Integrated spatial analysis of drought risk factors using agglomerative hierarchical clustering and correlation

Abstract

Drought results from the complex interplay between climatic variability and human activities, further intensified by hydro-meteorological and socio-economic interactions. This study investigates the interrelationships among climatic, geographic, soil, and anthropogenic factors influencing drought risk in the Upper Phetchaburi River Basin. Ten key drought risk factors—precipitation, aridity index, slope, elevation, soil texture, drainage, fertility, erosion, land use, and land cover—were spatially analyzed using Agglomerative Hierarchical Clustering and Pearson Product-Moment Correlation. The analysis revealed both direct and inverse relationships among these variables, underscoring the compounded effects of climate, land use, and soil dynamics on drought vulnerability. A particularly strong correlation between climatic and anthropogenic variables suggests a spatial-temporal alignment that intensifies drought conditions. Additional significant correlations—including precipitation–aridity index, aridity index–land use, and slope–soil fertility—further emphasize the integrated nature of environmental processes regulating drought susceptibility. Clustering analysis identified three distinct groups: (1) precipitation, aridity index, and soil erosion, illustrating how reductions in precipitation and aridity index accelerate soil degradation; (2) soil properties—texture, drainage, and fertility—are crucial in highlighting their roles in water retention, nutrient availability, and vegetation resilience, particularly in slope terrain; and (3) elevation, land use, and land cover, demonstrating the combined effects of topography and anthropogenic activities on drought dynamics. These findings underscore the urgent need for sustainable land management, targeted ecosystem restoration, and climate-adaptive policies to mitigate drought risks. By elucidating localized drought drivers within broader environmental contexts, this study offers a transferable framework for informing proactive, cross-disciplinary drought mitigation strategies.