Improved Method of Defining Rainfall Intensity and Duration Thresholds for Shallow Landslides Based on TRIGRS

Abstract

The Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model has been widely used to define rainfall thresholds for triggering shallow landslides. In this study, the rainfall intensity(I)-duration(D) thresholds for multiple slope units of an area in Pu’an County, Guizhou Province, China were defined based on TRIGRS. Given that TRIGRS is used to simulate the slope stability under the conditions of a given increasing sequence of I-D data, if the slope reaches instability at I = a, D = b, it will also become unstable in the case of I = a, D > b or I > a, D = b. To explore the effect of these I-D data with the same I or D values on the definition of I-D thresholds and the best method to exclude these data, two screening methods were used to exclude the I-D data that caused instability in the TRIGTS simulation. First, I-D data with the same I values when D values are greater than a certain limit value were excluded. Second, several D values were selected to exclude I-D data with the same I values for a slope unit. Then, an I value was selected to exclude I-D data with the same D values. After screening, two different I-D thresholds were defined. The comparison with the thresholds defined without screening shows that the I-D data with the same I or D values will reduce the accuracy of thresholds. Moreover, the second screening method can entirely exclude these data.

Influence of soil mechanical and hydraulic parameters on the definition of rainfall intensity and duration thresholds based on Transient rainfall infiltration and grid-based regional slope-stability model (TRIGRS)

“…This study defined rainfall thresholds using the a c of 1%. Before fitting, the I-D conditions that cause instability were screened to exclude the I-D conditions with the same I or D values (Zhang et al, 2022). Then, the screened I-D conditions were plotted in a log-log plot (logI vs logD).…”

“…In this study, the method proposed by Zhang et al (2022) was used to define I-D thresholds at the slope unit scale. The slope units were delineated based on ridge and valley lines obtained by using hydrology analysis tools in ArcGIS.…”

Definition of hydro-meteorological thresholds for landslides based on a limited dataset

“…Rainfall thresholds are typically defined based on two approaches: statistical and physically-based ones. Physically based ones are commonly employed at small watersheds or slopes due to the challenge of obtaining detailed soil parameters necessary to simulate slope stability during rainfall infiltration over large areas [4][5]. In contrast, statistical ones are most used because they just require the historical rainfall conditions induced landslides.…”