不同水文条件下通州沙河段沿程分流分沙特征

通州沙河段受径流与潮流双重作用，江中沙洲、暗滩交替分布，江心洲滩冲淤演变剧烈，航道边界条件不稳定。通过三维水沙数学模型对天然河段洪、枯季水流条件的沿程分流、分沙比及滩槽过渡断面的水沙交换特征进行分析。结果表明，通州沙东水道是主要的涨落潮通道，落潮时上游分流比约90%，往下游分流比逐渐减小至75%左右；涨潮时东水道下游分流比约70%，上游段受西水道漫滩流影响东水道分流比增至85%~90%。洪、枯季落潮期间通州沙东水道的分沙比较对应的分流比有所增加，洪季涨潮期间通州沙东水道的分沙比较对应的分流比有所减小，枯季时变化相对不明显。通州沙下段左缘水流交换和悬沙交换的格局相同，均以槽向滩为主，狼山沙右缘水沙交换通量较小。

Water-sediment diversion ratio along Tongzhousha shoal reach under different hydrological conditions

The river regime of the Tongzhousha shoal is controlled by both the actions of the river runoff and tidal current. There are many shoals and ditches existing in the river, and a rapid evolution by erosion and deposition makes the channel boundary conditions become unstable. Using a three-dimension mathematical model, the analyses of the diversion ratio of flow and sediment in flood and dry seasons and the water-sediment exchange characteristics along the shoal-ditch section were carried out. The analysis results indicate that the east waterway is the main channel. During the ebb tide, the upstream diversion ratio is about 90%, and the diversion ratio decreases by 75% at the downstream. The diversion ratio is about 70% in the downstream, and increases by 85%~ 90% during the flood tide as a result of the overflow from the west waterway. During the ebb tide, the sediment diversion ratio, comparing corresponding diversion ratio, increases in both flood and dry seasons. In contrast, the diversion ratio of sediment during the flood tide in the flood season decreases, comparing corresponding diversion ratio, while no significant changes are found during the dry season. The same water-sediment exchange characteristics are found along the left side at the lower Tongzhousha shoal, and the primary transport direction is from the ditch to the shoal, and there is a smaller water-sediment exchange flux at the right side of the Langshansha shoal.