Two-dimensional Numerical Modelling of Channel Adjustments in an Alluvial River with the Effect of Various Regulation Engineering

Abstract: In an alluvial river, various river regulation engineering (e.g. bed- and bank-protection works) is usually constructed along the reach in order to keep the stability of channel regime and the safety of flood control, which significantly affects the process of channel evolution. Therefore, a two-dimensional (2D) morpordynamic model has been develope, with the influence being considered of bed- and bank-protection engineering on channel evolution. First, the study domain was divided into a set of cells, and the nodes are labeled by different point codes to discriminate the zones of floodplain and main-channel with and without regulation engineering. In the improved module of bed level updating, bed deposition is permitted to occur at each node of the computational domain, and however, bed scour is not permitted to occur in local regions with the protection of various river regulation engineering. The 31-km-long Shishou reach in the Middle Yangtze River was selected as the study region. Large-scale bank-revetment works were constructed along this reach, with the whole length of protected banklines on both sides up to 46.8 km. In addition, bed-protection works was also implemented in local regions of Tianxingzhou, Nandiguai, etc. Channel adjustments of this reach in 2016 were simulated using the improved 2D model with and without the consideration of regulation works. Simulated results show that the calculated channel scour volume was significantly under-estimated when regulation engineering was not considered in the model, and the value considering the effect of these engineering was in close agreement with the measurements. Furthermore, it is investigated of the influence of regulation works on the processes of flow and sediment transport, as well as channel deformation in the study reach, such as the lateral distributions of flow velocity and sediment concentration, and the variation in cross-sectional geometry.

Keyword：River regulation engineering; two-dimensional morpordynamic model; channel adjustments, Shihou reach, Middle Yangtze River