Influence of antecedent conditions on critical shear stress of bed sediments

Experiments were conducted in an annular flume using kaolinite clay and bed sediment collected within an industrial boat slip of Hamilton Harbour to assess their stability and transport characteristics. The critical shear stresses required to erode the sediment were measured under different conditions for bed formation. It was discovered that the way in which the bed deposited (i.e. deposited under quiescent conditions or under shear) had a strong influence on the stability of the bed. The critical shear stress for beds deposited under shear was up to eight times larger than that for beds deposited under quiescent conditions. The results suggest that modeling efforts which do not take into account the history of the bed formation may seriously underestimate the bed strength and as such, can result in erroneous predictions of sediment and contaminant source, fate and effect.