Spatiotemporal evolution and driving factors of urban form resilience under flood hazard disturbance: A case study of 137 cities in the southeast monsoon influence zone of China.

Over the past two decades, global climate change and rapid urbanization have led to increasingly frequent and severe urban flood disasters in the southeastern monsoon region of China. Urban form has emerged as a crucial means of mitigating flood risks. However, the capacity of different urban form structures to cope with uncertain flood disturbances remains unclear. In response, this study takes 137 cities in the southeast monsoon region of China as an example to construct an Urban Form Resilience Evaluation Framework under Flood Disturbance (FD-UFREF) that covers the three stages of disaster-incubating space, disaster-bearing space, and disaster-response space, as well as the cross combination of ecological, physical, spatial, and functional urban form elements. Based on AHP and improved spatiotemporal entropy weight method, indicator weights are determined to evaluate FD-UFR of cities from 2000 to 2020. Spatiotemporal evolution patterns and driving factors of FD-UFR are explored through spatial analysis and geographic detectors. Key findings include: (1) Urban form resilience shows an overall upward trend, with an average increase of 10.89 %, but significant spatial disparities persist, following a spatial pattern of "high in the west, low in the east" and an "inverted U-shape" from north to south; (2) Disaster-incubating spaces have consistently exhibited higher resilience, with the most substantial improvement observed in disaster-response spaces. However, disaster-bearing spaces remain structurally weak, and some cities show an unbalanced resilience structure of "weak defense, strengthened response"; (3) FD-UFR demonstrates strong positive spatial clustering, with high-value clusters concentrated in the southwest and expanding low-value zones forming vulnerability belts along the eastern coast; (4) Urban centrality, impervious surface ratio, and terrain undulation are the dominant drivers of FD-UFR spatial heterogeneity. Additionally, the Urban Functional Resilience Index (REP)-constructed using extreme precipitation events and nighttime light data-was introduced for cross-validation of the FD-UFREF. The high spatial and statistical consistency between FD-UFR and REP (R = 0.661) confirms the robustness and applicability of the proposed framework. The findings provide theoretical and practical support for improving flood resilience planning in southeastern monsoon-affected urban regions in China.