Land-Use Change and Watershed Degradation: A GIS-Based Assessment of Environmental Transformation in Rapidly Urbanizing Regions

Abstract

Rapid urbanization alters watershed structure and water quality through the expansion of developed land, impervious surfaces, and associated hydrological disturbances. This retrospective ecological study assessed land-use change and watershed degradation across 38 exurban, suburban, and urban watersheds in the Atlanta metropolitan region from 2014 to 2021 using geographic information system data, watershed characteristics, and multiyear water-quality records. Developed-land change, imperviousness, urban land use, population density, housing density, high-intensity development, and forest cover were integrated into an Environmental Transformation Index, whereas conductivity, temperature, turbidity, dissolved oxygen, and pH were combined into a Watershed Degradation Index. Group differences were tested using the Kruskal–Wallis test, associations were examined using Spearman's rank correlation, and robust regression and mixed-effects models were applied. Developed-land expansion was greatest in exurban watersheds, whereas urban watersheds had the highest imperviousness, urban land use, conductivity, temperature, and degradation scores. The Environmental Transformation Index correlated positively with conductivity, temperature, and watershed degradation, while developed-land change was positively associated with turbidity. Forest cover was inversely associated with conductivity. Temporal models showed limited annual change in most indicators, although urban watersheds consistently maintained higher conductivity. GIS-based integration identified a transition from newly developing peripheral watersheds to cumulatively degraded urban systems, supporting targeted stormwater management, riparian protection, land-use regulation, and watershed-specific environmental planning.