Abstract: Lingdingyang is affected by the superposition of multiple dynamic forces including tides, river runoff, and typhoons, resulting in a complex sediment transport process. However, research on the impact of seabed sediment erodibility (characterized by critical erosion stress) as a key factor on sediment transport remains insufficient. In this study, the Sanford (2008) sediment consolidation model was integrated into the ECOMSED 3D water-sediment model. By setting up a reference case (with actual critical erosion stress) and two experimental cases with enhanced erodibility (where the critical erosion stress is 1/2 and 1/8 of the reference value, respectively), the sediment transport processes under the influences of spring tides, neap tides, and Typhoon Hato were simulated, and the effect of erodibility on sediment movement in Lingdingyang was investigated. The results show that seabed erodibility has a significant impact on the spatial distribution of suspended sediment. A decrease in critical erosion stress increases the concentration of suspended sediment in high-turbidity areas, expands their scope, and presents a tendency to extend downstream, which is more pronounced under strong dynamic scenarios such as typhoons. The response of seabed erosion and deposition to erodibility is heterogeneous: in the neap tide period, the northern area changes from deposition to erosion; in the spring tide period, the erosion intensity increases; and during the typhoon period, intensive erosion occurs across the entire area. The sediment exchange between the estuary and the open sea is affected by critical erosion stress: when the critical erosion stress decreases to 1/8 of the reference value, the proportion of sediment transported to the open sea increases significantly, while the change in sediment output is slight when the critical erosion stress decreases to 1/2 of the reference value. This study clarifies the mechanism by which erodibility affects sediment transport in Lingdingyang, which can provide a basis for optimizing the bed sediment parameters of the Lingdingyang water-sediment model and also offer references for studies on similar estuaries with cohesive sediments.