Delta-scale mapping of coastal erosion vulnerability at the modern Yellow River Delta and implications for geomorphic sustainability

River deltas are highly vulnerable coastal areas, particularly susceptible to human interference and environmental changes. Due to reduced sediment supply and strong coastal dynamics, deltaic coasts are struggling to maintain shoreline progradation, necessitating urgent needs for integrated and data-enriched vulnerability assessments to address erosion risks. However, previous studies have often been constrained by observational datasets and lacked a systematic analysis of erosion vulnerability in deltaic coasts during varying periods under combined human activities and climatic changes. The modern Yellow River Delta (YRD) serves as a typical river-dominated delta system, currently undergoing geomorphic transition and facing erosion risks due to changing environmental conditions. This study integrates methods of numerical modeling, Analytic Hierarchy Process (AHP), and Coastal Vulnerability Index (CVI) to develop a comprehensive framework for assessing coastal erosion vulnerability. We then apply this framework to evaluate the erosion vulnerability of different coastal segments of the YRD, using multi-year hydro-geomorphic and human-interfered indicators. The results reveal that the overall erosion vulnerability of the YRD has decreased during 1992–2015, characterized by pronounced spatial and temporal disparities. The abandoned northern YRD exhibits high erosion vulnerability, primarily due to the absence of fluvial sediment supply, strong coastal currents, and the additional impact of wave climate. In contrast, the artificially protected coasts and western Laizhou Bay show relatively lower vulnerability marked by coastal protection measures and weak hydrodynamic influences. The segment of Qingshuigou delta lobe shows high vulnerability in sediment-starved areas, attributable to both engineered diversions and natural channel migration. Future management strategies should integrate coastal protection measures with wetland restoration efforts, as well as optimize riverine water and sediment regulation within the river basin and deltaic channels to enhance riverine sediment delivery to severe erosion zones.