Flume studies on the erosion of cohesive sediments

The erosion of kaolinite clay and bottom sediment from the Calcasieu River in Louisiana was studied in a straight recirculating flume under several bed shear stresses. The different types of experiments were: (1) detachment of kaolinite and river sediment from fine aggregate; (2) erosion of settled, consolidating samples; (3) erosion of kaolinite with adjustment of sediment pH; and (4) erosion of kaolinite with adsorbed natural aquatic organic matter.;The critical shear stress of the kaolinite was 0.76 N/m;A kaolinite sediment with pH ;The erosion rates of kaolinite for intermediate concentrations of adsorbed natural organic matter (NOM) (0.06 to 0.08 mg C/g clay) were approximately double those at the lowest and highest concentrations of adsorbed NOM (0.00 and 0.12 mg C/g clay). The erosion rates increased linearly as bed shear stress increased for all concentrations of adsorbed NOM. The increase in adsorbed NOM caused the kaolinite sediment to be more susceptible to erosion as evidenced by the decline in the values of critical shear stress. This is significant since sediments with higher organic concentrations may be more reactive with environmental contaminants and may also be more susceptible to erosion.