山火后首次泥石流预警

On Early Warning of First Debris Flow after a Wildfire

火后泥石流是一种易发且破坏力强的灾害,是山区开展防灾减灾的重要对象.国外研究火后泥石流预测模型只针对数据库所在的区域预测效果良好,对其他地区的预测结果不理想.森林火灾会造成林下土壤斥水性显著增强,发生降雨时,极易形成大流量山洪,诱发泥石流.在山火后的第一个雨季泥石流发生的降雨阈值很低,泥石流发生概率很高.选择四川凉山州发生的山火为研究案例,提出等效前期降雨量概念,并通过野外人工降雨实验,建立等效前期降雨量计算模型,结合常规泥石流预警公式建立沟床起动类型的火后首次泥石流的预警模型,在国内凉山、甘孜地区和美国地区的火后首次泥石流案例中,验证了方法的可靠性,为火后泥石流的减灾防灾提供一种新的方法.

Postfire debris flows are hazards that can easily occur and are highly destructive,making them an important target for hazard prevention and mitigation in mountainous areas.Postfire debris flow prediction models developed by researchers outside China offer good prediction results only for regions corresponding to the databases used but poor prediction results for other regions.A forest fire can significantly increase the water repellency of the soil under the forest,and when rainfall occurs,flash floods with high flows form very easily and trigger debris flows.In the first rainy season after a wildfire,the rainfall threshold for debris flow occurrence is very low and the probability of debris flow occurrence is very high.Using wildfires in Liangshan Prefecture,Sichuan Province,China,a concept of equivalent antecedent rainfall(EAR)was introduced,and an EAR calculation model was established through artificial rainfall experiments.An early warning model for the first postfire gully-type debris flow was established using the general quation.The reliability of the method was verified using initial postfire debris flow events in Sichuan,China,and in the United States.The early warning model for first postfire debris flow in this study is a new method for hazard mitigation and the prevention of postfire debris flows.