Physical and socio-economic drought vulnerability in a high-risk local government unit of the Bicol River Basin, Philippines

Climate change–driven drought increasingly threatens water security and community resilience in climate-sensitive watersheds like the Bicol River Basin (BRB) in the Philippines, highlighting the urgent need for sustainable watershed management. This study evaluates the drought vulnerability of selected local government units (LGUs) in water-stressed areas of the BRB. Using a quantitative approach, the research integrates primary data (socio-demographics, water usage, watershed practices) and secondary sources (field observations and literature). A stratified random sampling approach was employed in a March 2025 survey conducted in selected barangays of the BRB, involving 98 household residents (n = 98). Thereafter, 11 indicators across social, economic, and physical dimensions were selected, normalized and weighted using the Analytic Hierarchy Process (AHP) to construct a Physical and Socio-Economic Drought Vulnerability Index (PSE-DVI), categorizing vulnerability into Low (0-0.25), Moderate (0.26-0.50), High (0.51-0.75), and Very High (0.75-1.00) levels. Results indicate that the economic dimension exhibits the highest vulnerability range (0.43–0.99), making it the most influential factor, followed by physical conditions (0.00–0.81). The social vulnerability indicator shows a comparatively moderate range (0.39–0.56). Moreover, clear disparities across the five barangays are observed, with economically constrained and upland communities exhibiting higher vulnerability due to reduced water access, limited infrastructure, and reliance on climate-sensitive livelihoods. To address these gaps, the study proposed an Integrated Watershed Management (IWM) plan that converts assessment results into practical, locally tailored actions to improve drought preparedness and watershed governance.