# Estimation of River Velocity and Discharge Based on Video Images and Deep Learning
## 3 Results and Discussion
### Experiments in the Measurement of River Velocity and Discharge
#### 3.3.1 Experiment in an Artificially Repaired River  
In order to verify the actual measurement effect of the proposed method, the Agu hydrology station located in Yimen County, Yuxi City, Yunnan Province is selected as the experimental site. Agu station has been artificially repaired, the river section is regular, and the velocity is stable. According to the annual measurement records of the hydrology station, the velocity coefficient on the bank is 0.75, and the surface velocity coefficient is 0.89. The camera view for capturing video is shown in Figure 9; the points A, B, C, and D, marked with red boxes, represent the location of the selected ground calibration points, and AB is the cross-section line. The velocimetry points represented by yellow solid points \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Model** & **TOP1/\%** & **TOP5/\%** & **Param/M** & **FLOPs/G** \\ \hline ResNet34 & 64.14 & 90.74 & 21.37 & 3.68 \\ DenseNet & 62.35 & 90.00 & 7.04 & 2.90 \\ MobileNetV2 & 58.40 & 89.26 & 2.33 & 0.33 \\ EfficientNetV2 & 62.53 & 90.86 & 20.28 & 2.90 \\ GhostNetV1 & 58.21 & 87.35 & 4.01 & 0.15 \\ ShuffleNetV2 & 58.70 & 89.81 & 5.56 & 0.63 \\ Improved & 64.69 & 90.56 & 4.44 & 0.45 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of experimental results of different networks. are set at distances of 2 m, 4 m, 6 m, 8 m, 10 m, 12 m, 14 m, 16 m, 18 m, and 20 m from point A, respectively, and are sequentially numbered from No. 1 to No. 10. The yellow lines are velocimetry lines laid at each measuring point. A Hikvision DS-2 DC7423 camera is fixed at distances of 24.2 m, 2.7 m, 8.5 m, 29.3 m from points A, B, C, and D, respectively, to record 5s of river video images, and the frame rate is 60 fps. Table 6 presents the cross-section data and values measured by the LS25-1 current meter. The results and errors derived from various methods are shown in Table 7. The intuitive comparison results and errors of vertical mean velocity, total discharge, and mean velocity are depicted in Figure 10. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Points**} & **Starting** & \multirow{2}{*}{**Depth/(m)**} & **Vertical Mean** & **Partial Mean** & \multirow{2}{*}{**Partial Area/(m\({}^{2}\))**} & **Partial** \\  & **Distance/(m)** & & & **Velocity/(m/s)** & & **Velocity/(m/s)** & **Discharge/(m\({}^{3}\)/s)** \\ \hline \multicolumn{7}{c}{0 (shore)} \\  & 0-2 & & & 0.52 & 1.22 & 0.59 \\ No. 1 & 2 & 0.54 & 0.69 & & 0.83 & 1.01 & 0.84 \\ No. 2 & 4 & 0.48 & 0.97 & & 0.96 & 0.93 \\ No. 3 & 6 & 0.48 & 0.97 & & 0.97 & 0.99 & 0.96 \\ No. 4 & 8 & 0.51 & 0.97 & & 0.92 & 1.02 & 0.94 \\ No. 5 & 10 & 0.53 & 0.87 & & 0.75 & 1.18 & 0.89 \\ No. 6 & 12 & 0.60 & 0.63 & & 0.66 & 1.28 & 0.85 \\ No. 7 & 14 & 0.61 & 0.69 & & 0.64 & 1.16 & 0.74 \\ No. 8 & 16 & 0.53 & 0.58 & & 0.55 & 1.05 & 0.58 \\ No. 9 & 18 & 0.48 & 0.52 & & 0.46 & 1.01 & 0.47 \\ No. 10 & 20 & 0.52 & 0.40 & & 0.30 & 1.24 & 0.37 \\  & 20–23 & & & & & & \\  & 23 (shore) & & & & & & \\ \hline \multicolumn{7}{c}{Cross-section area/(m\({}^{2}\)): 12.12} \\ \multicolumn{7}{c}{Discharge/(m\({}^{3}\)/s): 8.19} \\ \multicolumn{7}{c}{Mean velocity/(m/s): 0.68} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Data of cross-section and the LS25-1 current meter in Agu. Figure 9: Ground calibration points and velocimetry lines in Agu. The total discharge and mean velocity measured by the proposed method are 8.37 m\({}^{3}\)/s and 0.69 m/s, respectively. The absolute errors are 0.18 m\({}^{3}\)/s for discharge and 0.01 m/s for mean velocity, with relative errors of 2.20% and 1.47%, respectively. Compared with the GTM, FFT, and FD-DIS-G methods, the accuracy of discharge is increased by 10.99%, 6.96%, and 14.53%, and the accuracy of mean velocity is increased by 11.77%, 7.35%, and 14.71%, respectively, which indicates that the results of the new method are closest to the true value of the current meter and exhibits a high degree of consistency.