黄河口拦门沙与盐水楔特征及其演变

BASIC CHARACTERISTICS AND EVOLUTION OF THE MOUTH BAR AND THE SALINE WEDGE OF THE YELLOW RIVER ESTUARY

黄河口存在一个成型堆积体，称拦门沙。多次实测结果，其长度约3～7km，宽度与河宽相同，横亘于黄河尾间与海水相连接处。随着河口延伸，拦门沙也向海推移，淤积最多的部位是前缘急坡区。在拦门沙以上河段，由径流挟带的泥沙和涨潮流引起的悬移泥沙，形成一高含沙区，此高含沙区在洪水时向下移动，在枯水时向上移动，泥沙在这3～7km范围内大量落淤。由于拦门沙的阻拦，水流在拦门沙处受阻而在其上游不断出汉。黄河口的盐水楔在径流较大时，属缓混合型；枯水季节是强混合型。盐水楔上下游运动的范围与拦门沙的长度基本上吻合。

At the Yellow River estuary, there exists a shaping accumulation of sealment customarily called the mouth bar. The measured data of many times indicate that the mouth bar is about 3-7km in length and has the same width as the rived,spanning the junction of the Yellow River sink and the sea. With the extension of the river mouth, the bar will shift seawacds. The position with the greatest amount of deposition lies at the front steep slope zone. In the river reach upstream of the bar, the sediment carred by runoff and the suspended load caused by tidal flood current have formed a hyper-concentration zone, which shifts downstream during flood period and upstream during dry perion and where, in the range of 3-7km,a large amount of sediment is deposited. Due to the blocking effect of the bar on the water, the flow is obstructed here and branches out constantly in the upstream.The saline wedge of the estuary assumes a gentle mixed type in larger runoff period and becomes of a strong mixed type in dry period. The shifting range ofthe saline wedge basically tallies with the length of the mouth bar.