ABSTRACT:
Deforestation, agriculture, and urbanization affect soil erosion rates and while process-response models suggest a relationship between soil erosion and sediment yield, these models ignore the mitigating effect of intrabasinal storage and/or sediment conveyance rates. When the IVEX dam failed catastrophically in 1994, it provided an opportunity to study a dewatered reservoir containing new outcrops, and to collect vibracores. As a result of this, fourteen intervals were dated using historical flood records, the maximum depth of unsupported 210Pb, 137Cs peaks, paleosols, and pre reservoir sediments. The high sediment yield matched deforestation of the watershed during the 1840s-1850s. Subsequent rates declined 50% over the 1890s-1910s, despite peaks in land clearance for agriculture. From the 1910s-1960s, declines in farming corresponded to generally increased sediment yields. The watershed experienced 500% population growth during the post 1945 period, yet sediment yields were not correlated to population or new housing starts. Sediment yield appears strongly controlled by the occurrence of peak flows. This implies that changes in sediment conveyance rates can mask changes in land use practices.
Footnotes
James E. Evans is with the Department: of Geology at Bowling Green State University. Johan F. Gottgens is with the Department of Biology at the University of Toledo. Wilfrid M. Gill works with the Verde Environmental Company in Arizona and Scudder D. Mackey works with the Lake Erie Geology Group, Ohio Geological Survey.
- Copyright 2000 by the Soil and Water Conservation Society
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