Long-Term Seepage and Stability of Tropical Railway Cut Slopes Using Satellite Hydroclimatic Data

Abstract Rainfall-induced landslides threaten tropical railway infrastructure, where sparse monitoring limits the characterization of rainfall–instability relationships. This study investigated the long-term hydraulic response and stability of railway cut slopes in residual soils along a strategic railway in the Brazilian Amazon using alternative climate datasets. Satellite-derived precipitation (CHIRPS), satellite-informed soil moisture (SMAP), and gridded meteorological variables (BR-DWGD) were integrated with laboratory hydraulic relationships and field groundwater observations to define atmospheric forcing and initial hydraulic conditions. Daily sequential seepage–stability simulations spanning more than 40 yrs were performed for four representative slope inclinations. Increasing inclination reduced stability, and only the 40° slope exhibited simulated instability. Mean annual precipitation was highest during La Niña, intermediate during neutral conditions, and lowest during El Niño, whereas mean annual minimum factor of safety (FoS) followed the reverse ordering across all inclinations. Statistically significant differences supported an association between El Niño–Southern Oscillation variability and simulated stability. Mean monthly minimum FoS was lowest in April for steeper slopes, consistent with cumulative wet-season infiltration and broadly aligned with reported March–April slope-instability events along the railway. A criterion combining 7-, 15-, and 90-day rainfall accumulations provided a preliminary model-derived reference for investigating simulated instability. The underlying mechanisms involved matric suction dissipation and localized groundwater rise near the toe, without requiring full saturation of the overlying soil. Hydraulic contrasts can guide instrumentation placement. The framework supports slope screening for railway asset management and preliminary assessment of stabilization measures, providing a basis for subsequent site-specific investigation, calibration, and design refinement.