HR: 1330h
AN: H42E-1125    [PDF]
TI: Regional, Basin, and Local Factors Influencing the use of Synoptic Survey Data to Assess Anthropogenic Changes in Streambed Stability and Fine Sediment
AU: * Faustini, J M
EM: faustini.john@epa.gov
AF: Department of Fisheries and Wildlife, Oregon State University, c/o U.S. Environmental Protection Agency, 200 SW 35th St., Corvallis, OR 97333 United States
AU: Kaufmann, P R
EM: kaufmann.phil@epa.gov
AF: U.S. Environmental Protection Agency, 200 SW 35th St., Corvallis, OR 97333 United States
AB: To evaluate anthropogenic changes in stream bed stability or texture from synoptic stream surveys, we calculated relative bed stability RBS* as the ratio of the geometric mean bed surface substrate diameter to the estimated bankfull critical diameter. RBS* decreased with increasing watershed and riparian disturbance in a previous survey of Oregon and Washington coastal streams, but showed a greater apparent response in streams draining basins underlain by weak sedimentary rock than in those underlain by more resistant volcanic rocks. Systematic natural variation in RBS* (e.g., downstream trends, local variation due to channel morphology, regional differences due to geology or climate) might affect its utility as a routine assessment tool by leading to differences in the relationship between RBS* and land disturbance. To explore these issues, we sampled streams over a wide range of disturbance intensity and geologic erodibility in the northern Oregon Coast Range, eastern Oregon, and mid-Atlantic USA. In each of 17 watersheds we sampled 3 closely-spaced main stem reaches (25-50 km$^{2}$ drainages in the Oregon Coast Range and mid-Atlantic USA, 250-400 km$^{2}$ in eastern Oregon) and 3 reaches each in 1 to 3 smaller tributaries to assess local variability and within-basin longitudinal trends in RBS* relative to variation between watersheds with different land use intensity. Preliminary results show significant regional differences in RBS*. The northern Oregon coastal streams exhibited a wider range of RBS* values than the other two regions, with higher average RBS* but also the lowest values. These coastal streams also showed the strongest (inverse) relationship between RBS* and anthropogenic disturbance. Contrary to expectations, RBS* generally increased with watershed area in this part of Coast Range, although the downstream pattern of RBS* values within individual watersheds was quite variable.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2003 Fall Meeting