THE EROSION OF GRAVEL BEACHES IN NORTHERN COAST OF ZHIFU ISLAND

The tideland gravel in the east of Popokou where in the northern coast of Zhifu Island is studied in this paper.The character of gravel beaches and it's changes in space were obtained by surveying and analysis in May,2004,and in May,2007.The surveys and statistic indicate that the gravel beaches in May,2005,is natural,and the constitute is integrated.There are two strip ridges in the gravel beaches.But the gravel beaches are abnormal,and not integrated in May,2007.There is some bedrock comes out on the beaches.The isoline of 38mm in grain size was gained by the statistic character of gravel beaches,the result showed that the isoline moved towards the sea with time.The change of average diameter in space is due to motivity of abnormal ocean that makes the gravel to adjust rapidly.It relates to the huge storm tide in March,2007.