利用现场水文、泥沙以及水下地形观测资料，分析了近期九段沙的冲淤演变过程、机理及其对北槽航道回淤的影响。结果表明，近10年来九段沙总体呈现“长高不长大”的变化特点，即0m以上高滩淤涨明显，而2m和5m中低滩面变化不大。九段沙的淤高使得南导堤的挡沙功能减弱，一定的风浪条件下九段沙滩面相对较高浓度的含沙水体涨潮越堤进入北槽中段，增加了近期北槽航道回淤的泥沙来源。

 On the basis of the field measurement data of hydrology, sediment and underwater topography, the evolutional process and mechanism of Jiuduan Shoal (JDS) in recent 10 years and its effect on navigation channel sedimentation of the North Passage (NP) are analyzed. The results are showed that JDS presents overall a feature of growing taller not bigger, i.e. the high shoal of elevation above 0 m is raising obviously, but the low shoal of elevation above 2m and 5m is stable. The higher beach of JDS is weakening its function of blocking sediment of South Training Dikes in the 2nd phase Deepwater Channel Project, and the rising tidal current with relatively higher sediment concentration on the beach face of JDS across South Training Dikes discharges into the middle reach of NP under certain condition of wind and waves, which would increase sediment sources of navigation channel sedimentation of NP in recent years.