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.