CORRELATING EROSION THRESHOLD AND PHYSICOCHEMICAL PROPERTIES OF NATURAL COHESIVE SEDIMENTS

摘要

The erosion threshold of cohesive sediments is an important parameter, because in water systems fine-grained particles are the major transport agent of many contaminants. However, the erosion behaviour of cohesive sediments, is not yet well understood. To gain some insight into the processes governing the stabilisation of cohesive sediments, various sediment properties were analysed for their correlation with the erosion threshold of natural fine-grained bed sediments, which was determined as a function of sediment depth. Sediment consolidation, grain-size, and biological slimes (EPS) were found to be significant factors influencing erosion resistance. The combined effect of these mechanisms could either be considered with the consistency index as one overall parameter or by combining the water content, the percentage of grains smaller than 20 μm, and the content of colloidal carbohydrates in a multiple linear regression model. Hence, the results highlight that the erosion threshold of fine-grained cohesive sediments is not governed by one single mechanism, but rather by a combination of physical, chemical, and biological processes which are active at the same time. For a better understanding of the erosion behaviour of cohesive sediments it seems therefore advisable to conduct further experiments with both, well defined artificial and undisturbed natural sediments.