Analysis of the evolution characteristics and driving factors of the three-dimensional morphology of the city space: A case study of Wuhan Main Urban Area

Objectives: To analyze the evolution of Wuhan's three-dimensional urban space and identify its driving factors to help solve urban problems caused by rapid expansion. Methods: The traditional architectural landscape indicators were used to analyze the general three-dimensional space structure of Wuhan from 2000 to 2018. An improved VHG ratio was then introduced to more accurately detect whether horizontal or vertical scale expansion occurred during the corresponding year interval. Finally, we employed a random forest model to construct a nonlinear model to identify the driving factors that have led to the current status of the city's three-dimensional space. Results: From 2000 to 2018, traditional architecture landscape indicators show that the city of Wuhan underwent an expansion in the three-dimensional city space features, and the construction of a large number of residential buildings is the direct cause of this situation. The improved VHG ratio indicates that the main urban area of Wuhan underwent significant vertical space expansion. In addition, our study reveals that subway and railway stations have played a significant role in driving the vertical scale expansion of the city's three-dimensional space. Conclusions: Our research successfully identified the evolution characteristics of the three-dimensional morphology of urban space in Wuhan and the driving factors behind it. The methods we used in this study, including traditional architectural landscape indicators, improved VHG ratio, and random forest model, can be applied to other cities to provide insights into their three-dimensional urban space evolution.