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LAND USE IMPACTS ON STREAM BED SUBSTRATE MODERATED BY GEOLOGY IN THE JOHN DAY BASIN, OREGON
Citation:
FAUSTINI, J. AND P. R. KAUFMANN. LAND USE IMPACTS ON STREAM BED SUBSTRATE MODERATED BY GEOLOGY IN THE JOHN DAY BASIN, OREGON. Presented at Association of American Geographers Annual Meeting, San Francisco, CA, April 17 - 21, 2007.
Description:
Human land uses and land cover modifications (e.g., logging, agriculture, roads) can alter runoff and increase sediment supply to streams, potentially degrading aquatic habitat for benthic organisms and fish. This study used synoptic stream habitat survey data from a regional assessment (N=58) to quantify stream channel substrate characteristics and relate these to human disturbance within the riparian zone and upstream catchment at local to whole-catchment scales inferred from field observations and remote sensing data. We assessed potential excess fine sediments using several indices of bed stability and excess fine sediments based on the difference between observed particle size or fine sediment abundance and empirically predicted values for least-disturbed sites. Bedrock lithology was an important natural control on the relationship between streambed substrate and human disturbance. Bed stability was significantly negatively associated with a field-based index of local human riparian disturbance in catchments underlain by resistant rock types, but only weakly negatively associated with riparian disturbance in catchments containing a significant proportion of erodible rock types. In contrast, bed stability in resistant basins was significantly positively associated with catchment-scale road density, but strongly negatively associated with road density in basins underlain by erodible bedrock. Our results suggest that roads are an important form of (or surrogate for) human disturbance in this landscape, and that geology may play an important role in determining the response of stream channel substrate to human landscape and riparian disturbance. Disclaimer: This is an abstract and does not necessarily reflect EPA policy.