Geological feature and rainfall threshold of cluster landslides along roads toward Tibet in Gongshan County,Yunnan Province,China
Rainfall-induced landslides along roads towards Tibet are frequent in Gongshan County,Yunnan Province.Cluster landslides were triggered herein by the heaviest rainfall since the meteorological record in May,2020.Aiming at studying the geological features of these landslides,establishing rainfall threshold and early warning method,the distribution characteristics of cluster landslides were analyzed under the condition of different geological environment factors based on ArcGIS platform.The method for establishing rainfall threshold and cumulated probability early-warning curve based on Bayesian inference method and Kernel Density Estimation were developed.The rainfall intensity-duration threshold curves of road landslides close to Gongshan County under different shortest rainless interval times(SRIT)were established and discussed.The results demonstrate that the cluster landslides sliding in shallow layer are caused by the extreme rainfall characterized by the strongest continuity,fastest growth rate and highest peak intensity during the same period of 2004-2020.Size parameter α and shape parameter β of rainfall threshold decrease with increasing of SRIT.An upper limit of SRIT for establishing rainfall threshold exists in a specified region,when its value exceeded the variability of rainfall threshold is more significant.The rainfall intensity is more important than duration for road landslide triggering in Gongshan County.The established methods for rainfall threshold and early-warning are reasonable and objective.The SRIT of 12 h(dry season)+24 h(rainly season)is more suitable for establishing rainfall threshold of Gongshan County.
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