Suspended Sediment Transport Characteristics in Offshore Area of Yangtze Estuary
|School||East China Normal University|
|Keywords||Yangtze Delta Chongming Dongtan Suspended sediment concentration Single - wide sediment load I flow|
Chongming Dongtan inshore waters is one of the most sensitive areas in the Yangtze Delta area land-ocean interaction. Yangtze River sand to reduce background the four marine survey of the region in 2009-2010, to study their spatial and temporal distribution of suspended sediment concentration and water and sediment transportation characteristics, and preliminary summary of its own rules, to analyze the formation of reasons for its impact on the evolution of the surrounding sedimentary environment. The study showed that: (1) the inshore waters of Chongming Dongtan plane distribution of suspended sediment concentration as low in the west high in the east, the main factors for the flow rate and the terrain. (2) the vertical distribution of the overall trend to gradually increase the ground surface to the bottom surface suspended sediment concentration is 1.9-6.2 times that of the bottom of the end of the flood season, the difference is greater than the concentration of suspended sediment surface Dry Seasons, at the same time, the tide than neap. (3) 2301 site suspended sediment concentration peaks occurred mainly in the drop-anxious, the drop turn up, up anxious these three periods, and often lag 1-2 h, appears mainly due to rise anxious drop velocity anxious moments, and high background values ??of suspended sediment concentration in off the turn up moment, and brine density flow caused by the convergence of upwelling, the three peak often at the same time there are two to form a bimodal phenomenon. (4) 2301 sites tide of suspended sediment concentration suspended sediment concentration higher than the neap tide suspended sediment concentration small influx of 1.7-3.6 times, mainly affected by the tide of greater velocity. (5) 2301 Site DRY SEASON suspended sediment concentration higher than the flood season in 2010 DRY SEASON tide of suspended sediment concentration 2.1 times that of the 2009 flood season the tide of the major influencing factors for the storms and runoff turbidity maximum zone dilution. (6) historical measurements, the 2301 site in the 2009 flood season suspended sediment concentration lower than 1982, the 2009 flood season neap tide suspended sediment concentration of only 40% in 1982, mainly due to basin sediment reduction; 2010 Dry Seasons average suspended sediment concentration slightly higher than in 1982, played a more important role in the local terrain, hydrodynamic conditions and human activities. (7) layers of the single-wide sediment transport, water and residual current direction of the various sites along the vertical changes consistent, three close contact. I stream flows to some extent represents net suspended sediment transport direction, but will not entirely due to the flow rate and the concentration of suspended sediment into a positive correlation between complex estuary in dynamic conditions, I flow direction and unit width sediment transport direction The inconsistencies. (8) the Peikang by Chongming Dongtan Beigang Beisha Wang ditch re-suspended sediment transport of sediment and offshore extension is the Chongming Dongtan sediment in an important source, the basin sediment significantly reduced in recent years, Chongming Dongtan -4 m to the sea side to deep shore beaches have eroded from siltation to these changes will affect the the Chongming Dongtan sediment supply, so Chongming Dongtan retrogradation phenomena may occur in the future.