Pengaruh Kondisi Vegetasi dan Geologi Terhadap Gerakan Tanah Dengan Pemicu Hujan

Abstract

The objective of this study was to analyze the role of vegetations in controlling rain-induced landslides. Slope stability analysis based on limit equilibrium concept was adopt to execute such analysis. Numerical model by applying COMBINED HYDROLOGY AND STABILITY MODEL (CHASM) was applied to simulate the changing of slope stability in response to rain infiltration under the control of specific vegetation types. Three different slope models consisting of bedrock of andesitic breccia overlain by clay with various slope inclinations, 15°, 30° dan 45° were selected to be subjected to the various rain intensity of 20 mm/ day, 50 mm/ day, 100 mm/ day dan 160 mm/day. The simulation results showed that bamboo, cassava, paddy (without irrigation) and vetiver significantly prevented the rain-induced landslides only on the gentle slope (being less steep than 45°). In the slope which was steeper than 45° roles of slope inclination and stratigraphy as well as geotechnical properties of rock/ soil forming the slope were more significant than the role of vegetation in controlling slope stability. It was also apparent that paddy with irrigation significantly reduced the slope stability on gentle slope (15°), despite only low rain intensity (20mm/day) applied. Indeed, the rainfall had no important role in inducing landslide on such gentle slope. Those simulation and analysis results were also evaluated by comparing to the real rain-induced landslide cases occurring in several sites in Indonesia