Coupling mechanism of the eco-geological environment in debris flow prone area: A case study of the Bailong River basin.

Debris flow disasters can directly indicate the quality of an area's ecological and geological (eco-geological) environment. Coordinating the coupling mechanism between these environments is crucial for reducing debris flow incidents and promoting sustainable socio-economic development. Nevertheless, comprehensive research on the coupling coordination mechanisms of the eco-geological environment in high-prone areas of debris flow has yet to be reported. This study focuses on the Bailong River Basin (BRB) and proposes two main hypotheses: (1) There is a coupled relationship with mutual influences among the eco-geological environmental systems; (2) The eco- geological environment affects debris flows, with geo-environmental factors having the most significant impact. To validate first hypotheses, this study developed an assessment index system for the eco-geological environment, encompassing geological environment, ecological environment, and human activities. We applied the projection pursuit model and the coupling coordination degree (CCD) model to calculate indicator weights and analyze the coupling coordination mechanisms. The results indicate that the three subsystems interact with each other. To validate second hypotheses, the self-organizing maps (SOM) method categorized the eco-geological subsystems. Building on this foundation, we analyzed the impact of the eco-geological environment on debris flow using variance decomposition analysis (VDA) and redundancy analysis (RDA) methods. The results indicate that eco-geological environment account for 87.8 % of the variation in debris flow frequency, with geological factors having the most significant impact. Notably, the area with the highest frequency of debris flow (four times per year) is located near the urban center of Wudu District, where the human environment subsystem is overwhelmingly dominant and the quality of the ecological and geological systems is comparatively low. Consequently, we analyzed the reasons behind the differences in clustering areas and proposed specific recommendations, including enhancing geological disaster prevention and monitoring potential hazardous areas. Future research should focus on enhancing data accuracy and exploring more effective methods for integrating ecological and geological environments with debris flow disaster management for functional zoning. In conclusion, this study provides scientific support for strategies to prevent or mitigate debris flow disasters and protect the BRB ecosystem by validating the above two hypotheses.