Identification of Mass Movement Susceptibility Zones Using Geotechnical Investigation and the Weight of Evidence (WoE) Method in Sambutan District, Samarinda, East Kalimantan

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Abstract

The Sambutan District in Samarinda, East Kalimantan, has a hilly terrain with varying slopes and mainly consists of soft sedimentary materials, making it prone to landslides. Without prompt management, these landslides could cause significant damage. This study aims to identify high-risk landslide areas in Sambutan District to guide authorities in implementing mitigation measures and minimizing potential losses. The research combined field surveys and laboratory tests, including Cone Penetration Tests (CPT) at key points to evaluate soil stratigraphy and strength through cone resistance. These findings were correlated with physical soil analyses, which measured water content, specific gravity, bulk density, and Atterberg limits (liquid, plastic, and shrinkage limits). A direct shear test was also conducted to determine soil shear strength parameters, cohesion (c) and internal friction angle (φ), to assess slope stability using the safety factor (FK). Based on these tests, landslide risk was categorized into low, medium, and high, considering factors like slope angle, height, direction, rainfall, soil type, proximity to rivers and roads, as well as NDVI, NDBI, land cover, and slope curvature. These factors were analyzed with the Weight of Evidence (WoE) method. Results indicate that slope, soil type, and elevation are the most influential parameters for landslides. High-risk areas extend northward, then south, with additional zones in the northwest, southwest, and a small eastern section. Laboratory results show that soft soils, such as clay with moderate to high plasticity, are common in landslide-prone zones. The greater the soil plasticity, the higher the landslide risk. These findings provide a scientific basis for government policies and spatial planning aimed at targeted mitigation efforts to prevent further damage losses.