Analytical Model of Velocity Distribution and Penetration Characteristics in Water‐Level Fluctuation Zone With Vegetation

Abstract As a critical ecological transition zone between aquatic and terrestrial ecosystems, the water‐level fluctuation zone significantly influences flow structure through vegetation morphology. Conventional analytical velocity models inadequately address the variation in vegetation with water depth. In this study, we developed a hydrodynamic coupled model with vertically varying leaf vegetation widths and derived its analytical solutions. We have updated the dynamic invasion width formula in the context of studying vegetation‐flow interactions within water‐level fluctuation zones. This work quantitatively investigates flow interactions at the main channel‐floodplain interface, establishes a dynamic relationship between the resistance coefficient and vegetation geometric parameters, and proposes a modified Kármán coefficient expression incorporating free water layer corrections under submerged conditions. Experimental and numerical validation revealed the shear layer evolution mechanisms and turbulent kinetic energy redistribution patterns (vertical‐lateral) under semi‐vegetated conditions. This study overcomes the traditional assumption of vegetation homogeneity. The findings will provide a fundamental basis for research on dissolved oxygen variations and pollutant diffusion processes in the littoral zone under vegetation‐flow interactions. It also analyzes the vertical variations in vegetation morphology within water‐level fluctuation zones, and offering a high‐precision analytical tool for eco‐hydrological simulations under vertically graded vegetation configurations and associated hydrodynamic impacts in these zones.