Simulation experiment on morphological evolution characteristics of tail river channel

The tail river channel serves as a critical zone for the interaction between rivers and oceans, holding significant ecological and environmental implications. This study employs a physical experimental approach to simulate the evolution processes of common trumpet-shaped and meander-shaped (left-bending and right-bending at the estuary) tail river channels. The research investigates the morphological evolution patterns under varying water and sediment conditions. Evaluation of different river types′ stability is based on coefficient of fluvial facies and relative roughness. The experiments reveal that the planar morphology of the river undergoes stages of "stability-micro-change-strong change." The average elevation and slope of the riverbed increase over time, with the most significant changes occurring in the upstream and estuary sections and the least in the midstream. Sediment addition results in upstream riverbank erosion and riverbed sedimentation. Following cessation, downstream and estuary sections experience more pronounced riverbank erosion than riverbed erosion, leading to estuarine bifurcation, oscillation, and shifting. The unstable areas in planar morphology are the downstream section for meander-shaped channels and the estuary section for trumpet-shaped channels, with significant differences in river phase coefficients. For cross-sectional morphology, the downstream section is unstable for left-bending meander-shaped channels (with a more than 3-fold difference in relative roughness), the upstream section for right-bending meander-shaped channels (more than a 2.03-fold difference in relative roughness), and the downstream section for trumpet-shaped channels (more than a 4.09-fold difference in relative roughness).