薛家岛岬湾型海岸侵蚀演化的定量性研究

在4a连续观测的基础上,确定薛家岛周边大部分是抗蚀强度大的基岩岬湾海蚀岸,海蚀崖蚀退和海蚀平台蚀低的平均速率分别为10-2和10-4m/a量级;弓形海湾湾顶有薄层现代海滩砂砾,石雀湾和银沙滩崖前和后滨有大量海滩相大砾石(粒度为20～30cm).外侧海岸直濒开阔海,水下岸坡为深陡型,气象水文等外营力因素作用强度较大,显示中—高能海岸环境地质地貌特征.薛家岛外海海岸冲积物供给源贫乏,小于2×104m3/a.沿岸冲积物流流向北东至南西,采用目前国际较通用的波浪辐射应力模式方法计算其容量达13×104m3/a,这种源-运量的不平衡是造成基岩海蚀岸的机制.

Quantitative study on the evolution of the Xuejiadao headland-bay coast erosion

Quantitative study on the Xuejiadao coast evolution based on 4 a continuous field survey shows that most margin of the Xuejiadao area is the bedrock headland-bay erosive coast whose anti-eroding strength is great.The average velocity of the back-eroding and down-eroding is at the level of 10^-2 and 10^-4 m/a,respectively.There is modern beach grit lamella on the tip of the bow bay,and a great deal of big gravels of beach-faces in front of the cliff and on the backshore of Shique Bay and Silver Beach (the granularity of them can reach 20~30 cm).Outside coast is facing to the open sea,and the underwater bank slope is steep and deep,the intensity of exogenetic force factors such as meteorology and hydrology is relatively great.All these features display the geological and geomorphological characteristics of middle-high energy coast.The source of alimentation of the coastal wash in the open sea off Xuejiadao is poor,which is less than 2×10⁴ m³/a.The direction of littoral wash flow is from northeast to southwest,and the capability can reach 13×10⁴ m³/a.The unbalancedness between sediment source and carrying capacity is the mechanism of the formation of the bedrock erosive coast.