9612

• UCREFRP Catalog Number: 9612
• Author: N.A.
• Title: Flaming Gorge Flow Recommendation Investigation FG-1 Technical Integration and Final Report - Hydrology and Physical Science Chapter - Draft.
• USFW Year: 1998.
• USFW - Doc Type: \
• Copyright Material: NO

• DRAFT February 25,1998
(RK 504), except for short, isolated stretches during a particularly severe winter.
Apparently the river gradient is too steep to allow progression past this point.
Analysis of the data collected during the 1997 field survey indicated that daily fluctuations
in releases from Flaming Gorge Dam have minimal effect on the hydraulic conditions in
the Green River downstream of RK 480 (Jensen Bridge). As a result, daily fluctuations
are unlikely to affect the formation of ice cover downstream of this point to any significant
degree. Upstream of this point the fluctuations have a more pronounced effect and can
affect the ice cover formation.
A numerical model of dynamic ice formation in the Green River was developed and
used to simulate the ice cover formation on the Green River for the winters 1989-90
through 1995-96. The ice model results are in general agreement with the historical ice
observations.
FLO Engineering, Inc. 1996. Green River Flooded Bottomlands Investigation, Ouray
Wildlife Refuge and Canyonlands National Park, Utah. FLO Engineering, Inc.,
Breckenridge, Colorado. 105p.
• Two study reaches were selected for the investigation of bottomlands flooding and
backwater inundation in the Green River. The first reach was located in the vicinity of
Ouray National Wildlife Refuge, near Vernal, Utah and the second reach was located in
Canyonlands National Park near Anderson Bottom. At Ouray, the frequently flooded
bottomlands were the subject of the investigation. In Canyonlands, the focus of the
investigation was the backwaters created by side canyon channels during high river flows.
Hydrographic data was collected at the two sites during the 1995 high flow season. An
analysis of U. S. Geological Survey stream gaging data for the period of record at the
Green River gages at Jensen and Green River, Utah, and simulation of flood levels using
the Corps of Engineers HEC-2 water surface profile model were also completed.
The results of the Ouray inundation analysis indicate that overbank flooding is initiated at
discharges ranging from 15,800 ft3/s to 22,700 ft3/s under existing conditions with levees.
If levees were removed, inundation may be initiated at most locations with discharges of
approximately 18,600 ft3/s. This discharge corresponds to a return period of 2.6 years
and an average annual duration of 4.4 days. Similarly, if 2 to 3 foot deep side channels
were excavated at appropriate locations to connect the bottomlands to the river, flooding
could be initiated at all Ouray bottomlands with a discharge of 13,000 ft3/s. The 13,000
ft3/s discharge has a return period of 1.5 years and an average annual duration of 11 days.
Through a combination of levee removal, side channel excavation and application
flooding, it would be practical to flood over 2,185 hectares at discharges on the order of
the 1.5 year return period. This would correspond to significant flooding every two out of
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