Over the years, geological hazards such as collapses, landslides, hazardous rockfalls, and karst collapses have frequently occurred in Guangxi. These events are widely distributed, have prolonged impacts, affect large populations, and have caused heavy economic losses. Providing fundamental scientific knowledge for disaster prevention and mitigation in the region is of practical importance, as is conducting early prediction and risk assessment of geological hazards. The risk of geological hazards refers to the likelihood of a specific type and scale of hazard occurring within a defined area and time frame, influenced by certain triggering factors. Early prediction and risk assessment of geological hazards remain major challenges in disaster prevention and mitigation. Numerous factors influencing the risk assessment, and various evaluation methods have been employed.
This study adopted Xiangzhou county in Guangxi as a case and employed an information modeling method based on an investigation of the main geological conditions controlling potential hazards. Based on the overlay analysis function of ArcGIS on spatial data, eight evaluation indicators were selected according to the characteristics of geological hazard development and potential risks in the study area. These indicators include landform type, geological structure, engineering geological rock group and terrain slope, degree of karst development, slope structure, vegetation coverage, and human engineering activities. The engineering geological rock group and terrain slope were taken as the main controlling factors, while the remaining factors served as secondary factors for overlay zoning. After the natural breakpoint method in statistics was used to reclassify the susceptibility zones, an evaluation grid based on the value of information was generated to assess the susceptibility of geological hazards. The susceptibility of geological hazards in Xiangzhou county is divided into four levels:low, medium, high, and extremely high susceptibility. Areas with extremely high and high susceptibility are mainly located in river terraces, peak forests, and valleys where underground karst development is intense, as well as in rocky mountainous regions, and areas with significant human engineering activities. Areas with medium and low susceptibility are mainly found in hilly and low-mountain terrain. On the basis of susceptibility assessment and the meteorological characteristics of the study area, the maximum 24-hour rainfall data for various return periods were collected from rainfall stations in Xiangzhou county and its surrounding areas. The Kriging method in AcrGIS was used to generate contour maps for rainfall events with return periods in 10, 20, 50, and 100 years. The maps for assessment of geological hazard susceptibility and contour maps for different rainfall conditions were normalized, and spatial overlay analysis was conducted to produce maps for risk assessment of geological hazards corresponding to different rainfall return periods, quantified by the value of information. The risk probabilities was divided into four categories—extremely high risk, high risk, medium risk, and low risk—with the use of the natural breakpoint method, resulting in risk assessments of geological hazards for varying rainfall return periods.
The evaluation results indicate that as the return period of rainfall increases, the distribution area in which occur geological hazards with high and extremely high risks also expands. This result reflects that the impact of rainfall on geological hazards is significant. In Xiangzhou county, areas with extremely high geological hazard risk are mainly distributed in the central part near Sicun Town, characterized by river terrace landforms and rock formations with double-layer soil interbedded with sand gravel and clay. Additionally, extremely high-risk zones extend from the eastern Dale town to Baizhang town and to the western Maping town, where peak-forest valley landforms and hard limestone and dolomite rock formations characterized by karst intensely developed from the thick to blocky rocks are prevalent. The high-risk areas are mainly distributed in the hilly and river terrace landforms, including the northeast of Yunjiang Town, the area from Sicun Town to Dale and Baizhang Town, as well as the western part of Maping town. The remaining areas are mainly classified as medium- to low-risk zones, with hills and low mountains as the main geomorphic units. This study scientifically evaluates the geological hazard risks in Xiangzhou county, Guangxi, highlighting the key factors and adapting measures to local conditions. It categorizes different levels of geological hazard risks, and clarifies the zoning of these risks under different rainfall conditions. The findings provide a valuable reference for warning and forecasting geological hazards, improving the technical support system for hazard identification, zoning, and control in the study area. At the same time, the evaluation results can inform national spatial planning by guiding the population and economic activities to concentrate in low-risk areas in an orderly manner.
DownLoad: