Segmentation Method Study About The Antecedent Precipitation When Debris Flow Stimulated

Storm debris flow is a common geological hazards on slopes or valleys,It triggered by the excitation of external conditions such as rainstorm,usually with fast speed of the movement,sudden occurrence,enormous energy.It consists two stages,firstly soil in the ravine is saturated after water uptake by rainfall,after the shallow soil water saturated,excitation rainfall becomes becomes surface runoff subsequently,the runoff collected and bottom tearing the saturated soil becomes debris flow.Warning and forecast the storm debris flow by monitoring and analysize the antecedent precipitation and excited rains mainly.The distinction of antecedent precipitation has a major impact on storm debris flow warning and forecast,in this regard,many scholars studied,Huang ting hui study many times debris flows evoked by strong typhoon in Taiwan,Put forward that when rainfall intensity continuous 6h is not less than 4mm / h,it can be regarded as the beginning of the eantecedent precipitation.Zhou Wei Studied the early rainfall and stimulate rainfall of the debris flow gully after Wenchuan earthquake in Wenchuan county,He thought when rainfall intensity continuous 6h is not less than 1mm / h,it can be regarded as the beginning of the antecedent precipitation.These two methods through study a particular area of debris flow,then obtain segmentation method.For example Huang ting hui obtain the segmentation method through storm debris flow which caused by the typhoon,it maybe applicable in Taiwan,however may not be applicable in other places.Zhou Wei obtain the segmentation method through analysize debris flow gullies in strong earthquake zone,so there are certain limitations.This paper through analysized field rainfall data and existing segmentation method,use indoor test method simulate the process of infiltration and runoff stage when soil slope in rainfall,then determine the segmentation method about antecedent precipitation.Choose slope,topography,rainfall intensity,vegetation cover four factors as influential factors about rainfall infiltration and runoff.Use slope runoff time and pore pressure analysis the process of infiltration and runoff.through experiments get the following conclusions:(1)The gradient is the important factor that affects the runoff of the slope.The steeper slope gradient,the more easy runoff,the slower the slope,the more unfavorable to the runoff of the slope.(2)Topography is an important factor that affects the runoff of overland flow.The more terrain changes,the more unfavorable to runoff,the smaller the terrain changes,and the more benefit to runoff.(3)The vegetation cover rate is the important factor that affects the runoff,the higher the vegetation cover,the less runoff,the lower the vegetation cover,the more benefit to produce the runoff.(4)The rainfall intensity has an important effect on the overland flow time,rain intensity more runoff,rainfall runoff is not conducive to more small.(5)For the bare slopes,the rain intensity was greater than 1mm/h for the rainfall,when the rain intensity of the rain was less than 6h or 8mm accumulated within 1mm/h or 12 h,as the end of the rainfall..(6)For good slope vegetation cover,when the rainfall intensity is larger than 2mm/h as the rain began to,when the continuous 6h rainfall intensity is less than 2mm/h or 12 h cumulative rainfall less than 12 mm,depending on the end of the rainfall.(7)With three regional rainfall data and the prediction method of existing research results and the research methods are validated by,the research methods appear lower the possibility of error and the possibility of underreporting is low.