HR: 17:30h
AN: H32I-07    [PDF]
TI: Watershed and mainstem river linkage on the Green River, Desolation and Gray Canyons, East-Central Utah
AU: * Elliott, C M
EM: celliott@usgs.gov
AF: US Geological Survey, Columbia Environmental Research Center 4200 New Haven Rd, Columbia, MO 65203 United States
AU: Schmidt, J C
EM: jschmidt@cc.usu.edu
AF: Utah State University, Department of Aquatic, Watershed, and Earth Resources, Logan, UT 84322 United States
AB: Tributary watershed characteristics strongly influence mainstem river form in the relatively wild tributaries of the Green River where it flows through Desolation and Gray Canyons in east-central Utah. In the135-km study reach, 164 tributary drainage basins and their characteristics as well as various attributes and field measurements of the mainstem river valley and channel were analyzed in a GIS in order to determine the effects of watershed processes on mainstem channel form. Bedrock geology controls valley width at tributary junctions, thereby controlling the accommodation space available for the formation of alluvial fans found at tributary junctions. These fans form from debris and stream flows that occur in tributary watersheds. Fans serve as the link between tributary watershed processes and mainstem channel form. Fan-river linkage is defined by connectivity between tributary processes and the mainstem river through an incised channel and the presence of reworked gravel bars associated with fans. A wide variety of types of fans occur at tributary junctions exhibiting varying degrees of linkage with the Green River. Many tributaries do not affect mainstem processes at all, and exhibit little linkage with the river. Tributaries that are linked to river processes often have incised channels in their alluvial fans. These channels serve as a conduit for coarse material to reach the mainstem and create riffles and rapids. The degree of linkage with the mainstem river is most likely related to the types and frequencies of watershed processes occurring in tributary basins rather than drainage basin size. Gravel bars also frequently occur in reaches with active debris fans, and the presence or absence of debris flow processes in a watershed directly influences the overall gravel bar distribution and mainstem channel slope on this reach of the Green River.
DE: 1724 Ocean sciences
SC: Hydrology [H]
MN: 2003 Fall Meeting