Integrating blue and green spaces: multi–dimensional equity evaluation of urban green–blue spaces distribution based on coupling theory in Hangzhou

The integrated development and equitable distribution of urban green–blue spaces (UGBS) are important for sustainable and socially inclusive cities. Despite extensive research on equity in green spaces, comprehensive assessments of equity in UGBS and the coordination relationship between blue and green spaces remain scarce. Based on coupling theory, a multi-level UGBS equity evaluation framework of “spatial equity-social equity” was established. The supply-demand matching, green–blue coordination, and social equity of UGBS distribution in Hangzhou were assessed by coupling coordination model, Gini coefficient, and spatial autocorrelation. Results show: (1) UGBS distribution in Hangzhou exhibits a significant supply-demand mismatch and blue–green incoordination, with both metrics being higher in the urban core than in suburban areas; (2) Disparities and inequalities in UGBS resource among different socio-economic groups are observed, with low-income populations face greater inequality than middle- and high-income populations. (3) Affluent groups are spatially concentrated in urban core areas with high UGBS supply and coordination levels, while low-income and certain middle-income groups are disadvantaged in accessing UGBS. (4) The inequality in green–blue coordination is more severe than that in supply level. Finally, three spatial patterns of UGBS among vulnerable groups were identified, and specific planning measures were proposed. This study constructed an equity evaluation framework for integrated UGBS, providing recommendations for planning policies guided by equity.