ANALYSIS OF SOIL EROSION AND SEDIMENT TRANSPORT IN A SUB-WATERSHED OF THE RAPPAHANNOCK RIVER IN VIRGINIA

Erosion, a natural as well as anthropogenically induced process, if not closely monitored can be accelerated to the point where it becomes a major factor in large scale soil loss and environmental degradation.  With increased sediment fluxes, contaminants can be more quickly transported into rivers, bays or other basins. The rate of soil erosion and transport in a given watershed can be predicted by among other methods, isotopic and geospatial analysis. Deep Run basin (68.7 km²), a sub-watershed of the Rappahannock River in Stafford County, Virginia, is of high interest due to its location in the rapidly developing area of Northern Virginia. The basin is characterized by rapid land use changes due to increasing population pressures, is therefore a suitable site, in which evaluation of the potential impact of these changes in soil erosion and subsequently fluvial ecosystems would be appropriate.

The Revised Universal Soil Loss Equation (RUSLE) model in conjunction with sediment delivery ratios (SDRs) will be used to estimate watershed soil loss. The model analyses erosion in relation to geomorphic and land-use characteristics of the watershed.  Deposition within a watershed is a bi-product of soil erosion; therefore the rates of both processes should be relatively comparable. Pb-210 based sediment accumulation rates in a pond within the watershed shows results ranging from 0.068 g/cm²/yr to 0.078 g/cm²/yr with an average of 0.073 g/cm²/yr. The Pb-210 results will be compared and validated with sediment core Cs-137 analysis. The results of this study will provide the necessary data for formulation of better soil and water conservation practices.