Meteorological and vegetation effects on the thermal analysis of slopes

Vegetation affects the water balance in the root zone, leading to changes in pore water pressure in the soil. Despite the tendency of numerical models to overlook the vegetation impact on the soil surface, this study concentrates on creating a unique boundary condition to model the intricate interactions among soil, vegetation, and the atmosphere by considering hydraulic hysteresis. Hence, a boundary condition is integrated into Code_Bright, a finite element program designed for conducting thermo-hydraulic-mechanical simulations, enabling the computation of energy and water balance equations. The canopy resistance formulation is refined through links with solar radiation, vapor pressure deficit, and saturation degree. The model also incorporates a bounding surface approach to capture the hysteretic patterns in soil-water retention curves. The model performance is assessed by monitoring data of a full-scale slope under atmospheric forces for nearly three years. The outcomes demonstrate that the model can reasonably predict the vegetation cover impact on the thermal behavior of slopes. The slope response to rainfall infiltration and its interaction with the atmosphere demonstrated that vegetation plays a significant role in thermo-hydraulic variables. Daily temperature fluctuations are notably intense at shallow depths, particularly within the root zone, while diminishing at greater depths. Due to the incidence angles of solar radiation, the model accurately predicts higher temperatures on south-facing slopes compared to north-facing slopes. In high temperatures and low rainfall durations, the influence of the vegetation layer to develop dryer soil conditions is also more substantial than the slope orientation.