8188

• UCREFRP Catalog Number: 8188
• Author: Muth, R. T., et al.
• Title: Flow and Temperature Recommendations for Endangered Fishes in the Green River Downstream of Flaming Forge Dam.
• USFW Year: 2000.
• USFW - Doc Type: \
• Copyright Material: NO

Final Report

3-8

September 2000

Creek), which contribute sediment during localized runoff events. The channel slope is about 0.002
in this part of Reach 1.

Downstream from Red Canyon, the Green River flows through the wide alluvial valley of
Browns Park for approximately 51 kID before entering Lodore Canyon. The channel in Browns Park
ranges from meandering to braided and is relatively flat, with a gradient of about 0.0008. The size
of bed material decreases through this segment, and in the lower 18 kID of Browns Park, the entire
channel has a sand bed. Bank erosion is a common source of sediment in this segment of the river.

In Lodore Canyon, the river channel is a series of linked straight reaches constrained by
steep rock walls. The bends that link the straight reaches are often coincident with geologic
structures (Grams and Schmidt 1999). The dominant channel features of this portion of Reach 1 are
debris fan-eddy complexes located at the mouths of tributary streams (see Section 3.6.1.2). The
channel gradient through the canyon is relatively steep (about 0.003).

Reach 2, between the Yampa River and White River confluences, is about 158 km in length
(Figure 2.1). Flow in this reach is recorded at the USGS gage near Jensen, Utah, about 46 km
downstream from the Yampa River confluence. This is a relatively long, meandering reach with
numerous subsegments having varying geomorphic characteristics. Reach 2 exhibits a more natural
flow and sediment regime than Reach 1 because of inputs from the relatively unregulated Yampa
River. Despite this fact, there has been a 26% decrease in the magnitude of the mean annual flood
at the Jensen gage since closure of Flaming Gorge Dam (Section 3.4). The Yampa River adds about
1.7 million metric tons of sediment to the Green River on a yearly basis. Mean annual discharge of
the Yampa River is about 56.6 m3/s.

Downstream from the Yampa River confluence at Echo Park, the Green River flows
through canyons and open alluvial valleys. Whirlpool Canyon extends for about 17 kIn below the
confluence and has a channel slope of about 0.002. Numerous rapids are located in this portion of
Reach 2, and debris fan-eddy complexes are common. Leaving Whirlpool Canyon, the river flows
through Island Park, Rainbow Park, and Little Rainbow Park for about 11 km. Multiple channels and
vegetated islands are common in these open areas, and the channel gradient is relatively low (about
0.0009). As it does in Browns Park, sand makes up most of the channel bed in these areas.

Downstream from Rainbow Park, the Green River enters ll-km-Iong Split Mountain
Canyon, where the river gradient is steeper (about 0.0038). From Split Mountain Canyon, the Green
River meanders through the broad valley of the Uinta basin for about 114 km to the confluences of
the Duchesne and White Rivers. Channel pattern is predominantly restricted meanders in the valley
(Section 3.6.1), and the gradient ranges from 0.0009 in the 15 kIn below Split Mountain to about
0.0003 for the rest of Reach 2. Bed materials range from cobbles to sand, and vegetated and
unvegetated islands are common. The Uinta basin portion of Reach 2 contains important nursery
habitats for the Colorado pikeminnow (in-channel backwaters) and razorback sucker (inundated
floodplains; Sections 4.2 and 4.3).