Beyond expansion: impervious surface reversals in Zhengzhou, China

Urban land-use/cover change research has long neglected impervious surface (IS) reversals, resulting in an incomplete understanding of urban land transitions. Using Zhengzhou as a case, this research utilised annual Landsat TM/ETM+/OLI images (2000–2020) to extract 30 m-resolution IS percentage data. Based on this precise dataset, three IS change patterns were defined: IS expansion (ISEX), IS intensification (ISIN), and IS reversal (ISRE) to characterize the spatiotemporal dynamics and quantitatively examine their trends. Our study shows that the total IS area increased, while IS density decreased. ISIN contributed more to IS growth than ISEX, with both accelerating toward the southeast. A notable upward trend in the total ISRE area was observed, primarily clustered in core urban areas. Land use policies mainly influence the complex spatiotemporal variations in IS in Zhengzhou. Overall, accelerating IS growth dominates the megacity, but ISRE, critical for urban redevelopment under construction land inventory policies, should not be ignored.