Event Title

Repeat photography of the Colorado River Corridor in Grand Canyon National Park

Presenter Information

Milada Majerova

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-21-2010 10:15 AM

End Date

4-21-2010 10:20 AM

Description

There is an abundant record of sand bar change along the Colorado River in Grand Canyon National Park that is documented by repeat ground-level oblique photographs. We assembled photographs for 29 sites between Lees Ferry (River Mile 0) and Bright Angel Creek (River Mile 87) that were taken over a 30-year period. Despite a >90% reduction in sand supply to this reach most sand bars have eroded to only a minor degree. The most significant change depicted in the photographs is a proliferation in riparian vegetation that has recovered from widespread scour caused by high flows in the mid-1980s. Increased bar size caused by recent controlled floods in 1996, 2004, and 2008 have caused short-term bar aggradation that does not typically persist for more than 1 year. We also compared recent photographs with those taken from the 1890 Robert Brewster Stanton collection. Changes in sand amounts were classified using three categories, each representing different flow elevation zone - 1) < 25,000 ft3/s, 2) 25,000-50,000 ft3/s, and 3) > 50,000 ft3/s. In addition, changes in vegetation were evaluated for the entire site/sand bar. The construction of Glen Canyon Dam in 1963 dramatically changed the hydrologic and geomorphic environment of the Colorado River corridor in the Grand Canyon (U.S. Department of Interior, 1995). Operation of the dam, driven by hydropower demand, resulted in major reductions in peak flows, elevated base flows, and daily fluctuations in stage up to 1.5 m. The supply of fine sediment was reduced approximately 99% immediately downstream from the dam in Marble Canyon and 81-85% further downstream at Bright Angel Creek.

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Apr 21st, 10:15 AM Apr 21st, 10:20 AM

Repeat photography of the Colorado River Corridor in Grand Canyon National Park

Eccles Conference Center

There is an abundant record of sand bar change along the Colorado River in Grand Canyon National Park that is documented by repeat ground-level oblique photographs. We assembled photographs for 29 sites between Lees Ferry (River Mile 0) and Bright Angel Creek (River Mile 87) that were taken over a 30-year period. Despite a >90% reduction in sand supply to this reach most sand bars have eroded to only a minor degree. The most significant change depicted in the photographs is a proliferation in riparian vegetation that has recovered from widespread scour caused by high flows in the mid-1980s. Increased bar size caused by recent controlled floods in 1996, 2004, and 2008 have caused short-term bar aggradation that does not typically persist for more than 1 year. We also compared recent photographs with those taken from the 1890 Robert Brewster Stanton collection. Changes in sand amounts were classified using three categories, each representing different flow elevation zone - 1) < 25,000 ft3/s, 2) 25,000-50,000 ft3/s, and 3) > 50,000 ft3/s. In addition, changes in vegetation were evaluated for the entire site/sand bar. The construction of Glen Canyon Dam in 1963 dramatically changed the hydrologic and geomorphic environment of the Colorado River corridor in the Grand Canyon (U.S. Department of Interior, 1995). Operation of the dam, driven by hydropower demand, resulted in major reductions in peak flows, elevated base flows, and daily fluctuations in stage up to 1.5 m. The supply of fine sediment was reduced approximately 99% immediately downstream from the dam in Marble Canyon and 81-85% further downstream at Bright Angel Creek.

https://digitalcommons.usu.edu/runoff/2010/Posters/7