Geographia Technica, Vol 21, Issue 1, 2026, pp. 306-322
DEVELOPMENT OF FLOOD RISK MAPS USING AN INTEGRATED HYDRODYNAMIC MODEL AND FAHP IN THE LOWER NAM PHONG BASIN, THAILAND
Chalermchai PAWATTANA, Phaisarn JEEFOO 
, Chaiwiwat VANSAROCHANA , Satit POOPIWKHAM
ABSTRACT: Flooding frequently affects rivers and low-lying areas of the Phong River, making flood risk assessment essential for mitigation and loss reduction. This study developed flood risk maps for the Lower Nam Phong basin using a fuzzy analytic hierarchy process (FAHP) integrated with GIS. Hazard (flood depth, slope, soil drainage) and vulnerability (land use) weights were derived through FAHP. Results show that under baseline conditions, 19.44% of Nong Bua, Bung Nium, and Khok Sri Sub-Districts were classified as high risk, consistent with historical flood records. Future scenarios indicate downstream expansion of high-risk zones: 10.45% under RCP 4.5 (Representative Concentration Pathways) and 12.00% under RCP 8.5, particularly in Bung Nium and Khok Sri. Across all scenarios, medium-risk areas dominated (8.13, 36.45, and 72.67 km2 for baseline, RCP 4.5, and RCP 8.5, respectively). The maps provide actionable insights for flood management and planning in the basin.
Keywords: Climate change; Representative Concentration Pathways (RCP); Flood risk; Fuzzy analytic hierarchy process (FAHP); GIS; Lower Nam Phong basin;
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