揚子江汽水河道の脈動的土砂移動とその季節特性について

抄録

The flow field in the Yangtze estuarine channel is highly pulsatile throughout the year, because of its mild channel slope and large tidal amplitude. This paper compares the different tendency of topography change in flood season and dry season by using numerical simulation. The shallow water equations on the base of unstructured triangular mesh system are applied to calculate the flow field. The Laursen’s formula on bed sediment load is used to evaluate the topography change. The calculations result shows highly pulsatile sediment transport in thalweg and remarkable cross-sectional flow above the underwater shoals in both seasons. In dry season, due to the stronger landward transport, sandspits develops at the edge of underwater shoals. This small scale topography feature further develops in the next flood season and changes the flow field entirely. Considering the large sediment transport rate, the topography outline is formed in flood season. However, the small scale sandspit might be a key point to the topography change in the Yangtze Estuarine channel.