Can One‐dimensional Infiltration Models Reproduce Soil Moisture Variations in Landslide‐prone Hillslopes? Evidence from Petrópolis, Brazil

Abstract The distribution of soil moisture, resulting from the movement of infiltrated water, plays a fundamental role in the hydrological dynamics of hillslopes and in the triggering of landslides. Although water flow in soils occurs in multiple directions due to combined vertical and lateral fluxes, one‐dimensional (1D) flow models are widely adopted as a simplifying assumption in slope‐scale studies, frequently without explicit verification of their validity by researchers. This study evaluates the applicability of the one‐dimensional flow hypothesis under different hydrological conditions and over time. Soil moisture dynamics were simulated using the Hydrus‐1D model, driven by observed precipitation data and calibrated and validated against in situ soil moisture measurements collected at different depths. The results suggest that, at temporal scales associated with rainfall events capable of triggering landslides, one‐dimensional modelling can adequately to represent soil moisture dynamics in slope environments when coupled with measured soil moisture data for the calibration of hydraulic parameters. In contrast, simulations using soil hydraulic parameters estimated from pedotransfer functions showed limited ability to represent the hydraulic behavior of the soils.