Long-Term Mobility and Storage of Sediments in Watersheds ofthe Upper Mississippi Valley

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The general objective of this research is to quantify the physical processes that influence the linkages, pathways, and time constants that separate erosion of sediment at its source and its ultimate removal from watersheds of the Upper Mississippi Valley. Responses of sediment mobility and storage to environmental changes in watersheds will be examined on three time scales, including: historical, Holocene (post- glacial), and late-Wisconsin (late-glacial). Results of the research contribute to improving the understanding of how environmental changes, operating at differing time and spatial scales, influence the type of quantity of sediment that is either stored or transported at various locations in watersheds of a humid climate region. Methodology includes: (1) field stratigraphic studies of sediment stored as colluvium, alluvial fan, terrace, and floodplain deposits, (2) laboratory sedimentological and geochemical analyses, and (3) statistical analyses that link archival data on climate, stream runoff, and land use to the field stratigraphic and laboratory results. The research should provide critical information that tests the hypothesis that erosion, storage, and delivery of sediment in watersheds is an episodic process that is dependent upon the occurrence of specific events which influence thresholds of sediment stability.