## 3 Results and Analysis
### Analysis of Relief Degree of Land Surface and Surface Roughness  
According to Table 5, the study area has four classes: plains, plateaus, hills, and mountains. The landform type is mainly dominated by hills, which occupy 40.991% of the total area. Plateaus accounts for 33.441% of the total area. Plains accounted for 18.140% of the total area. Mountains accounted for 7.428% of the total area, which is the smallest. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Indicator** & **Total Area (km2)** & **Percentage (\%)** \\ \hline \multirow{4}{*}{Relief Degree} & Plains (\(<\)30 m) & 6.829 & 18.140 \\  & Plateaus (30–50 m) & 12.589 & 33.441 \\  & Hills (50–100 m) & 15.431 & 40.991 \\  & Mountains (100–200 m) & 2.796 & 7.428 \\ \hline \multirow{4}{*}{Surface Roughness} & 1 (Low roughness) & 20.418 & 59.278 \\  & 2 (Medium-low roughness) & 10.164 & 29.509 \\ \cline{1-1}  & 3 (Medium-high roughness) & 3.046 & 8.844 \\ \cline{1-1}  & 4 (High roughness) & 0.816 & 2.370 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Topographic feature parameters and their distribution. Figure 9: Slope direction, distribution, and area share of the study area. Analysis based on the relief degree of the land surface map (Figure 10a) reveals that the landform type on the outer side of the inner ring is mountains, with a substantial relief degree of land surface, steep ridges, and sharp changes in slope. When the terrain extends from the inner ring to the outer ring, the relief degree of the land surface decreases step by step. At the same time, the slope of the terrain also decreases gradually, which is positively correlated with the relief degree of the land surface. Its landform type shows a transition from mountains-hills-plateaus-plains (valleys). In the inner area of the Inner Ring Road, the landform type is mostly a striped plateau and hills with gentle surface undulation. Among them, the riverbanks on both sides of the main streams of the water system are strongly undulating. Like the relief degree of land surface (RDLS), surface roughness is divided into four classes (Table 5). However, their area share did not show the same trend. The surface roughness gradually increases from grade 1 to grade 4, but their area share shows a decreasing trend. Among them, the area of grade 1 is 20.418 km\({}^{2}\) with a percentage of 59.278%. Grade 2 follows it with 29.509%. Grade 3 is 8.84%. Grade 4 has the minor share, at 2.37%. Analysis of the surface roughness map (Figure 10b) revealed that surface roughness and relief degree of land surface (RDLS) have similar spatial distribution. The highest values of surface roughness were distributed in the outer part of the annular ridgeline, on both sides of the water system's mainstream channel, and in the eastern part of the freestanding hills. On the outer side of the inner ring line, the surface roughness gradually decreases from the inner ring line outward. In the inner area of the inner loop, the riverbanks on both sides of the water system's main streams have a high degree of roughness. The remaining areas have low surface roughness. In general, the study area exhibits a circular pit shape. As shown in Figure 10, within the inner ring there is a distinctly raised crest in the center of the terrain, with a high Relief Degree of Land Surface (RDLS) and roughness on both sides of the water system's mainstem channels in the southwest. In the ring belt area between the inner and outer rings, raised hills enclose a ring of ridges. Relief Degree of Land Surface (RDLS) values and surface roughness decrease gradually from the inner to the outer ring. The terrain within the inner ring is roughly divided into three major parts by the water system. In the northern and northwestern parts, the terraces and hills are arranged in a radial row with a roughly north-south orientation; in the central part, the terrain consists of terraces and  
Figure 10: Distribution of macrotopographic feature parameters: (**a**) relief degree of land surface, (**b**) surface roughness.