Hierarchically measuring urban expansion in fast urbanizing regions using multi-dimensional metrics: A case of Wuhan metropolis, China

Measuring urban expansion is essential for sustainable growth management. However, many widely adopted methods are not suitable for measuring hierarchical urban expansion, particularly in rapidly growing regions. This study provides a framework for hierarchically measuring urban expansion using sub-dimensional, dimensional, and comprehensive metrics. The framework was applied in the Wuhan metropolis (WHM), China, during two 5-year periods from 2005 to 2015. The results show generally improved urban functions and land use conditions in the WHM during the time periods analyzed. However, single period-based sprawl and multi-temporal sprawling patterns remain evident in the WHM as evidenced by decreased accessibility to work opportunities, ecosystem services and natural landscapes, and land use density, as well as disorderly and unplanned land use in certain local areas. Findings derived from the empirical analyses in WHM indicate that the provided framework can demonstrate how gains in certain urban functionality may still occur in regions that have not experienced additional urban land expansion in the WHM. The framework is suitable for hierarchically measuring urban expansion in rapidly urbanizing areas exhibiting multi-temporal, mixed expansion patterns. The hierarchical framework and findings provided in the study contribute to urban expansion measurement and management in the WHM as well as other rapidly urbanizing regions around the world.