (near Swinging Bridge) (Figure 3). The
videographic system used three video cameras mounted on a fixed wing aircraft to
simultaneously record ground reflectance in three different spectral bands (Neale 1992).
Separate video cameras recorded the green (0.55 pm), red (0.65 pm), and near-infrared
(0.85 pm) bands of the electromagnetic spectrum. These bands are similar to the Landsat
Multispectral Scanner green, red, and infrared bands that are used extensively for
determining vegetation classes. During each videotaping flight, system operator comments