## 3 Results
### Percentage of Intercepted Sediment Mass  
In order to compare the role of each dam in the sediment interception of the cascade permeable dam, the percentage of intercepted sediment mass along the flows was obtained by dividing the sediment mass inside each dam or in front of the dam by the total intercepted sediment mass by the cascade permeable dam at the end of the experiment (see Figure 3). In this experiment, the percentage of intercepted sediment mass by 1-4# dam with large and small particle sizes ranges from 24% to 35%, 15% to 19%, 8% to 12%, and 4% to 7%, and 41% to 55%, 16% to 22%, 7% to 17%, and 4% to 8%, respectively. The dates show that 1# dam plays a major role in sediment interception, and the interception efficiency of the dams decreases along the flow direction.  
The permeable dam mainly realizes the sediment interception through physical filtration and dam material adsorption. For the small particle size, the pore is more likely to be blocked than the large particle size, and the sediment interception of the pore throat is more serious. Under different sediment concentrations, the overall percentage of intercepted sediment mass inside 2#, 3#, and 4# dam increases monotonically with the increases of the discharge. Under the same sediment concentrations, the percentage of intercepted sediment mass inside 1# dam and in front of 2# dam decreases monotonically with the  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Run** & **D 1 (mm)** & **Q 1 (L/H)** & **C 1 (g/L)** & **Run** & **D 1 (mm)** & **Q 1 (L/H)** & **C 1 (g/L)** \\ \hline
1 & & 300 & 1.0 & 10 & & 300 & 1.0 \\
2 & & 300 & 1.5 & 11 & & 300 & 1.5 \\
3 & & 300 & 2.0 & 12 & & 300 & 2.0 \\
4 & & 500 & 1.0 & 13 & & 500 & 1.0 \\
5 & 1–2 (Small particle size) & 500 & 1.5 & 14 & 3–5 (Large particle size) & 500 & 1.5 \\
6 & & 500 & 2.0 & 15 & & 500 & 2.0 \\
7 & & 700 & 1.0 & 16 & & 700 & 1.0 \\
8 & & 700 & 1.5 & 17 & & 700 & 1.5 \\
9 & & 700 & 2.0 & 18 & & 700 & 2.0 \\ \hline \hline \end{tabular}  
* The D, Q, and C refer to gravel particle size, discharge rate, and sediment concentration, respectively.  
\end{table}
Table 1: Experimental working conditions.  
increase of the discharge. At the discharge of 300 L/H, the flow velocity is relatively low, the sediment particles infiltrating into the dam interior will result in a transient equilibrium in the deposition of permeable dams. The percentage of intercepted sediment mass in 1#, 2#, and 4# dam decreases monotonically with increasing sediment concentration under the lower discharge. When the discharge increases to 700 L/H, the pore of the dam body is easily blocked as more sediment particles will be carried into the dam. The percentage of intercepted sediment mass inside 1# and in front of 2# dam increases monotonically with increasing sediment concentration, indicating that the sediment interception performance at this location is strongly influenced by the discharge. Under the highest discharge and large particle size, the percentage of intercepted sediment mass in 1# and 2# dam tends to increase first and then decrease with increasing sediment concentration, indicating that there is an upper limit to the sediment interception capacity of the dams for sediment-laden flow. When the sediment concentration is higher, the percentage of intercepted sediment mass inside 1# dam increases monotonically with increasing discharge, indicating that the first dam has a higher sediment interception capacity for a major flood.