HR: 1340h
AN: H53B-0466    [Abstracts]
TI: High Releases From Glen Canyon Dam Cause Short-term Eddy-bar Aggradation if Timed to Coincide With Significant Input of Sediment From Tributaries
AU: * Schmidt, J C
EM: jschmidt@cc.usu.edu
AF: Utah State University, Box 5280 Geography, Room 132, Logan, UT 84322-5210 United States
AU: Topping, D J
EM: dtopping@usgs.gov
AF: USGS - GCMRC, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Rubin, D M
EM: drubin@usgs.gov
AF: USGS - WR GD, Western Coastal & Marine Geology, Santa Cruz, CA 86001 United States
AU: Breedlove, M J
EM: mbreedlove@usgs.gov
AF: USGS - GCMRC, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Hazel, J E
EM: Joseph.Hazel@nau.edu
AF: Northern Arizona University, Dept. of Geology, Flagstaff, AZ 86001 United States
AU: Kaplinski, M A
EM: matt.kaplinski@nau.edu
AF: Northern Arizona University, Dept. of Geology, Flagstaff, AZ 86001 United States
AU: Wright, S A
EM: swright@usgs.gov
AF: USGS - GCMRC, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Fuller, A E
EM: efuller@usgs.gov
AF: USGS - GCMRC, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Melis, T S
EM: tmelis@usgs.gov
AF: USGS - GCMRC, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AB: Monitoring of fine-grained alluvial deposits in Marble Canyon of the Colorado River shows that controlled high dam releases from Glen Canyon Dam temporarily aggrade but do not completely reverse the long-term trend of bar degradation that has been measured during the past 45 years. Measurements made between 2000 and 2005 include short periods of high releases at the maximum capacity of the dam's powerplant in August 2000 and at the combined maximum capacity of the powerplant and by-pass tubes in November 2004. These high releases have temporarily aggraded eddy bars when the releases occurred at times immediately following large sediment delivery events from tributaries. Aggradation of eddy bars has also occurred during periods of fluctuating flows that generate hydroelectric power, if those flows occur during periods of major sediment inputs from tributaries. Smaller dam releases create eddy bars at relatively low elevations. Eddy-bars typically erode between floods, with initially high rates. Since August 2000, monitoring suggests that bar erosion has been greatest near Glen Canyon Dam and is less further downstream, suggesting that sand is longitudinally redistributed from upstream to downstream during periods when tributary inflow of sediment is low. The November 2004 high dam release also aggraded eddy-bars in Marble Canyon, but those bars were quickly eroded once daily peaks exceeded discharges of about 12,000 cubic feet per second for power generation.
DE: 1808 Dams
DE: 1815 Erosion
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: Fall Meeting 2005