The transport of cohesive sediment is known to be impacted by salinity and consolidation, which control the electro-chemical force and microscale structures of clay. However, such impacts remain poorly understood, due to a lack of direct visualization and characterization methods. Here, we combine a transparent clay, fluorescent dye, and laser-based technologies to directly visualize the transport of clay and its microstructure and identify the critical shear stress for clay erosion, Tau_crit. We show that as salinity increases, Tau_crit increases by over one order of magnitude under low salinity (<1.52 ppt) and then decreases under high salinity (>1.52 ppt). This non-monotonic dependence of Tau_crit on salinity can be attributed to a change in clay microstructures. In addition, we show an increase in Tau_crit after clay consolidation and attribute it to a change in clay microstructures. Our results demonstrate the important role of salinity, consolidation, clay microstructure, in controlling clay erosion.