基于风险普查的地质灾害预警雨量阈值

Research on Rainfall Threshold of Geological Hazard Warning Based on Risk Census

摘要:

利用湖南省株洲市2011—2021年地质灾害灾情记录及区域自动站降雨资料，统计分析了株洲市地质灾害发生规律；以湖南省株洲市为例，分析了地质灾害与降雨量特征值的关系，探讨滑坡型地质灾害预警雨量阈值确定办法。结果表明，暴雨或以上强降雨是突发地质灾害的主要诱因，地质灾害不仅与当日降雨量有关，还与前期降雨量、降雨强度等密切相关；以有效降雨量、激活雨强作为致灾因子，利用箱形图分析法确定了不同预警分区内滑坡型地质灾害蓝色、黄色、橙色、红色预警雨量阈值；经典型过程反查和历史案例回算检验，以有效雨量为因子确定的地质灾害预警雨量阈值，可应用于地质灾害气象风险预警服务，激活雨强确定的地质灾害短临预警阈值指标偏低，空报率大，不宜单独使用。

Abstract:

The single-factor analysis and multi-factor comprehensive evaluation delineation method are used to evaluate the geo-disaster prone area, and the rainfall distribution characteristics and the frequency of geo-disasters are combined to determine the geo-disaster meteorological early warning area. Taking the towns and streets as early warning units, and the effective rainfall and activated rain intensity of geological disasters as the disaster-causing factors, the box plot analysis method is used to determine the rainfall threshold index value of all levels of landslide geological hazard. The method of typical heavy rainfall process combined with disaster reverse check and historical typical case back is used to test the rainfall threshold of geological disaster warning. From the statistical analysis of geological disaster census cases in Zhuzhou from 2011 to 2021, it is found that the geological disasters in Zhuzhou are mainly landslide disasters, followed by collapse, and small-scale geological disasters account for 98% of the total. The occurrence period of geological disasters in Zhuzhou is consistent with the rainy season, and landslide geological disasters are mainly distributed in Youxian County and Chaling County, and collapse disasters are mainly distributed in Lusong District and Hetang District. More than 80% of towns and streets in the city have experienced geological disasters. Geological disasters in Zhuzhou are closely related to rainfall, and heavy rain or more is the main factor for the formation of geological disasters in Zhuzhou. When the rain intensity is more than 20 mm/h, the risk of geological disasters in Zhuzhou is relatively high, and the risk of geological disasters induced by heavy rain intensity more than 50 mm/h is great. The critical value of effective rainfall for geological disasters in Liling is 61.9 mm, and the critical rainfall in other counties (cities, districts) is less than 50 mm, and the effective rainfall is more than 80 mm when more than 80% of geological disasters occur. The geological disaster meteorological early warning area of Zhuzhou can be divided into key early warning area A, sub-key early warning area B and general early warning area C. Each early warning area contains N early warning units of towns or streets. The effective rainfall and activated rain intensity are taken as the disaster factors. Using the box plot analysis method, it is clear that the disaster probability of 25% is the yellow warning rainfall threshold, the disaster probability of 50% is the orange warning rainfall threshold, and the disaster probability of 75% is the red warning rainfall threshold. The blue, yellow, orange and red warning rainfall thresholds of landslide-type geological disasters in different meteorological warning zones of Zhuzhou are determined. It is proved that the threshold index of early warning rainfall with effective rainfall as the disaster factor has a good application effect in practical early warning, while the threshold index of early warning rainfall with activated rainfall intensity as the disaster factor is lower and has a larger false alarm rate, so it should not be used alone in practical early warning.