Dynamic geomorphological environment of large tidal channels in the South Yellow Sea and its response to human activities: a case study of Xiaomiaohong tidal channel

Due to the lack of a fixed boundary, the stability of tidal channels in radial sand ridges is more sensitive to the impact of human activities. In this study, based on high-resolution underwater topography data of the Xiaomiaohong tidal channel in the southern part of the radial sand ridges collected over the past 20 years, the morphodynamic responses to the cumulative impact of human activities are investigated and simulated by numerical modeling. Results show that the section discharges at the tail, middle, and head parts of the Xiaomiaohong tidal channel induced by reclamation, which has reached 126.09 km² in the past 20 years, are down 14.2%, 15.79%, and 9.13%, respectively; the average current velocities were also decreased by 20—30 cm/s, 10—20 cm/s, and 5—10 cm/s, respectively. The -5 m isobath on the southern side of the Xiaomiao channel has essentially remained stable with few changes; while the -10 m isobath is expanding westward and southward. Although the reclamation projects have resulted in a decrease of tidal capacity and hydrodynamics, the erosion and deposition they cause are restricted to the areas around the projects because of their high elevation. Overall, reclamation has little effect on the stability, southward moving, and the erosion trends of the Xiaomiaohong tidal channel.