Construction land expansion and influencing factors of typical river valley cities in Northeast China: Taking Jilin City as an example

Jilin City is a typical river valley city in Northeast China. In this paper, the authors studied the spatial and temporal expansion characteristics of the built-up areas in Jilin City from 1990 to 2020 using the analysis of expansion speed and strength, fractal dimension, barycenter coordinate transfer index and sector analysis. The ultimate-goal is to analyze the driving and restrictive factors that affect the spatial expansion of river valley cities. The results indicate that (1) the expansion speed of urban land in Jilin City has been relatively slow in the past 30 years, while only slightly faster in 2010–2020; (2) in the spatial dimension, Jilin City mainly expanded to the south, then to the west, and extensive expansion has resulted in complex morphology with little stability and compactness; (3) the expansion is affected by multiple factors, of which the positive factor is industrial development, while the restrictive factors include natural factors, population loss, etc. This study provides a case for the formulation of land use policies and land space planning in river valley cities.