Dynamic variations of interception loss-infiltration-runoff in three land-use types and their influence on slope stability: An example from the eastern margin of the Tibetan Plateau

Abstract

Hydrological processes in slopes play an important role in the evaluation of slope stability at the catchment scale. This study investigated the dynamic variations of interception loss-infiltration-runoff in three land-use types (bare slope and slopes with C. dactylon and I. amblyantha cover) for incident rainfall and their influence on slope stability. Gross rainfall, surface runoff, and subsurface flow were measured during the rainy season in 2020, and the influences of rainfall characteristics (rainfall amount and intensity) and slope gradients on canopy interception loss, water infiltration, and surface runoff were evaluated. On this basis, a model considering infiltration zonation was adopted to estimate slope stability under the influence of infiltration modified by vegetation. Field test results showed that runoff on bare slope generally occurred following rainfall events with amounts of > 6.1 mm or intensities of > 7.2 mm h−1. For slopes covered by C. dactylon and I. amblyantha, the thresholds of rainfall intensity for runoff generation were 25 mm h−1 and 36 mm h−1, respectively. The calculated relative interception loss for the slope with C. dactylon cover stabilized at 0.05–0.10 when the rainfall amount was > 18 mm, while that for the slope with I. amblyantha cover stabilized at 0.10–0.15 when the rainfall amount was > 30 mm. Moreover, the slope with C. dactylon cover appeared to have a higher proportion of infiltration than that with I. amblyantha cover. The stable infiltration rate in the three land-use types decreased gradually with increasing slope gradient, whereas an opposite pattern was exhibited for the stable runoff intensity. The influence of the morphological features of plant species on the variation of interception loss-infiltration-runoff weakened as slope gradient increased. The modeling results demonstrated that the depth of the wetting front was negatively correlated with slope gradient and followed a quadratic function with rainfall intensity. Based on the computed safety factor at the wetting front, the critical times of slope instability follow the order of bare slope (46.2 min) > I. amblyantha slope (34.8 min) > C. dactylon slope (30.5 min). The modification of infiltration by plants accelerated slope instability, with potential reductions in the safety factor by 15.9%–53.1%. Slope gradient plays a dominant role in slope stability, and the influence of modified infiltration on slope stability weakens with increasing slope gradient. Those findings provide valuable information for the decision makers concerned with planting I. amblyantha in the subtropical region to reduce peak flood discharge and prevent slope instability.