Development characteristics and genetic mechanism analysis of rainfall-induced loess flowslides in the Dongzhiyuan area

Under extreme rainfall conditions, loess flowslide is widely developed in the loess plateau. Loess flowslides refer to a type of geohazard involving a combination of “flow” and “slide” movements occurring in the unsaturated surface loess on slopes. These events are characterized by their high frequency, shallow failure depths, and widespread distribution. The sliding mass typically exhibits high moisture content and plastic flow behavior, and may evolve into more hazardous and destructive loess mudflows, posing significant threats to life and property in loess regions. In this paper, the rainfall-induced loess flowslide in Qingyang Dongzhiyuan area is taken as the research object. Based on field investigation and UAV survey, 80 detailed flowslide cases were documented and analyzed to summarize their spatial distribution and developmental characteristics. A slope stability evaluation model for unsaturated loess slope was established using the infinite slope model. The results indicate that: (1) Rainfall-induced loess flowslides in the Dongzhiyuan area can be divided into five types: landslide accumulation flowslide, vegetation cover loess flowslide, gully lateral erosion loess flowslide, monomer flowslide, and group flowslide. Group flowslides can be further subdivided into parallel and convergent types based on the relative location of their source areas. (2) These flowslides are generally small in scale due to the terrain constraints of Dongzhiyuan area, often exhibiting low mobility and limited travel distance, making them significantly different from irrigation- or earthquake-induced loess flowslides. (3) A stability evaluation model for vegetation-covered loess slope under unsaturated conditions is proposed, along with integrated mitigation strategies combining engineering, biological, and chemical approaches. These findings offer valuable insights for the prediction of slope stability under rainfall conditions and for the early warning and mitigation of loess flowslide hazards.