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Last modified
7/14/2009 5:02:31 PM
Creation date
5/22/2009 6:54:01 PM
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UCREFRP
UCREFRP Catalog Number
7789
Author
FLO Engineering, I.
Title
Green River Jensen Spawning Bar & Escalante Wetlands Hydrologic Study.
USFW Year
1993.
USFW - Doc Type
\
Copyright Material
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A review of the cross section response to the 1993 high flow season reveals some <br />interesting channel morphology changes when comparing the April plots to the August plots. <br />Prominent amongst these changes is the redistribution of sand deposits and thalweg shifts. Of <br />the 23 cross sections, 10 cross sections experienced some net deposition, 6 showed scour, 5 <br />had no net change and 2 were not surveyed prior to the peak in April for comparison. <br />Throughout most of the study reach, there is a cobble bed underlying the sand bars and <br />sand substrate. In some areas of the channel, the sand bed is fairly deep and in other reaches <br />the cobble bed is exposed. Most of the cross sections around the spawning bar are cobble <br />substrate with small pockets or strings of sands. The 1993 peak flows were very high, <br />exceeding 20,000 cfs and redistribution of the sand in the channel was extensive. A brief <br />discussion of the channel response follows. These comments supplement those in Table 2. <br />• While cross section E-1 showed no significant change during the high flows, more <br />than 3 ft of sand was deposited in the mid-channel of E-2. This deposit was <br />removed during the recessional limb of the hydrograph. E-2 is located on the <br />downstream extent of a sharp right bend in the river. On the inside of the bend a <br />cobble bar has evolved. In 1993 sand deposition occurred over cobbles. <br />• Cross section E-3 was located at the upstream tip of the spawning bar. The plot of <br />this cross section in Exhibit A, sheet 1 illustrates that a large quantity of sand (4 ft <br />deep) was deposited at the start of the right channel. Except for the area near the <br />right bank, this deposit was removed during the recession limb of the hydrograph. <br />• Cross sections E-4 and E-5 experienced some sand deposition over the cobble bed <br />in both channels around the spawning bar during the peak flow. Nearly 4 ft of sand <br />was deposited in the right channel and only a portion of this deposition was removed <br />by mid-August. It is unclear if the sand will be removed by the 1994 spring runoff. <br />• Cross sections E-S.1 and E-5.2 were not surveyed in April. These two cross sections <br />are located just downstream of the spawning bar. E-5.1 experienced a large sand <br />deposit in mid-channel during the peak. Most of it was removed by August. <br />Conversely, E-5.2 stored sand during the period between the peak flow and the <br />August survey. This deposit may be the result of some of the sand being removed <br />from the right channel around the spawning bar (E-=1). <br />13 <br />
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