黄河三角洲潮滩剖面特征
CHARACTERISTICS OF TIDAL FLAT PROFILES IN THE YELLOW RIVER DELTA
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摘要: 利用验潮、潮滩水准测量、沉积物分析和遥感资料,分析了黄河三角洲不同岸段潮滩的特征。水准测量表明,侵蚀潮滩剖面形态为下凹,而淤积潮滩则上凸,由高潮线至低潮线,潮滩沉积物均变粗,这种变粗趋势在北部侵蚀岸段和河口侧缘明显,在河口南侧稳定海岸则不明显。潮滩沉积物含水量为12.2%~32.2%,平均为21%,海滩表层沉积物不排水剪切强度在0.1~0.35 kg/cm2之间。受局限岸滩的平面形态和剖面形态受到周围大坝地形影响,具有和砂质海滩类似的形态,显示波浪对该潮滩的作用强烈,根据剖面测量结果与遥感图像,发现河口北侧有一个小的冲积扇。Abstract: Data from tidal gauges, tidal flat profiles and surface sediments analysis were used to study 3 different types of Yellow River delta coast. Particle size analysis shows that, from the mean high water level to low water level, sediments on all the profiles become coarser. The trend is more pronounced in the profiles near the river mouth and erosional coast than that in stable coast. The content of water in sediments ranges between 12.2% and 32.2%, and the shear stress between 0.25 and 0.35 kg/cm2. By integrating remote sensing images and profiles data with GIS, we get much knowledge about sediment dynamics of the delta tidal flat. The tidal flat that is controlled by man-made dykes shows common characteristics of a beach in profile shape and in planform. Its profile is concave-up and the planform is a curved dry/wet line facing dominant wave direction, which indicates strong influences of wave actions. A small crevasse-splay formation is seen on the tidal flat in the north part of the river mouth, where sediments are coarser than that at the other part and show dark fan shade in the remote sensing image. It is found that the low water line from the remote sensing images does not correspond with the field data.