HR: 09:30h
AN: H31H-06    [Abstracts]
TI: Sprague River geomorphology studies, Klamath Basin, Oregon
AU: * McDowell, P F
EM: pmcd@uoregon.edu
AF: Dept. Geography, 1251 University of Oregon, Eugene, OR 97403 United States
AU: O'Connor, J E
EM: oconnor@usgs.gov
AF: U.S. Geological Survey, 10615 SE Cherry Blossom Dr., Portland, OR 97216 United States
AU: Lind, P
EM: plind@darkwing.uoregon.edu
AF: Dept. Geography, 1251 University of Oregon, Eugene, OR 97403 United States
AB: The Sprague River drains 4050 square kilometers with a mean annual discharge of 16.3 m³/s before emptying into the Williamson River and then upper Klamath Lake in southcentral Oregon. The alternating wide alluvial segments and narrow canyon reaches of this 135-km-long westward flowing river provide for a variety of valued ecologic conditions and human uses along the river corridor, notably fisheries (including two endangered species of suckers, and formerly salmon), timber harvest, agriculture, and livestock grazing. The complex history of land ownership and landuse, water control and diversion structures, and fishery alterations, provides several targets for attributing historic changes to channel and floodplain conditions. Recently, evolving societal values (as well as much outside money) are inspiring efforts by many entities to 'restore' the Sprague River watershed. In cooperation with the U.S. Fish and Wildlife Service, the Klamath Tribes, and many local landowners, we are launching an analysis of Sprague River channel and floodplain processes. The overall objective is to guide restoration activities by providing sound understanding of local geomorphic processes and conditions. To do this we are identifying key floodplain and channel processes, and investigating how they have been affected by historic floodplain activites and changes to the watershed. This is being accomplished by analysis of historic aerial photographs and maps, stratigraphic analysis of floodplain soils and geologic units, mapping of riparian vegetation conditions and changes, and quantitative analysis of high resolution LiDAR topography acquired for the entire river course in December 2004. Preliminary results indicate (1) much of the coarser (and more erodible) floodplain soils are largely composed of pumice deposited in the basin by the 7700 year BP eruption of Mount Mazama; and (2) the LiDAR digital elevation models provide a ready means of subdividing the river into segments with quantifiably different characteristics of channel width, sinuosity, slope, and incision (relative to adjacent floodplain elevations).
DE: 1825 Geomorphology: fluvial (1625)
SC: Hydrology [H]
MN: Fall Meeting 2005