Natural-Factor-Based Landslide Vulnerability Assessment Using GIS in Padang Lawas Regency of Indonesia

Abstract

Landslides constitute a major environmental vulnerability in Padang Lawas Regency, where the interaction between steep terrain, heterogeneous geological formations, and intense tropical rainfall frequently drives slope instability. A clear understanding of how these physical factors operate spatially is essential for effective land-use regulation and disaster mitigation. This study develops a natural-factor-based landslide vulnerability assessment using seven key parameters slope gradient, soil type, lithology, rainfall intensity, slope water conditions, seismicity, and vegetation cover. Each parameter was systematically scored and weighted based on its relative influence on slope stability, and a weighted overlay analysis was performed in QGIS to generate a Landslide Vulnerability Index (LVI). Results indicate that moderate hazard dominates approximately 2,028.6 km² of the regency, while high-hazard zones cover 1,128.47 km², mainly concentrated in Sosopan, Ulu Barumun, and Batang Lubuk Sutam Districts. These spatial patterns highlight the combined effects of steep topography, weak lithological units, and high rainfall intensity in governing landslide vulnerability. The outputs provide an empirically grounded basis for strengthening spatial planning policies, guiding infrastructure placement, and enhancing local disaster risk reduction strategies.