Modeling the spatiotemporal heterogeneity and changes of slope stability in rainfall-induced landslide areas

Rainfall-induced landslides are sudden, widespread, and prone to cause significant loss of life and property. To explore the heterogeneity and changes in slope stability under extreme rainfall conditions, we took Yongtai County, Fuzhou City, as the study area, and focused on the impact of rainfall on slope stability during the "7·9" extreme rainstorm event in 2016. Regional data on topography, geotechnical engineering, hydrogeology, and precipitation were collected through field sampling, site monitoring, and public datasets. The collected data, after preprocessing, were used to build the TRIGRS (transient rainfall infiltration and grid-based regional slope stability) model for evaluating the regional slope stabilities during the event. Finally, the local spatial and temporal effects of rainfall on slope stability were analyzed by using the STWR (spatiotemporal weighted regression) model. Results show that: (1) Most areas in Yongtai County was safe during the event (most of the factor of safety (FS) were higher than 1.5), but as the duration of rainfall increased, the FS of some grids in the study area continued to decline, the unsafety areas were gradually expanding, and some areas were still at risk of landslides. (2) The spatial variation of slope stability in Yongtai County was great, with characteristics of low in the center and high in the east and west. High-risk areas were concentrated in the northwest of Qingliang Town, and the south of Songkou Town. Southeast of Dayang Town and Baiyun Town. (3) The impacts of rainfall on slope stability were spatiotemporally heterogeneous. In terms of time, rainfall negatively impacted slope stability and continued to show an enhancing trend as the duration of rainfall increased. In terms of space, the affected area showed an expanding trend as the rainfall continued, expanding from the towns of Hongxing, Fukou, and the northeastern part of Geling to the towns of Songkou, southeastern Wutong, eastern Chengfeng, and southern Chixi, etc. Overall, our study fills the insufficiency of the spatiotemporal heterogeneity analysis on the impact of rainfall on slope stability of landslides, which can provide some reference for shallow landslide risk management and disaster early warning.