This study analyzed satellite images, a digital elevation model, and a digital surface model of the Liukuei Experimental Forest (LEF) to extract indices of vegetation coverage, topographic wetness, and canopy height for obtaining the soil depth index (SDI). Thereafter, a linear relationship was established between the SDI and the
surveyed soil depths (Sd) to estimate the soil depths for the entire forest. Two relationships were determined: that
between the Sd and SDI of the LEF and that of the gradient of the slope with the Sd and vegetation height. By evaluating the relationships and results from other studies, the proportion of vegetation loads to the soil loads was estimated to evaluate the influence of the higher shear stress from the vegetation. Results revealed that when the gradient of slope of the LEF exceeded 55%, the soil depth decreased rapidly as the gradient continued to increase, and the height of the forest canopy also decreased when the gradient of the slope was higher than 84%. Because the ratio of the load of vegetation cover to the load of soil is low on most slopes, the effects of vegetation cover on slope stability outweighed the disadvantages.
Key words: slope stability, soil depth index, canopy height model, Liukuei experimental forest