DELINEATION AND IDENTIFICATION OF RIVER BASIN WATERSHED FORMS USING GEOGRAPHIC INFORMATION SYSTEMS AND REMOTE SENSING

Abstract

Based on data from the Central Statistics Agency (BPS) in 2024, in the last three years there have been 62 floods in East Aceh Regency, Langsa City, and Aceh Tamiang Regency, with details of 29 incidents in East Aceh, 13 incidents in Langsa City, and 20 incidents in Aceh Tamiang. The high frequency of flooding indicates the need for hydrological studies in the Krueng Bayeun, Krueng Langsa, and Krueng Tamiang River Basins (DAS). This study aims to analyze watershed boundaries, topographic characteristics, and the shape and pattern of river flow direction using a Geographic Information System (GIS) based on Digital Elevation Model (DEM) data. The study was conducted using a quantitative descriptive survey method through remote sensing analysis. The results of the Spatial Analyst Hydrology analysis show that the watershed area is depicted in the form of a polygon as the main watershed area. The roundness ratio values ​​of the Krueng Bayeun, Krueng Langsa, and Krueng Tamiang watersheds are 0.23; 0.30; and 0.34, respectively, indicating that the three watersheds are elongated. Water flow is focused toward low-lying areas, potentially increasing water accumulation and the risk of flooding, especially during the rainy season. All three watersheds are dominated by dendritic drainage patterns with moderate river density, indicating sufficient water reserves. The Krueng Bayeun and Krueng Langsa watersheds are dominated by flat to gentle slopes, resulting in slower river flow and longer retention of standing water. Meanwhile, the Krueng Tamiang watershed is dominated by steep to very steep slopes, accelerating flow, increasing erosion, and potentially causing flooding in downstream areas.