黄河口快速沉积及其动力过程

现场观测资料和卫星遥感校准图像计算表明 ,185 5年以来 ,黄河三角洲新淤陆地 36 99km2 ,生长速率为 2 6 8km2 /a ,黄河输入三角洲 1× 10 8t泥沙形成 3 14 4km2 的陆地。进入河口区的泥沙约 88 4 %堆积在水下 8km宽的三角洲前缘。研究表明 ,这一堆积比例是河口切变锋、异重流和潮流场相互作用的结果 ,异重流在黄河汛期一直存在 ,大约搬运黄河来沙的 6 0 %沉积在三角洲前缘 ;一个潮周期内 ,切变锋出现两次 ,它能够捕获异轻羽状流中的悬浮泥沙堆积 ,也能够限制异重流的远距离扩散。切变锋消失后 ,少量悬浮泥沙才能远距离扩散 ,随潮流离开三角洲水下斜坡。

RAPID DEPOSITION AND DYNAMIC PROCESSES IN THE MODERN YELLOW RIVER MOUTH

Based on the recent computation, the new land of 3 699 km2 with a mean accretion rate of 26.8 km2/a has been built on the modern Yellow River delta since 1855AD. 1×108 t silt from the river can build 3.144 km2 of new land. More than 88.4% of the suspended silt into the river mouth area is deposited on the delta front slope of average 8 km in width. Such high deposition proportion on the river mouth area is infrequent in the worldwide rivers. This study has proved that the proportion results from combination and interaction of the shear front, hyperpycnal flow and tidal current off the Yellow River mouth. The hyperpycnal flow has always occurred as ebb in the flooding season. It transports about 60% of the suspended silt of the river to accumulate on the delta front. The shear front occurs twice during a tidal cycle. It can capture the suspended silt from hypopycnal plume to deposit on the delta front and limit the hyperpycnal flow to disperse farther. When the shear front disappears, a little part of the suspended silt in the hypopycnal plume is advected off the delta slope with the tidal current.