Hydrological Response and Flood Potential Assessment of a Tropical Small Island: Integration of Geomorphometric Indices and Water Balance in Wai Ruhu Watershed, Ambon, Maluku, East Indonesia
Keywords:
Geomorphological indices, Water balance, Flood potential, Small tropical islands, Wai Ruhu WatershedAbstract
High annual rainfall on Ambon Island significantly increases its vulnerability to hydrological disasters, particularly flooding. This study evaluates flood potential in the Wai Ruhu Watershed by integrating geomorphometric indices with water balance analysis. Geomorphological characteristics, including stream order, bifurcation ratio (Rb), drainage density (Dd), form factor (Rf), circularity ratio (Rc), and elongation ratio (Re), were analyzed using ArcGIS 10.8. The water balance was determined using 11 years of precipitation and evapotranspiration data (2014–2024), while surface runoff and infiltration were estimated based on land cover and slope gradients. The results indicate that the watershed’s low bifurcation ratio and moderate-high drainage density reflect a rapid hydrological response and strong structural control on flow. Furthermore, steep topography and land cover changes significantly increase the runoff coefficient, leading to high surface discharge and limited infiltration. The integration of these parameters confirms a high flood risk, particularly in densely populated downstream areas. These findings provide a critical framework for watershed management and land-use planning to mitigate hydrological hazards in small tropical island environments such as Ambon City.
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