MORPHODYNAMIC SYSTEM AND THE EVOLUTION OF LAOLONGGOU TIDAL INLET
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摘要: 老龙沟为典型沙坝-泻湖型潮汐汊道,潮汐汊道地貌结构完整。老龙沟口门处潮流动力最强,发育-20 m的深槽,口门内涨潮流三角洲上发育完整的多级水道体系。口门外落潮三角洲止于-11 m水深处,以突起的末端坝为地形标志,落潮主水道偏于落潮三角洲东侧发育,落潮三角洲西侧发育宽缓冲流平台。落潮主水道以落潮流为优势,冲流平台上潮流动力最弱,沉积物以粉砂质黏土为主。分割沙坝和末端坝上以砂质沉积为主,显示了波浪的二次分选作用。1945-2006年的地形对比显示波浪和潮流对老龙沟地貌演化的混合控制作用,偏东向波浪引起滨外沙坝和分割沙坝的迁移迫使落潮喷射流方向改变,引起了落潮水道的摆动,破波带内自东向西的沿岸泥沙流自老龙沟上游进入通道,部分堆积于口门内泻湖的潮间带,绝大部分泥沙堆积于老龙沟落潮三角洲。Abstract: Laolonggou is a typical tidal inlet as a part of the barrier-lagoon system of the north Bohai bay. The threshold of the inlet is 2.1 km wide and over 20m deep, and the maximum flood current or ebb current through the threshold may be over 1 m/s. A dendritic tidal drainage system is well developed on the flood delta with little sediment accumulation. According to the morphology of terminal shoal, the edge of the ebb tidal delta is located around -11 m of water depth. A main ebb tidal passage is developed on the east side of ebb tidal delta, in which ebb jet dominates. A swash platform with gentle slope is on the west side of the delta, on which the tidal dynamics is the weakest and the sediment the finest. On the shoal of terminal lobe and segmented sand bar, because of secondary sorting by breaking wave, silty sand and sand with shelly fraction deposited. The geomorphological evolution during 1945-2006 shows that both the tide and incident wave control the evolution of the morphological system of the Laolonggou tidal inlet. The main ebb passage swung westward due to the change of ebb jet under the influence of the movement of segmented sand bar and offshore barrier islands. The migration of the bar and islands was driven by the east and south incident wave. Most of sediment trapped at the tidal inlet is supplied by the longshore sand drift. Most of the sediment deposited on the ebb tidal delta, except part deposited on the intertidal flat around the Laolonggou lagoon.
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Key words:
- tidal inlet /
- flood tidal delta /
- ebb tidal delta /
- mixed energy
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