Abstract: This study investigates the characteristics of the ebb water and sediment diversion ratios during wet season in the North Passage, Changjiang Estuary and the reasons for the differences within neap-spring tidal cycles based on field measurements. The results of the measurements indicate that the averaged ebb flow diversion ratios of the North Passage in spring and neap tide are 41.9% and 43.1%, respectively, while the averaged ebb sediment diversion ratios of the North Passage in spring and neap tide are 35.1% and 39%,the averaged ebb sediment diversion ratios of the North Passage in spring can approximate representatively ebb sediment diversion status. The ebb sediment diversion ratio of the North Passage is dependent on the ratios of mean flow velocity, suspended sediment concentration and section areas of the North and South Passage. And these parameters show minor changes within neap-spring tidal cycles. Therefore, it can be concluded that the differences of ebb flow and sediment diversions of the North Passage within neap-spring tidal cycles are limited.

Key words: Changjiang Estuary, wet season, neap-spring tide, ebb sediment diversion ratio