珠江河口磨刀门口外拦门沙近期演变分析

珠江河口磨刀门口外拦门沙的形成,受径流、潮流、沿岸流、波浪影响,且河口的地形条件及泥沙运动也是拦门沙的重要影响因素。根据近40 a来实测地形资料,对磨刀门口外中心拦门沙、西侧拦门沙、东西两汊深槽的演变进行了分析,并对拦门沙区域的冲淤变化进行了讨论。分析结果表明珠江河口磨刀门口外拦门沙区东、西汊不断向海延伸、拓宽,大洪水对东、西汊的发育起到显著促进作用;东汊走向则有一定摆动,东汊发育具有显著的季节性特征,受波浪改造作用明显;中心拦门沙内外坡以冲刷为主,滩顶淤积加高,南北径缩短;西侧交杯沙在波浪作用下呈新月形发育,交杯四沙向陆并岸的过程中,易受到洪水冲决作用,在并岸的浅滩中冲出深槽。研究结果可为河口规划、整治提供参考。

Recent Evolution of Mouth Sand Bar Outside Modaomen Estuary of Pearl River

The formation of mouth sand bar outside Modaomen Estuary of the Pearl River is subject to the influences of stream flow,tidal current,offshore current and wave.Besides,morphological condition and sediment transport are also key factors affecting the evolution of mouth sand bar.According to measured topographic data in the last four decades,this study is devoted to analyze the evolution of the central and western parts of mouth sand bar and its tidal channels.The morphological evolution in the mouth sand bar area is also investigated.Results indicated that 1 )promoted by big flood events,the tidal channels on both sides of mouth sand bar extended and broadened step-wisely;2)the eastern channel presented a certain swing trend,which was affected by explicit seasonal characteris-tic and wave effect;3)the inner and outer slopes of central mouth sand bar were eroded,while the crest was de-posited and heightened,with the north-south diameter shortened;4)the Jiaobei sand bar on the west side was cres-cent-shaped due to the wave effect,and was prone to be scoured with channel down cutting by flood.The research result provides reference for the planning and rectification of the estuary.