## 3 Results  
### Validation of the River Engineering Model  
The repeatability of movable-bed sediment-laden river model tests is crucial. To ensure the repeatability and accuracy of the experiments, this study implemented a series of measures. The terrain was created using a longitudinal profile control template with intermittent sections to ensure that the initial riverbed morphology was consistent and accurate for each simulation. Initial riverbed topographic conditions were precisely controlled and recorded, and the sediment concentration was accurately controlled by using two pipes: one for drawing water from a sediment-laden mixing pool and the other for clear water. The inflow of water and sediment was regulated according to a generalized flood sequence table to ensure the accuracy of the sediment concentration at the upstream entrance.  
Throughout the experiment, all repeated tests utilized consistent high-precision calibrated measuring instruments, and the model was validated using the measured pre-flood and post-flood data from the river section in 2021.  
1. Validation of hydrodynamic drag similarity: The test used the measured pre-flood topography of the test river section in April 2021 as the initial topographic data, the water and sand process from April to October 2021 as the test water and sand process (Figure 3), and the measured water level and flow process of the water level and flow of the test section at the Lokou Hydrological Station as the model export control conditions for the verification test. By comparing the measured water level of the model with the measured water level of the prototype at the flow rate of 600 m\({}^{3}\)/s across five sections (Caoijaquan, Xidaokou, Lijiaan, Lujiazhuang, and Zhengjiadian; see Figure 5), the maximum error is 0.22 m, and the average error is 0.13 m. The results show that the model water level and the flow pattern are basically consistent with the prototype, reflecting that the model meets the drag similarity and flow regime similarity.  
\begin{table}
\begin{tabular}{c c} \hline
**Scale Ratio** & **Scale Value** \\ \hline Horizontal scale & 300 \\ Vertical scale & 60 \\ Velocity scale & 7.75 \\ Roughness scale & 0.88 \\ Discharge scale & 139,500 \\ Flow motion time scale & 38.71 \\ Settling velocity scale & 2.32 \\ Suspended sediment diameter scale & 1.24 \\ Sediment concentration scale & 2.47 \\ Riverbed deformation time scale & 43.55 \\ \hline \end{tabular}
\end{table}
Table 2: Summary of model design scales.  
Figure 5: Comparison of model test and prototype measured water level.  
2. Verification of riverbed deformation similarity: This is a comparison of a cross-section of 24 topographic data measurements (see Figure 6). Using the cross-section method to calculate the verification of the prototype and model siltation volume of the river section, we achieve a prototype cumulative scour volume of 39.52 \(\times\) 10\({}^{5}\) m\({}^{3}\), and a model cumulative scour volume of 32.14 \(\times\) 10\({}^{5}\) m\({}^{3}\). By calculating the ratio of the difference between the sedimentation and erosion volumes in the model test and those in the prototype river reach to the sedimentation and erosion volume in the prototype, the relative error was determined to be \(-\)18.68%. The error is in the permissible range, which indicates that the model siltation topography is basically consistent with the prototype [24], reflecting that the model meets the similarity of river bed deformation. The validation of the model shows that the results of the model can simulate the water and sand movement characteristics of the actual river channel.  
The results of the verification of flow resistance similarity and riverbed deformation similarity show that the water levels and riverbed scouring effects simulated by this model are within a reasonable error margin relative to the field measurements. This confirms that the model meets the requirements for simulation and prediction of this river's reach, with the experimental data being reliable to a certain extent.