基于土壤侵蚀模型的滑波临界雨量估算探讨

STUDY OF ESTIMATING CRITICAL RAINFALL OF LANDSLIDE BASED ON SOIL EROSION MODEL

针对滑坡临界雨量确定目前存在的问题,提出一种基于土壤侵蚀模型的滑坡临界雨量估算的新方法。该方法基本思路是:降雨引起土壤侵蚀,当土壤侵蚀达到一定强度时可诱发滑坡,因此利用土壤侵蚀模型可以推算滑坡临界雨量。以湖北省秭归县为例进行试验,从降雨-土壤侵蚀-滑坡的成灾机理入手,利用卫星资料、地理信息资料及降雨资料,计算降雨侵蚀力、土壤可蚀性、地形(坡长、坡度)、植被覆盖和土地利用类型等因子,基于USLE土壤侵蚀模型,计算滑坡发生时土壤侵蚀强度,通过分析多个滑坡个例,确定滑坡临界土壤侵蚀强度,再根据降雨侵蚀力与降雨量之间的关系,推算不同预警点滑坡临界雨量。相比以往仅仅分析灾情与降雨之间关系的传统方法,该方法有较为清晰的物理意义,实际业务中也易于实现,在滑坡预警预报中有较高实用价值。

Landslide,which is mainly due to rainfalls,is one of the most harmful geological disasters.The key issue of the early warning and forecast of landslide is to determinate the landslide hazard formative critical rainfall with the traditional method of statistical analyses between disaster and rainfalls.However,these methods always ignore some factors affecting landslide disaster including vegetation cover and geological condition and determinate the landslide hazard-formative critical rainfall only standing for a value for regional average but not for a concrete landslide point.Soil erosion caused by rainfall would lead to landslides when it reaches a certain intensity.Therefore,it is feasibility to determinate of landslide hazard formative critical rainfall on the basis of soil erosion model.In view of the problems in existing researches and the hazard-formative mechanism of Rain-Soil erosion-Landslides,a novel method based on soil erosion model was tried out in Zigui county of hubei province with the following steps.Firstly,various factors including rainfall erosivity,soil erodibility,topographic conditions,such as slope length and slope gradient,vegetation cover and land use types are calculated by employing remotely sensed data,geographic information data and meteorological rainfall data.Secondly,several landslide cases were analyzed using USLE(Universal Soil Loss Equation)soil erosion model to determinate the soil erosion intensity for landslide critical.Thirdly,the hazard-formative critical rainfall amount of the landslide warning sites was calculated on the basis of the relationship between the rainfall erosivity and rainfall amounts.Finally,those determined values of landslide hazard-formative critical rainfall were accurately tested.Conclusively,the method based on soil erosion model is feasible to determinate landslide hazard-formative critical rainfall.The proposed method shows a clear physical meaning with the considerations of various affecting factors including rainfall,vegetation cover and geological condition for landslide and easy implementation in practical work,thus has a highly practical value in the landslide early warning and forecast.