Effects on sediments following water-sediment regulations in the Lixia River watershed, China

To decrease deposition of sediment and improve navigation capacity in the Lixia River watershed, China, a water transfer process was initiated. From 2006 to 2007, water was transferred from the Yangtze River to the Lixia River watershed to divert sediment out of coastal channels. Different operational strategies were employed, including varying the transfer capacity and timing of the water and altering the management and regulation of the water resources project (i.e., the volume of water transferred and the height of the water gate). The types of operational models that were applied to determine changes in the water quantity included the following: water level, cross-section, scouring, and silting. Based on the cross-sectional area, the volumes of silting and scouring in the lower reaches of four coastal channels were estimated. It is generally known that river discharge and tidal mixing affect sediment scouring considerably. However, the most pronounced scouring effects were found to occur upon suddenly opening the sluice gate with the water head upstream of the gate. Thus, sediment scouring should be considered preferentially for the downstream channel of the Sheyang River during a spring tide, but should be considered preferentially for the Doulong and Xinyang ports during a neap tide. The results of this study provide useful information for local governments and decision-makers to better regulate and control flow and sediment transport relationships in order to restore and maintain flood channels; these results will assist in managing water transfer projects.