渝东北地区强降雨诱发地质灾害险情分析

渝东北一直以来都是地质灾害高发地区,地质环境条件脆弱,极端降雨事件频发,是区域地质灾害预警高度关注地区。以2014年8月底至9月初持续强降雨诱发地质灾害过程为例,运用统计方法,从空间和时间角度,分析地质灾害的空间分布、时间分布与降雨的相关关系,得到该区域降雨诱发地质灾害的规律特点及临界阈值。结果表明:①奉节、云阳、巫山属于地质灾害高易发区,巫溪、开县属于地质灾害中等易发区,其他地区属于低易发区;②渝东北地区的降雨模式常见为持续强降雨型(奉节)和暴雨型(云阳、巫山、巫溪及开县);③渝东北地区各区县临界雨强不同,奉节临界雨强为90 mm/d,险情特点有明显滞后性;云阳临界雨强为85 mm/d,巫山临界雨强为80 mm/d,巫溪、开县临界雨强推荐值为(100±5)mm/d;在持续强降雨作用且不小于30 mm/h的雨强下,险情伴随发生概率极高。渝东北地区强降雨诱发地质灾害险情分析成果,可为系统全面提出一套预警阈值、指导减灾防灾工作提供技术支撑。

Situation of Geologic Hazards Induced by Heavy Rainfall in Northeast Chongqing

The northeast of Chongqing City has always been a high incidence area of geologic hazard due to fragile geological environiment and frequent extreme rainfalls.It is also a highly concerned area of early warning on the regional geologic hazard.With the geologic hazard induced by continuous heavy rainfall from the end of August to early September in 2014 as a background,the relationship between spatio-temporal distribution of geologic hazards and rainfall are analyzed by using statistical methods from the point of view of space and time.The characteristics of geologic hazards induced by rainfall and the threshold of rainfall in this region are obtained.Results show that 1) Fengjie,Yunyang,and Wushan are highly prone to geologic hazards;while Wuxi and Kaixian are moderately prone to geologic hazards,and other areas belong to low prone areas;2) rainfall pattern in northeast Chongqing is commonly divided into continuous heavy rainfall (Fengjie) and storm (Yunyang,Wushan,Wuxi and Kaixian);3)critical rainfall intensities of counties in northeast Chongqing are different.The critical rainfall intensity of Fengjie is 90 ram/d,and hazard characteristic obviously lags behind,while the critical rainfall intensity of Yunyang and Wushan is 85 mm/d and 80 mm/d,respectively.The recommended value of critical rainfall intensity of Wuxi and Kaixian is (100±5) mm/d.Under the effect of both continuous heavy rainfall and rainfall intensity not less than 30 mm/h,the occurrence probability of hazard is extremely high.The analysis on the situation of geologic hazard induced by heavy rainfall in northeast Chongqing provides technical support for a set of early-warning thresholds and guides the work of disaster prevention and reduction.