## 3 Results
### Heavy Rain Disaster Risk Assessment
#### 3.2.6 Risk Assessment and Validation  
Based on the SHAP interpretative analysis results, the impact values of various heavy rain disaster risk factors on regional disasters were obtained (as shown in Table 6). Using ArcGIS (version 10.8, ESRI) spatial analysis software, the risk factor data were standardized into raster layers with a 1 km resolution. According to the results in Table 6, these factor data layers were spatially overlaid with their corresponding risk impact values using Formula (6) to generate a heavy rain disaster risk level zoning map. ArcGIS is a GIS software developed by the Environmental Systems Research Institute (ESRI), a company in the United States. It is widely used for spatial data management and analysis, as well as map visualization. This study utilized the Spatial Analyst and Model Builder tools in ArcGIS to conduct zoning and spatial characteristic analysis of heavy rain disaster risks in this study. Based on the analysis results in Section 2.3.1, there was a considerable increase in the number of heavy rain days and total rainfall in the region from 2000 to 2017. Therefore, four years with notable changes in regional heavy rain disaster losses during this period were selected as typical years: 2003, 2005, 2012, and 2016. Heavy rain disaster risk assessments were conducted for each of these years, using the classification function of layer properties in ArcGIS to categorize the risk levels. The resulting maps of heavy rain disaster risk levels for each year are presented in Figure 8.  
The results indicate that the spatial distribution of various risk levels for heavy rain disasters in the study area exhibited significant dynamic changes during typical years. Examining the temporal and spatial trends of each risk level reveals the following:  
In Figure 8a, the overall trend of heavy rain disaster risk shows a decrease from southeast to northwest. The high-risk areas for heavy rain disasters are primarily concentrated in Tangshan City, Hebei Province, covering 10.92% of the total area. This is mainly related to the relatively high rainfall contribution rate occurring in this area within the year, with a value reaching 0.62, showing the characteristics of large total rainfall and high intensity. At the same time, the northern part of the city is located on the windward slope of the Yanshan Mountains. Floods caused by heavy rain quickly flow into the urban areas of the southern plains, and the design standard of the urban drainage network is far lower than the heavy rainfall intensity. Multiple factors lead to the high-level heavy rain disaster risk in this city. Medium-risk zones are concentrated in the southern, central, and northeastern regions, forming a band-like, transitional distribution surrounding the relatively high-risk zones. The low-risk areas are primarily located in the western part of the region. In Figure 8b, the high-risk zones are mainly distributed in the flood-prone areas in the southeast of Handan City, Xingtai City, Cangzhou City, and Hengshui City in Hebei Province. This is mainly due to the low density of regional drainage pipes, with an average of 6.45 km per square kilometer, resulting in limited drainage capacity, thus causing a higher risk of heavy rain disasters. The proportion of relatively high-risk zones increases compared to Figure 8a. Medium-risk zones are distributed in the central and northeastern parts of Hebei Province, while low-risk zones remained concentrated in the northwest. In Figure 8c, medium, relatively high, and high-risk areas are concentrated in the east-central region of the study area. Affected by continuous large-scale heavy rain events, the peak daily precipitation appeared at two stations in Tangshan City, Hebei Province, both reaching more than 170 mm. The high-risk areas are mainly concentrated in Tianjin, Tangshan, Qinhuangdao, and Langfang in Hebei Province.