GIS AND AHP-BASED FLOOD ZONING AND CONSERVATION STRATEGIES IN THE TARUSAN WATERSHED, INDONESIA

Eri BARLIAN , Iswandi UMAR , Indang DEWATA , Triyatno TRIYATNO , Aprizon PUTRA , Eva MUSTIKASARI , Sri Endah PURNAMANINGTYAS , Erfan Andi HENDRAJAT , Serly Mutia SARI , Yulius YULIUS , Dewi Rahmadani SIREGAR

DOI: 10.21163/GT_2025.202.08

ABSTRACT: This study aims to identify flood hazard zones and formulate flood disaster mitigation strategies through an integrated watershed conservation framework in the Tarusan Watershed, Pesisir Selatan Regency, West Sumatra, Indonesia. This study applied a Geographic Information System (GIS)-based spatial analysis combined with the Analytical Hierarchy Process (AHP) method to map flood hazard zones and prioritize flood mitigation strategies. Flood hazard assessment was carried out using six indicators (rainfall, slope, landform, land use, soil type, and geological formation). Flood hazard zones were classified into three categories (low, medium, and high) based on a composite scoring system ranging from 65 to 325. The results indicated that the high flood hazard zone (22%) was concentrated in the downstream areas, influenced by flat slopes, high rainfall, alluvium deposits, and intensive human activities. Medium hazard zones (58%) were found in the midstream areas, while low hazard zones (20%) were located in upstream regions with steep slopes and dense forest cover. The AHP analysis involved 25 experts from diverse institutions, identifying seven strategic alternatives categorized into three main priorities: regulation, education, and institutional strengthening. The most dominant strategy was increasing community knowledge about forest functions (weight 0.301), followed by strengthening local institutions (0.149), and improving collaboration with government agencies (0.149). Integration between flood hazard zoning and AHP-based strategies shows that upstream areas require forest conservation and environmental education, midstream areas need sustainable livelihood development, while downstream areas demand regulation enforcement and improved land-use control.

Keywords: Flood Hazard; Watershed Conservation; Analytical Hierarchy Process (AHP); GIS-Based Analysis; Tarusan Watershed

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