In-Situ Determination of the Critical Bed-Shear Stress for Erosion of Cohesive Sediments

A new in-situ erosion meter has been developed to measure the in-situ bedshear strength of cohesive beds. It is assumed that the current velocity, at initiation of motion of the toplayer of the bed, can be used to compute the critical bed-shear stress. This critical shear stress is the characteristic parameter which can define different types of sediment beds. The in-situ measurements show that the test results are determined by the prevailing hydrodynamic conditions in the field (wave activity) and recent depositions rather than by physical and biological parameters.