The influence of the rainfall data temporal resolution on the results of numerical modelling of landslide reactivation in flysch slope

There are numerous examples in the literature where numerical modelling has been used as a valuable tool in the study of rainfall-induced landslides. While much attention has been paid to the influence of different rainfall characteristics and patterns, spatial variability or temporal patterns of rainfall intensity, very little attention has been paid to the influence of the temporal resolution of rainfall data used in numerical simulations of rainfall infiltration and slope stability analysis. This is particularly true for deep-seated landslides occurring on slopes composed of soils with relatively low hydraulic conductivity, as in the case of flysch deposits presented in this study. A recently developed 2D numerical model is used to investigate the results of transient infiltration and slope stability analysis for flux boundary conditions derived from three temporal resolutions of realistic rainfall data: (i) 10-min, (ii) hourly and (iii) daily rainfall measurements. The results obtained show that deriving the time-dependent flux boundary conditions using the coarse resolution rainfall data (e.g. daily rainfall measurements) can lead to a calculation of unrealistically high infiltrated volumes, a faster increase in water content and pore water pressure in a slope cross-section, and a reduction in the factor of safety at an unrealistically high rate, resulting in a conservative prediction of the time to slope failure. The results suggest hourly rainfall data as the optimal form of input data for the case study under investigation.

Automated summary

Numerical modeling has been widely used in studying rainfall-induced landslides, but the influence of temporal resolution of rainfall data in the simulations has received little attention. This study investigates the effects of different temporal resolutions of realistic rainfall data on infiltration and slope stability analysis using a 2D numerical model. The results show that using coarse resolution rainfall data can lead to unrealistically high infiltrated volumes and a conservative prediction of slope failure time, suggesting hourly rainfall data as the optimal input for the case study.