Comparison of Erodibility Parameters for Cohesive Streambank Soils between In Situ Jet Test Device and Laboratory Conduit Flume

Abstract

Several methods have been developed to estimate critical shear stress τc and the erodibility coefficient kd for cohesive stream banks/beds. This research compares estimates of these parameters between an in situ minijet device and a laboratory pressurized conduit flume. Estimates for τc between the two devices for the same soils were in general agreement compared with kd, especially for shear magnitudes greater than 5 Pa and consolidated soil with moisture contents greater than 20%. However, kd erodibility estimates between devices were significantly different. Operation of the minijet device applied a unique multiple-pressure setting (MPS) procedure that accounts for the change in soil properties with depth from the bank face. Both the minijet MPS approach and a conduit flume appeared to reduce the effect of surface subaerial process on erodibility parameter measurements, where τc and kd estimates were more similar compared with single-pressure test estimates using the Blaisdell, iterative solution, and scour depth solution computational procedures. Findings suggest τc and kd estimates are dependent on the device hydraulics, computational method, and soil properties.