River Functional Assessment: Model Development and Application in Yangtze Estuary, China

The Yangtze Estuary is confronting unprecedented challenges due to intensifying human activities and a rising incidence of extreme weather events, which collectively threaten its essential functions in flood control, water supply, ecological sustainability, and navigation. In this study, the functions of the Yangtze Estuary under evolving hydrological and sediment conditions are comprehensively investigated and evaluated based on long-term measurement and statistical data. Using the comprehensive indicator evaluation method (CIEM) and the analytic hierarchy process (AHP), a River Functional Assessment Model for the Yangtze Estuary (RFAM-YE) is developed. The model incorporates four sub-models: flood control, water supply, ecological protection, and navigation demand. The southern branch of the Yangtze Estuary is selected as a case study for evaluation. The results show that in recent years, the flood control capacity, waterway stability, and ecological conditions in the southern branch have improved. However, the ongoing overall erosion trend poses a threat to water supply security and the integrity of biological habitats. The assessment results are generally consistent with actual engineering conditions, demonstrating the validity and applicability of the proposed model. Finally, recommendations for the protection and restoration of the Yangtze Estuary are proposed based on the evaluation. This study provides both theoretical and practical references for the management and conservation of the Yangtze Estuary.