## 4 Model Verifications
### Simulation of Current and Sediment Transport in Jiaojiang Estuary  
The Jiaojiang estuary, the third largest tidal estuary in Zhejiang Province, China, was chosen for model verification (Figure 5). It is a typical macro-tidal estuary with predominantly cohesive fine sediment. Samples from Jiaojiang estuary show that nearly 90% of the sediment is clay and fine silt with a diameter below 10 \(\upmu\)m (Figure 6). More detailed information about Jiaojiang estuary is available from previous work [41; 42]. The hydrology data from April to May 2009 were chosen for verification to match the topography data. The morphology data were obtained from measured data in 2009. A discharge per-cell boundary was applied at the upstream boundary, and a long-term tidal surface elevation signal was used downstream. Additionally, measured sediment concentration profile was applied at the upstream boundary, and downstream sediment flux was obtained from sediment sampling stations. Based on the grading curve shown in Figure 6, five different sediment classes were chosen as representative sediment classes of the non-uniform sediment: 0.0014 mm, 10%; 0.004 mm, 15.2%; 0.016 mm, 30.5%; 0.031 mm, 12.5%. The grid cell sizes in the computation are 20-200 m within the Jiaojiang estuary mouth and 200-3500 m in the outer sea (Figure 5). The total area of the computational domain is approximately 2500 km\({}^{2}\). The time step is 10 s. Based on the available observations, the open boundary upstream of Jiaojiang River is controlled by water discharge, and the outer sea boundaries are governed by tidal elevations in the hydrodynamic simulations. The average size distribution of sediment samples was set as the initial sediment gradation.  
Figure 4: Bed level change caused by different inflow discharges during the erosion test [29].  
The model was validated by tidal levels from 27 April to 3 May 2009, as well as the current (speed and direction) and suspended sediment concentrations (SSC) during spring tide. Figure 7 compares the computed and observed tidal levels at several stations. The computed results are in good agreement with the measured values. Figure 8 compares calculated to measured flow velocities and directions, showing that both the magnitude and the direction of the computed velocity match the field data at each station. Thus, the present model is well suited to simulate tidal currents.  
Figure 5: Simulation domain and grids.  
Figure 6: Average size distribution of the sediment samples from the Jiaojiang estuary.  
Figure 7: Comparison of the computed and observed tidal levels.  
The time series of computed and measured SSC is shown in Figure 9. In general, simulated SSC is in agreement with measured SSC. Figure 10a,b indicate the simulated SSC distribution at the flood and ebb during spring tide, respectively. The turbidity maximum zone of Jiaojiang estuary is reasonably duplicated by the model, as shown in Figure 10a,b. These results demonstrate that the present model, which uses [PERSON]'s theories for non-uniform sediment transport, has the capacity to simulate non-uniform sediment transport in estuaries.  
Figure 8: Comparison of the computed and observed tidal flow velocities.  
Figure 10: (a) SSC distribution at the flood tide; (b) SSC distribution at the ebb tide.  
Figure 9: Comparison of the computed and observed SSC.