山东荣成天鹅湖沙坝水下岸坡地貌冲淤演变分析

Erosion-deposition analysis of underwater slope on lagoon and sand barriers in the Swan Lake,Rongcheng,Shandong province

山东荣成天鹅湖是一个典型的潟湖-沙坝系统。自20世纪80年代以来,因受人类活动的影响,天鹅湖环境系统发生了改变,沙坝侵蚀后退严重。研究水下岸坡的冲淤对于认识潟湖-沙坝系统演变,以及保护天鹅湖环境具有重要意义。本文以天鹅湖东侧沙坝水下岸坡为研究区域,基于1960年至2014年的海图资料,采用地理信息技术,获得了天鹅湖东侧近岸海域多年水深数据,进而分析了1960年以来天鹅湖东侧沙坝地区的等深线变化、冲淤变化以及固定剖面的地形变化。结果表明:1960-1980年等深线整体向海推移,而1980-2014年等深线向海推移趋势变缓,1960-2014年潮汐通道口门处0m等深线向岸退缩了126.70m。天鹅湖水下岸坡在1960-1980年整体处于淤积的状态,年淤积率为3.60cm·a;1980-2014年侵蚀面积显著增大,且呈现冲淤相间分布的特点,年淤积率为0.79cm·a。天鹅湖沙坝水下岸坡呈现上陡下缓的形态,且潮汐通道口门北侧比南侧更易受到侵蚀。人类活动改变了天鹅湖的环境状态,导致了天鹅湖水下岸坡的局部侵蚀后退。

The Swan Lake in Rongcheng of Shandong province is a typical lagoon-barriers system.Since 1980s,under the influence of human activities,the environmental system of the Swan Lake has changed with strong erosion of the sand dam.Studying the erosion and deposition of underwater bank slopes is of great significance for understanding the evolution of lagoon-sand dam system and protecting the environment of Swan Lake.This paper focus on the underwater bank slope of the sand dam at the east side of the Swan Lake.Based on the combination of chart data from 1960 to 2014 and geographic information technology,we have obtained multi-year water depth of the coastal waters on the east side of the Swan Lake since 1960,and analyzed the contour changes,scouring and silting changes and topographic changes of the set profile in the sand dam area on the east side of Swan Lake.The results show that the overall depth contours moved towards the sea from 1960 to 1980,while the tendency of contours moving towards the sea from 1980 to 2014 slowed down,the 0 m depth contour at the entrance of the tidal channel retreated 126.70 m to the shore from 1960 to 2014.The underwater bank slope of the Swan Lake was at a state of siltation from 1960 to 1980,the annual siltation rate is 3.60 cm·a^(–1).The erosion area increased significantly from 1980 to 2014,and the erosion and siltation phases were distributed,the annual siltation rate is 0.79 cm·a^(–1).The underwater bank slope of the Swan Lake sand dam is steep and gentle,and the north side of the tidal channel entrance is more likely to be eroded than the south side.Human activities have changed the environmental state of the Swan Lake,leading to partial erosion and retreat of the underwater bank slope of the Swan Lake.