Research on the coupling and coordination of urbanization and flood disasters based on an improved coupling coordination model: A case study from the pearl river delta in China

Against the dual backdrop of global climate change and rapid urbanization, urban flood disasters have become increasingly frequent and destructive, posing severe threats to urban safety and sustainable development. This study examines the Pearl River Delta region (2005-2023) as a case study, integrating urbanization and flood disasters into a unified framework to elucidate their interactive mechanisms. The research employs RAGA-PPM to quantify urbanization levels, utilizes a GIS-based spatial multi-indicator model to assess flood disaster risks, and constructs an improved Coupling Coordination Degree (CCD) model alongside a coordination influence model to analyze their dynamic interrelationships. Key findings reveal: (1) During the study period, urbanization levels in the Pearl River Delta showed significant improvement, while flood disaster risks exhibited fluctuating upward trends; (2) The CCD between urbanization and flood disasters displayed a phased transition from "barely coordination" to "mild coordination" and back to "barely coordination," with a spatially concentric pattern increasing outward from the Pearl River estuary cities (Shenzhen, Zhuhai, Dongguan, Foshan, Zhongshan, and Guangzhou) to the peripheral areas (Jiangmen, Huizhou, and Zhaoqing); (3) Regarding flood disaster subsystem's influences on CCD, hazard factors, disaster-prone environments, and disaster-bearing entities in "innerring" cities primarily exerted negative hindering effects, whereas disaster-prone environments and disasterbearing entities in "outer-ring" cities generally demonstrated positive promoting effects, with the intensity of these effects progressively strengthening over time. The study recommends transcending traditional economic growth-oriented urbanization paradigms in favor of ecologically prioritized, risk-preventive sustainable development pathways, optimizing human-land relationships through spatially differentiated governance approaches.