As water quality standards become more stringent, a knowledge of primary sediment source areas in watersheds becomes increasingly important from the standpoint of compliance through the design of efficient management practices that will reduce sediment and chemical loadings of receiving waters to acceptable levels. The objective of this research was to use a soil geomorphology approach to sediment sourcing to better define the effects of soil variability on erodibility and sediment transport at the watershed scale. Each major soil mapping unit in six subwatersheds (SWs) was sampled along transects positioned to include the normal soil geomorphological features associated with a given mapping unit. Soil samples collected from the surface 5.0 cm were characterized for basic physical and chemical properties, radionuclides, and stable C isotopes. These data were used as fingerprints for sediment source areas in the watershed. Suspended sediment samples collected from supercritical flumes at the mouth of each SW were analyzed identically. An aggregation index (AI), calculated for the soils in each SW as function of water dispersible clay/total clay), and used as an indicator of soil erodibility. The physical, chemical, and isotopic signatures of the suspended sediment collected at the six flumes were used in a multivariate mixing model to identify the primary contributing source. The results suggested that the SWs with the lowest soil AI were contributing the greatest amounts of sediment, which was confirmed by the stable C isotope data.