# Study on Temporal and Spatial Distribution of Landslides in the Upper Reaches of the Yellow River
## 3 Temporal and Spatial Distribution of Landslides in the Upper Reaches of the Yellow River
### Spatial Geometric Distribution Characteristics of Landslide
The Yellow River tributary is generally narrow, the free surface is limited, and the wide body landslide is developed. From the material composition type, it belongs to the semi-consolidated diagenetic landslide, and the plane shape is mainly presented as semi-elliptical, dustgun-shaped, saddle-shaped, semi-arc-shaped, etc. The sliding distance of this type of landslide is short, and the back wall is well-preserved and has a straight and steep shape. Therefore, these two types of landslides are obviously different from each other in terms of sliding body morphology and material composition. Among the 508 landslides in the study area, there are 303 landslides with a length greater than their width. There is a certain relationship between the length (L) and the width (W) of the landslide body. When the length and width of the landslide body are less than 1500 m, the ratio of width to length is close to 1, and this kind of landslide accounts for more than 1/5 in the study area. However, when it is greater than 1500 m, the length and width show a linear relationship, extending in the direction of polarization, but the overall increase in length is greater than the increase in width. The length-width ratio peaks at 2 and 3.2, reflecting that the length of some landslides is 2 times, 3 times, or even more than the width (Figure 6a). When it is greater than 1500 m, the length and width show a linear relationship, extending in the direction of polarization, but the overall increase in length is greater than the increase in width. As shown in the following figure, the correlation coefficients between length and width are 0.87 and 0.76, respectively (Figure 6b). \begin{table}
\begin{tabular}{c c c} \hline
**Length Range/m** & **Number** & **Percentage of Total/\%** \\ \hline \(\leq\)550 & 111 & 21.9 \\
551-970 & 165 & 32.5 \\
971-1400 & 113 & 22.2 \\
1401-2670 & 92 & 18.1 \\
2671-4800 & 22 & 4.3 \\ \(>\)4801 & 5 & 1.0 \\ \hline \end{tabular}
\end{table} 
Table 4: Statistical table of landslide length. \begin{table}
\begin{tabular}{c c c} \hline
**Width Range/m** & **Number** & **Percentage of Total/\%** \\ \hline \(\leq\)560 & 175 & 34.5 \\
561–1040 & 144 & 28.3 \\
1041–1510 & 89 & 17.5 \\
1501–2930 & 71 & 14.1 \\
2931–5300 & 23 & 4.5 \\ \(>\)5300 & 6 & 1.1 \\ \hline \end{tabular}
\end{table} 
Table 5: Statistics of landslide width. The minimum thickness of 116 field survey landslides in the study area is 15 m, the maximum is 135 m, and the average thickness is 39.6 m. According to the classification standard of the thickness of the landslide accumulation body [26], the author counted the thickness of 116 landslides in the field survey and found that the thickness of the landslide body was mainly concentrated in 30-50 m, which was a deep landslide, accounting for 67.2% of the total number of surveys. In addition, there are 25 ultra-deep landslides greater than 50 m, mainly giant landslides, accounting for 21.6% of the total number of investigations, as shown in Table 6.  
Among the 508 landslides, the smallest area is 0.01 km\({}^{2}\), the largest is 16.26 km\({}^{2}\), mainly distributed in the range of 0.01-4 km\({}^{2}\), of which 319 landslides with an area of 0.8-1.5 km\({}^{2}\), accounting for the vast majority, mainly distributed in the small slopes of the Qunke-Jianzha Basin and the Hualong Basin on the north bank of the Yellow River. Generally, the height difference and the free surface are not large, and the stratigraphic lithology is dominated by loess landslides. The number of landslides with an area of more than 4 km\({}^{2}\) is small, mainly distributed on both sides of the mainstream of the Yellow River and some large tributaries. For example, the Xiazangtan landslide on the south bank of the Yellow River in the Qunke-Jianzha Basin is stage I, and the sliding body area is 14.12 km\({}^{2}\). The total residual volume of 116 landslides is 98.35 \(\times\) 10\({}^{8}\) m\({}^{3}\), and the average volume is 0.85 \(\times\) 10\({}^{8}\) m\({}^{3}\).