HR: 0800h
AN: C41A-0052    [Abstracts]
TI: Riverine habitat and relative size of fluvial and glaciated valleys in central Idaho
AU: * Amerson, B E
EM: byron@stillwatersci.com
AF: Stillwater Watershed, Ecosystem, and Riverine Sciences, Inc., 2855 Telegraph Avenue Suite 400, Berkeley, CA 94705, United States
AU: Montgomery, D R
EM: dave@ess.washington.edu
AF: Department of Earth and Space Sciences, University of Washington, Johnson Hall 070 Box 351310 4000 15th Avenue NE, Seattle, WA 98195, United States
AB: Our recent investigation of glaciated and fluvial valleys in central Idaho compared differences in valley relief and width in otherwise similar geologic and geomorphic settings (Amerson et al. in press). We found that local valley relief and width in glaciated valleys is greater than in fluvial valleys. Local valley cross-sectional area in glaciated valleys increases with drainage area with, however, glacial valleys have greater cross-sectional area. Hillslope angle distribution differed between glaciated and fluvial valleys also; glaciated valleys have steeper hillslopes overall. The differences in valley form and in hillslope angle distribution in glaciated and fluvial valleys influences the channel type and therefore distribution of aquatic habitat in the river flowing through them. The distribution of anadromous salmonids (Oncorynchus spp.) is influenced by differences in stream gradient, pool density, and side-pool abundance. Glaciated and fluvial valleys have differences in the amount of low-gradient terrain (<5%), much of which is adjacent to streams (i.e. riparian zones). The broad flat valley bottoms of glaciated valleys have more low gradient terrain and therefore a greater total length of low-gradient reaches when contrasted with fluvial basins. Field observations in low order glaciated streams show that low-gradient areas consist of pool-riffle channels that are typically found in higher-order streams, which have floodplains that support a complex of side channels created by downed, large coniferous trees. Pool-riffle channels with abundant wood provide ideal habitat for anadromous fishes and the valley bottom morphology of glaciated valleys appears to help set the stage for productive fish habitat in upland regions of Idaho.
DE: 0720 Glaciers
DE: 0744 Rivers (0483, 1856)
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
SC: Cryosphere [C]
MN: 2007 Fall Meeting