My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
9331
CWCB
>
UCREFRP
>
Copyright
>
9331
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
7/14/2009 5:01:47 PM
Creation date
5/20/2009 5:15:30 PM
Metadata
Fields
Template:
UCREFRP
UCREFRP Catalog Number
9331
Author
Allred, T. M. and J. C. Schmidt
Title
Channel narrowing by vertical accretion along the Green River near Green River, Utah
USFW Year
1999
USFW - Doc Type
Geological Society of American Bulletin
Copyright Material
YES
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
16
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
<br />.. <br /> <br />Figure 10. Changes in channel <br />characteristics over time. (A) Plot <br />of changes in measured channel <br />width extracted from U.S. Geo- <br />logical Survey (USGS) discharge <br />measurements made between <br />1930 and 1993; (8) plot of <br />changes in secondary channel <br />area detennined from aerial pho- <br />tographs taken at five different <br />times; (C) plot of mean channel <br />width determined from aerial <br />photographs. Note the similarity <br />in the overall trends for all three <br />plots. The dotted lines in 8 and C <br />represent possible naITOwing tra, <br />jectories suggested by the tempo- <br />rally rich USGS data. <br /> <br />-' <br /> <br />CHANNEL NARROWING BY VERTICAL ACCRETION, GREEN RIVER <br /> <br />110 <br />J: <br />I-~ <br />9 .5. 105 <br />3: <br /> <br />L5c- <br />a: ~ 0.4 <br /><~ <br /> <br />i= ~ 155 <br />oE <br />3: ~ 145 <br /> <br />the findings of Graf (1978) and Friedman et al. <br />(1996a, 1996b). However, our data also demon- <br />strate that riparian vegetation can only facilitate <br />vertical accretion at times when flood magni- <br />tudes are low enough so as not to remobilize <br />channel bars. <br /> <br />Processes of Channel Narrowing <br /> <br />Channel narrowing at the present cableway <br />and throughout the study reach occurred by <br />processes of bar stabilization and vertical accre- <br />tion. In some areas, narrowing occurred by filling <br />of secondary channels and conversion of a multi- <br />threaded channel into one with a single thread. <br />Our comparison of historical aerial photographs <br />shows that inset alluvial deposits have formed in <br />both straight and curving reaches, and can form <br /> <br />120 <br /> <br /> <br />PRE-DAM POST-DAM <br /> <br />115 <br /> <br />A MEASURED CHANNEL WIDTH - FROM USGS DISCHARGE <br /> <br /> <br />~ ~".. ."". ~ <br /> <br /> <br />. <br /> <br />. <br /> <br />100 <br /> <br />95 <br />0.6 <br /> <br /> <br />B SECONDARY CHANNEL AREA, IN SQUARE KILOMETERS - ROM AERIAL PHOTOS <br /> <br /> <br />0.5 <br /> <br />0.3 <br /> <br />0.2 <br />175 <br /> <br />165 <br /> <br />C MEAN CHANNEL WIDTH. FROM AERIAL PHOTOS <br /> <br />. <br /> <br /> <br />1960 <br />YEAR <br /> <br />1970 <br /> <br />1980 <br /> <br />1990 <br /> <br />2000 <br /> <br />135 <br /> <br />125 <br />1920 <br /> <br />1930 <br /> <br />1940 <br /> <br />1950 <br /> <br />Woodyer et al.(1979). Mayers and Schmidt <br />(Utah State University, unpublished data) found <br />similar evidence along the Green River in the <br />Uinta Basin, located about 320 kIn upstream <br />from the town of Green River. <br />Like other rivers with high suspended sedi- <br />ment loads, the vertically-constructed alluvial <br />benches of the Green River increase in elevation <br />with time relative to the channel bed. We found <br />no evidence in the study area for the type of cata- <br />strophic floodplain stripping that Nanson (1986) <br />described in Australian rivers. We also did not <br />find evidence for the rewidening of the Green <br />River channel in the study area by the large <br />floods of the 1980s reported by Lyons et aI. <br />(1992), and the rewidening that they measured <br />was probably less than the error of their analyti- <br />cal technique. In fact, we found no evidence of <br /> <br />TABLE 3. HYDRAULIC GEOMETRY OFTHE GREEN RIVER AT THE PRESENT GAGING STATION <br />NEAR GREEN RIVER, UTAH <br /> <br />Time period Width equation R2 Mean depth equation R2 Mean velocity equation R2 <br /> <br />1930-1938 71.2000.067 0.65 0.2400.390 0.94 0.0600.543 0.97 <br />1939-1957 76.7400.057 0.61 0.2200.408 0.96 0.06 0 0.536 0.97 <br />1963-1993 73.19 0 0.054 0.56 0.30 0 0.368 0.93 0.05 0 0.578 0.95 <br /> <br />Note: Q-discharge in m3/sec; R-correlation coefficient. <br /> <br />on the inside or outside of bends. We mapped the <br />conversion of entire channel bars into floodplain <br />areas, presumably by the same vertical accretion <br />processes we measured at the present cableway. <br />Although we observed horizontal bedding that <br />characterizes vertical accretion throughout the <br />study area, we do not know that all lower eleva- <br />tion surfaces formed at one time or that interme- <br />diate benches formed at another. For example, at <br />the present cableway, the entire deposit formed in <br />the second phase of narrowing, but the surface <br />correlates with intermediate elevation surfaces <br />elsewhere. <br />Thus, the Green River is probably constructing <br />two distinct topographic surfaces in the present <br />hydrologic regime, similar to what Pizzuto <br />(1994) found to occur on the Powder River. Sim- <br />ilar processes have also been described by <br /> <br />Geological Society of America Bulletin, December 1999 1767 <br />
The URL can be used to link to this page
Your browser does not support the video tag.