## 4 Results
### Identification and Preliminary Validation of GALs in Lengqu River Section Based on RRIM
Considering that the number of GALs distributed in 30\({}^{\circ}\) sub-basins accounts for 85.19%, the threshold hillslope of 30\({}^{\circ}\) is selected at last in order to compare with the previous results that were obtained  
Figure 5: Display of Lengqu River section GALs identified by RRIM. by [PERSON] et al. at the same time. The results of excess topography extraction in the Lengqu River section are shown in Figure 7, and the thickness of excess topography is divided into 5 subintervals: {(0, 5], (5, 50], (50, 100], (100, 250], (250, 500]]] [27,29]. In Figure 7, it is shown that the excess topography is mainly distributed along the main Lengqu River and its tributaries, and the majority of the GALs are found to be developed on the excess topography on both banks of the river. \begin{table}
\begin{tabular}{l c} \hline \hline
**Location** & **Slope** \\ \hline Mode slope in Lengqu River section & 30\({}^{\circ}\) \\ Mean slope in Lengqu River section & 26\({}^{\circ}\) \\ Sub-basin b & 23\({}^{\circ}\) \\ Sub-basin c & 23\({}^{\circ}\) \\ Sub-basin d & 23\({}^{\circ}\) \\ Sub-basin e & 4\({}^{\circ}\) \\ Sub-basin f & 30\({}^{\circ}\) \\ Sub-basin g & 30\({}^{\circ}\) \\ Sub-basin h & 30\({}^{\circ}\) \\ Sub-basin i & 30\({}^{\circ}\) \\ Sub-basin j & 23\({}^{\circ}\) \\ Sub-basin k & 30\({}^{\circ}\) \\ Sub-basin l & 30\({}^{\circ}\) \\ Sub-basin m & 30\({}^{\circ}\) \\ Sub-basin n & 30\({}^{\circ}\) \\ Sub-basin o & 34\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Slope distribution of Lengqu River section. Figure 6: Slope distribution: (**a**) Slope distribution of the whole Lengqu River section; (**b–o**) Slope distribution of 14 sub-basins in Lengqu River Section. 2.1 Quantitative Analysis of the Relationship between the Location of GALs and Excess Topography in Lengqu River Section  
The surface morphology of GALs has changed over time, which means the deciphered GAL surfaces in Lengqu now are not in the same position as when the landslide first occurred. So, this research used a \"seed grid\" method to reprocess the existing 54 GAL surfaces. The \"seed grid\" [38] is to extract the effective areas around the existing landslide surfaces that can reflect the initial location of the landslides. Referring to the study of [PERSON] 2005 [39], the steps of \"seed grid\" extraction for landslide surfaces in this research are as follows: refer to the location of ridge lines in the RRIM, buffer landslide surface outward at an interval of 50 m (4 cells) based on the buffer surface not exceeding the ridge line and then re-edit the obtained buffer surfaces, only retaining the part of the landslide crown and both sides above the deposition areas. Based on the seed grid surface data of the 54 GALs, the relationship between GALs and excess topography is quantitatively analyzed, and the results are shown in Figure 8. The percentages of subintervals {(0, 5), (5, 50), (50, 100), (100, 250), (250, 500)] distributed on excess topography are 7.73%, 35.19%, 21.74%, 13.07% and 0.02%, respectively. A total of 77.75% of the GALs are distributed on the excess topography, which indicates that most of the GALs occur without changing the threshold hillslope at the location of occurrence. 2.2 Quantitative Analysis of the Relationship between Resurgent GALs and Excess Topography in Lengqu River Section  
Comparing the active slopes in the Pan-Sanjiang parallel flow area, six resurgent GAL surfaces were found to be located in the Lengqu River section, and since it is more difficult to obtain resurgent GAL data, this research first conducted a quantitative analysis based on the six monitored resurgent GAL surfaces with excess topography. Related results are shown in Figure 9a, and the percentages of resurgent GAL surfaces distributed in each subinterval ([0, 5], (5, 50), (50, 100), (100, 250), (250, 500)] of excess topography are 10.85%, 38.97%, 5.63%, 0.02% and 0.