近期辽东湾西侧砂质海滩冲淤特征

PRESENT SCOURING AND SILTATION PATTERN OF THE SANDY BEACH IN EASTERN LIAODONG BAY

2013—2014年,在辽东湾六股河口两侧开展了海滩地形及海岸侵蚀的现场调查,于兴城至绥中沿海布设6处调查岸段及17条断面。结果表明,研究海滩地貌主要组成部分包括反射型高潮滩-滩坎-消散型低潮滩,其中低潮滩多发育有近岸沙坝和水下沙坝。绥中南江屯、皮家屯及兴城新立屯海滩侵蚀明显,多数海滩持续侵蚀,调查期内最大平均下蚀速率达53.2cm/a。分析发现,海滩地形及断面蚀淤量有较明显的季节或区域差异。海滩冬季近岸沙坝消失、水下沙坝离岸距离小于夏季。六股河口南侧夏季海滩断面侵蚀量增加、淤积量减少,而六股河口北侧相反。研究认为,岸线自然形态差异及其造成的沿岸输沙差异是导致不同岸段蚀淤差异的主要自然原因。海岸封闭性建筑物(尤其是突堤)影响了海滩局部断面蚀淤变化。海滩地貌及蚀淤的季节或区域变化的主要原因为沿岸波浪特征等因素的季节性和区域性差异。

During 2013—2014,field investigation was taken on the two sides of the Liugu River in the Eastern Liaodong Bay.6investigation sites and 17 profiles were selected between Xingcheng and Suizhong.Results show that the studied beaches are mainly composed of reflective high-tidal beach,scarp,dissipative low-tidal beach with nearshore sand bars and underwater sand bars.During the investigation times,obvious erosional records were found in Nanjiangtun,Pijiatun and Xinlitun,and continuous erosion occurred at most of the profiles.The largest erosion rate came up to 53.2cm/a according to our record.It is inferred that there exit seasonal or regional diversities in beach morphology variation and profile erosion/siltation rate.In winter,nearshore sandbars disappeared and the offshore distance of the underwater bars became shorter than that in summer.The erosion rate increased and accumulation rate decreased on the north of the Liugu River,and it is in opposite in the south.It is also found that the change of natural coastline shapes leads to the variation of longshore sediment transport.These variations are supposed to be the main natural cause of variation of erosional and siltation pattern.Local morphology variation is influenced by coast structures(especially jetties).Meanwhile,the diversity characteristics of waves led to seasonal or regional diversities in beach morphology variation and profile erosion/siltation rate.