1464 / 2024-09-27 15:05:07

Uncertainty and estimation of empirical coefficients of the PK formula for cohesive sediment transport modeling

cohesive sediment transport, numerical modeling, tidally-averaged equilibrium concentration

Session 24 - Estuaries and coastal environments stress - Observations and modelling

There is a puzzling fact for the Partheniades-Krone formula: when very contrasting values are adopted for the empirical parameters (e.g., the erosion coefficient and the critical shear stresses), satisfactory agreements for the suspended sediment concentration (SSC) can still be obtained. We derive a relation for the tidally-averaged equilibrium (TAE) condition by setting the integrated erosion flux throughout a tidal period equal to the integrated deposition flux throughout the same tidal period, leading to a new constraint on these parameters. A preliminary check using the measured data of the Yangtze Estuary shows that a larger critical shear stress for erosion would require a smaller critical shear stress for deposition. Contrasting sets of parameter values derived by this constraint are fed into a coupled hydro-sediment-morphodynamic model to simulate cohesive sediment transport in the Yangtze Estuary. The results confirm that very contrasting parameter values can indeed lead to satisfactory reproduction of the temporal variations of the SSC (e.g., those in July 2016, including both spring tide and neap tide). In addition, two simplified equations of the bed sediment mass conservation (no erosion version and the no deposition version) are derived as complements for obtaining a unique set of the three parameter values, provided that the simultaneous measured time series of SSC, bed shear stress and bed level can be collected at the same gauging station.