2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 9
Presentation Time: 10:25 AM

Holocene Sediment Budget for a 10^3 Km^2 Drainage Basin


TUNNICLIFFE, Jon, Department of Geography and Environmental Studies, Carleton University, B349 Loeb Building, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada and CHURCH, Michael, Department of Geography, The University of British Columbia, Vancouver, BC V6T 1Z2, Canada, mchurch@geog.ubc.ca

Chilliwack River drains 1200 km^2 in the Cascade Mountains on the Washington-British Columbia border. We have assembled a summary sediment budget for the basin by reconstructing the end-glacial (c. 13 000 calendric years BP) topography and determining the eroded sediment volume by DEM differencing. A lake in mid-basin preserves a record of headwater fine sediment yield, whilst alluvial fans throughout the basin, including a large end-point fan, preserve coarse sediments. Using a 1-D model of river and floodplain evolution, constrained by textural, lithological and geochemical tracers, and some absolute dates, we have computed a summary history of sediment yield for the basin that gives insight into the timing of sediment movement and the parameters of the fluvial sediment transport system. The mass balance framework and simplified morphodynamic formulation provide insight into the complex response of the fluvial system following deglaciation.