Ilham Alimuddin

Landslides pose a significant threat to the Tapalang District in Mamuju, because of its geographical conditions, steep slopes, high rainfall intensity, and frequent seismic activity. This study aims to analyze the Landslide Hazard Index (LHI) in the region using Geographic Information Systems (GIS) and the Analytical Hierarchy Process (AHP) to determine the spatial distribution of the landslide risks and identify high-risk zones. The methodology incorporates topographical, geological, land use, soil type, and rainfall data, assessed through an AHP-based multi-criteria analysis, and mapped using GIS tools to create a comprehensive landslide susceptibility map. The results indicate that Tapalang District shows different levels of landslide susceptibility, with high-risk areas primarily found in regions featuring steep slopes, loose soil composition, and notable land-use changes. Moderate-risk zones encompass a significant portion of the district and necessitate ongoing monitoring, whereas low-risk areas are largely situated in flatter, more stable regions. The novelty of this study lies in the integrated use of GIS and AHP to improve the accuracy of landslide risk assessment by offering a quantitative and spatially detailed risk classification. This innovation provides a replicable and scalable decision-support model for local governments and disaster management agencies to develop proactive mitigation strategies, including early warning systems, land-use regulation enforcement, and slope stabilization measures. This research contributes to disaster management planning by providing a robust framework for assessing and mitigating landslide hazards in Tapalang and other similarly vulnerable regions.

One important factor that influences the optimization of the formation of nickel laterite deposits is the slope of a region's topography. The Mangguruh area in Sebuku Island in South Kalimantan is composed of ultramafic rocks on a gently flat topography but forms laterite deposits of varying thickness. Based on the exploration data from 33 drilling points and field data acquisition, this study aims to: 1) create topographic slope groups with varying ranges to determine the range most suited to real conditions in the field, 2) determine the laterite thickness, 3) analyze the concentration of Ni and Fe in limonite and saprolite layers, 4) analyze the effect of topographic slope to the laterite thickness. The method used is the measurement of topographic slope in the field with compass and using ArcGIS software applications in preparing the maps, analyzing laterite profiles from the drilling data and sampling rocks and ores. The study performed a laboratory analysis consisting of petrographic analysis and X-ray Fluorescence testing of the elements. The result revealed that the appropriate topographic slope groups in the study area were 0-5%, 5-10%, 10-15% and ≥ 15%. The laterite thickness of > 10m lied on the slope of 0-5% and 5-10% and contains a moderate-high nickel content of 1.2% -> 1.4%. This indicates that laterite nickel enrichment is influenced by topography. While the distribution of iron ore with medium and high levels of concentration (45-50% and > 50%) has commonly occurred in each topographic slope group indicating that topography is less influential on the distribution of iron ore. Earlier research has indicated that effect of topography on different morphologies is clear and many of the studies were conducted on a regional scale, but interestingly in Sebuku area, the topography is gently flat but the thickness and nickel content is varied. So the results of this study can be applied to slightly flat slope areas and therefore needs more detailed mapping.