Application of parameters and paradigms of the erosion and deposition for cohesive sediment transport modelling in the Lingdingyang Estuary, China

Abstract Suspended sediment and the surficial sediment in most estuaries throughout the world consist of fine particles. Modelling cohesive sediment transport is an important way to explore the morphological evolution of estuaries where cohesive sediment is dominant. Various values for critical shear stress and deposition paradigms for cohesive sediment transport were evaluated here by analysis of field samples combined with numerical simulation in the Lingdingyang (LD) estuary in China. A UMCES-Gust Erosion Microcosm System (U-GEMS) experiment using field samples suggests that the experimental average value of critical shear stress for erosion (τce) is 0.26 N/m2. Two conflicting paradigms, i.e. mutually exclusive versus simultaneous erosion and deposition, are commonly used for cohesive sediment transport. Simulations of tidal currents and sediment transport during the wet season of 2007 and dry season of 2016 in the LD estuary were conducted under these two paradigms using the TELEMAC-2D hydrodynamic module and the sediment module SISYPHE in the TELEMAC model. Model verification under these two paradigms was carried out, and the τce parameters in the TELEMAC model were revised based on a U-GEMS experiment. The results showed the following. (1) The simulation results of the model in the LD estuary were satisfactory when an experimental average τce value of 0.26 N/m2 was used. (2) The simultaneous paradigm using a τce value of 0.26 N/m2 well explained the changes in the field-observed depth-averaged suspended sediment concentrations under all tidal regimes during the dry season, whereas the simultaneous paradigm using a τce of 0.15 N/m2 was more similar to observations in the LD estuary during the wet season.