SPATIAL AND ISOTOPIC ANALYSIS OF SOIL EROSION AND SEDIMENT FLUXES IN THREE RAPPAHANNOCK RIVER TRIBUTARIES, STAFFORD COUNTY, VIRGINIA
The RULSE/SDR estimates that 332, 130, and 212 tons/yr are currently being delivered to Claiborne Run, Little Falls Run and Horsepen Run respectively. These results directly correspond to the level of anthropogenic impact observed, where Claiborne Run, which has the most human development, has the highest soil loss and Horsepen which is mostly forested has the least. Preliminary isotopic fingerprinting results shows that stream bank erosion and re-suspension of internally stored sediments are the dominants sources of sediments in watersheds characterized by increased human development, i.e. Claiborne Run. Whereas the more pristine Horsepen Run has suspended sediments reflecting a variety of sources. The Pb-210 soil core inventories results shows that grassland areas have erosional rates ranging from 0.02 to 2.5 tons/hectare/ yr and farmland has depositional rates ranging from 0.32 to 0.36 tons/hectare/ yr. These results show that human development greatly increases erosional processes as well as suspended sediment loads currently being observed in the Rappahannock River and its tributaries.