# Risk Assessment of Landfalling Tropical Cyclones in China Based on Hazard Risk Theory
## 3 Results and Discussion
### Sensitivity Analysis and Assessment of Natural Carriers  
This study calculated the standard deviation of elevation within adjacent \(5\times 5\) grid cells using the spatial analysis tool Domain Analysis in ArcGIS as a quantitative indicator of terrain variation. Subsequently, the impact of elevation changes and vegetation coverage on the sensitivity of natural carriers was assessed using Equation (6), followed by visualization, as depicted in Figure 7.  
As the main carriers of natural hazards, China's vast land area and diverse natural environments result in varying degrees of susceptibility to tropical cyclones across different regions. The elevation and vegetation coverage in each province and city contribute to mitigating the impacts of tropical cyclones after landfall, thereby reducing hazard risks. Standard values calculated from elevation and vegetation coverage indicators were used to compute sensitivity scores according to the weights in Equation (9) for natural carriers. To facilitate statistical analysis, the scores were multiplied by 100 for presentation purposes, and sensitivity was classified using the natural breakpoints method in ArcGIS, as shown in Table 5. Subsequently, the sensitivity of natural carriers in various regions of China was visualized using graduated colors, as illustrated in Figure 8.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Level** & **Low** & **Relatively Low** & **Moderate** & **Relatively High** & **High** \\ \hline Scoring range (\(\times\)100) & N \(\leq\) 17.54 & 17.54 \(<\) N \(\leq\) 34.25 & 34.25 \(<\) N \(\leq\) 51.36 & 51.36 \(<\) N \(\leq\) 68.79 & 68.79 \(<\) N \\ \hline \hline \end{tabular}
\end{table}
Table 5: Natural carrier sensitivity scores in the affected areas of tropical cyclones.  
Figure 7: Impact of each index of natural carrier sensitivity. (**a**) Terrain Elevation (**b**) Vegetation Coverage.  
From the assessment results shown in Figure 8, it can be observed that central Liaoning, Tianjin, the eastern and central-eastern parts of Hebei, Shandong, the eastern parts of Henan, the central-northern parts of Anhui, Jiangsu, and Shanghai exhibited relatively high or higher sensitivity levels. Central Liaoning is situated in the Liaohe Plain, while the central-eastern parts of Hebei and Tianjin are located in the North China Plain. The highly sensitive areas in Henan are situated in the Yellow River Plain, while the northern parts of Anhui lie in the Huaihe River Plain. Shandong, Jiangsu, and Shanghai are predominantly plains, with relatively lower vegetation coverage compared to other regions of China, thus experiencing lesser mitigation effects against tropical cyclones and exhibiting higher sensitivity levels. Conversely, the northern parts of Hubei are separated from Henan by the Funiu Mountains and Qinling Mountains, Zhejiang features a complex terrain of mountains and hills, and the southern parts of Anhui are divided by the Dabie Mountains. The eastern parts of Liaoning are crossed by the Changbai Mountains. Although these areas still have relatively low vegetation coverage, their variable terrain weakens the progress of tropical cyclones after landfall, resulting in moderate sensitivity levels. In the southern part of Guangdong, despite its high vegetation coverage and rough surface, its location in the Pearl River Delta Plain leads to a moderate sensitivity level. Other regions, influenced by the combined effects of terrain elevation and vegetation coverage, exhibit higher resilience against tropical cyclones, hence demonstrating lower sensitivity levels. With the development of China's green economy in recent years, the vegetation coverage of various cities has been increasing annually; however, the latest available vegetation coverage data were obtained for 2019, which may have affected the results regarding the sensitivity of natural carriers.  
Figure 8: Division of natural carrier sensitivity level.