HR: 1340h
AN: H53B-1247    [Abstracts]
TI: A Comparison of Techniques for Mapping the Distribution of Sediment on the Bed of the Colorado River in Grand Canyon
AU: * Fuller, E
EM: aefuller@usgs.gov
AF: US Geological Survey Grand Canyon Monitoring and Research Center, 2255 N Gemini Dr., Flagstaff, AZ 86001
AU: Kaplinski, M
EM: matt.kaplinski@nau.edu
AF: Northern Arizona University, South San Francisco St., Flagstaff, AZ 86001
AU: Rubin, D M
EM: drubin@usgs.gov
AF: US Geological Survey Pacific Science Center, 400 Natural Bridges Drive, Santa Cruz, CA 35060
AB: The Grand Canyon Monitoring and Research Center is charged with establishing and implementing monitoring projects to provide scientific information to the Glen Canyon Dam Adaptive Management Program (GCDAMP) on the effects of operating Glen Canyon Dam on the downstream resources of the Colorado River ecosystem. One primary resource of concern to the GCDAMP is fine-grained sediment. Glen Canyon Dam traps approximately 94% of the pre-dam sand supply to the Colorado River in Grand Canyon, resulting in a decline in the size of eddy sand bars (25% decline in surface area over the past 15 years). Sand bars are an important resource because they provide habitat for endangered native fish, protect archeological sites, provide substrate for vegetation, are used as campsites and are a distinctive feature of the pre-dam environment. A combination of traditional survey techniques and multi-beam bathymetry has been used to determine the size and elevation of sandbars and to obtain topographic maps of the riverbed. These techniques have proven useful in evaluating the spatial changes and channel morphology along the Colorado River ecosystem. While previous studies have been very effective in measuring volumetric and spatial changes, a method is needed map the distribution of sediment along the submerged portion of the river channel. The distribution of fine-grained sediment is needed to evaluate the potential for deposition onto high elevation sand bars during proposed experimental high flows. This study used high-resolution multibeam bathymetry, acoustic backscatter and underwater video images collected on expeditions in 2002 and 2004 to evaluate the different methodologies. The purpose of this study was to evaluate possible technologies to be used in determining the distribution of sediment along the bed of the Colorado River in Grand Canyon. These technologies include: 1) visual interpretation of shaded relief images produced from multibeam bathymetry; 2) visual interpretation of acoustic backscatter images; 3) acoustic seabed classification using QTC Multiview. An evaluation of underwater video images was used to ground truth the various techniques. An evaluation of the results of each of the techniques, as well as a comparison of the efforts required will be presented.
DE: 3360 Remote sensing
DE: 3045 Seafloor morphology and bottom photography
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting