Advances in understanding the geomorphological processes of the Yellow River Delta under changing water and sediment conditions

Understanding the morphodynamic evolution of the Yellow River Delta is a key scientific issue for elucidating deltaic sedimentary processes and sustaining ecological stability, with significant implications for regional flood control and wetland conservation. Compared with the latter half of the 20th century, the mean annual river discharge entering the Yellow Sea has decreased by approximately 40%, while the sediment load has declined by more than 80%, indicating a marked reduction in fluvial sediment supply and an increasing dominance of marine dynamics in sediment–erosion processes. This paper provides a comprehensive review of research progress since the 1980s on the major morphodynamic processes of the delta under changing water and sediment regimes, including mouth-bar and channel evolution, tidal-flat and creek adjustments, shoreline dynamics, and vegetation succession. Mouth-bar development and channel avulsion exhibit positive feedbacks that drive lobe-building cycles; tidal-flat systems are characterized by frequent bank collapses and progressive creek widening; shoreline evolution shows coexistence of accretion at the active delta lobe and erosion at abandoned lobes, governed by a critical sediment-supply threshold; and vegetation communities, particularly following the invasion of Spartina alterniflora, have undergone significant homogenization and fragmentation. Future studies should aim to deepen understanding of sediment transport and ecological feedbacks under freeze–thaw processes, quantify multi-scale thresholds of erosion–deposition balance and their constraints on system stability, and elucidate the nonlinear responses arising from the combined impacts of human regulation and extreme climatic events, thereby providing scientific guidance for predicting delta evolution and promoting ecological restoration in the Yellow River Delta.