Current field techniques are available to quantify critical shear stress and erosion rates of cohesive bed/bank materials. For coarse-grained alluvium, critical shear stress is presumed to be in conformity with Shields’ diagram, where the primary parameter is the grain size. Shields’ diagram and modified curves are known to work well with loose bedload material. The hypothesis to be tested in this study is that when a previously buried alluvial deposit is unburied and exposed to erosive forces, its critical shear stress will be higher than suggested by a standard Shields diagram. This is due to increased grain interlocking caused by the history of consolidation due to shallow overburden. We hypothesize that the friction angle is the significant parameter to quantify this effect, which can be measured in the field using penetration tests common to geotechnical analyses in coarse-grained alluvium. This research is funded by the USGS Illinois Water Science Center.