Effect of evacuating sand on Jiaojiang River estuary

Niutoujing on the mouth sand bar separates the Jiaojiang River estuary into two parts.The inner region is Jiaojiang River,Lingjiang River and Yongning River and the outer region is Jiaojiang River estuary.In ordinary circumstances,the sediment is transported back and forth between the outer and inner mouth bars with the variation of high and low runoff in Jiaojiang River basin.The phenomenon of scouring during floods and silting during tides emerges in the bed inside the mouth bar,but it is opposite for the bed outside the mouth bar,and in general the bed is stable under the natural condition.After 1990,an exceptional change in Jiaojiang River estuary bed was taken place and the bed was continuously dropped.The drop scope inside the mouth bar was obviously larger than that outside the mouth bar.The analyses show that the short-term exceptional variation is caused mainly by evacuating sand in Jiaojiang River and Lingjiang River on the mouth bar.And the sectional variation scope of Jiaojiang River estuary has been verified by estuarine hydraulic geometry.