Pengaruh Perubahan Penggunaan Lahan dan Fragmentasi Lanskap terhadap Transformasi Hujan–Limpasan di DAS Ake Kobe

Abstract

Land-use change and landscape fragmentation may alter rainfall–runoff responses in tropical watersheds, although their combined hydrological implications remain insufficiently characterised. This study assessed land-use transitions, landscape configuration, Curve Number (CN) patterns, and modelled surface runoff in the Ake Kobe Watershed, Indonesia, during 2020–2024. Sentinel-2 imagery was classified using Random Forest, land-use transitions were visualised through Sankey diagrams, and landscape metrics were calculated using FRAGSTATS. Spatial CN distributions were derived from land use and hydrological soil groups using GIS and HEC-GeoHMS. Surface runoff was estimated with the Soil Conservation Service–Curve Number method and CHIRPS rainfall data. Forest cover declined from 85.97% to 82.79%, while mining and bare land expanded. Landscape division increased from 0.2956 to 0.4429, and contagion declined from 84.3659 to 79.6620, indicating greater fragmentation and reduced spatial aggregation. Areas with CN values of 84–98 expanded from approximately 2% to 8%. Mean estimated runoff increased from 173.599 to 220.060 mm (26.8%), alongside increased rainfall. These findings demonstrate concurrent changes in land cover, landscape structure, and modelled runoff, without isolating their individual causal contributions. The integrated framework supports spatial prioritisation of watershed conservation, rehabilitation, and hydrological risk management in tropical catchments, particularly where forest conversion and extractive activities increasingly threaten ecosystem integrity