中文摘要：

长江口南港是上海外高桥新港区所在岸段,其冲淤变化对该港区水深的维护具有重要影响。本文利用ArcGIS对2000-2008年长江口南港海图资料进行数字化,建立不同时期此河槽的数字高程模型,定量计算南港河槽尤其是主槽的冲淤变化,分析其演变规律。结果表明：（1）2000-2004年南港河槽整体上冲刷21.9×10^6m^3（平均冲刷速率为3.5cm/a）;（2）2004-2008年南港河槽整体上转为淤积,河床共淤积26.0×10^6m^3（平均淤积速率为4.1cm/a）;（3）2004-2008年外高桥新港区净淤积73cm,其中2006年7月-2007年7月1年淤积57cm。结论包括：（1）南港复式河槽中间沙脊的大量采砂导致的过水断面调整可能是近期沙脊两侧深槽出现淤浅趋势的重要原因;（2）2006年7月-2007年7月南港主槽（包括外高桥新港区）的强烈淤积可能还与该水文年长江径流量特低有关。（3）南港作为长江入海水沙的过境通道,其冲淤变化与河流来沙量变化的关系不大,而流域极端气候事件导致的径流量变异、河口人类活动以及河槽的自适应调整可能是该河槽年际冲淤变化的更重要诱因。

英文摘要：

The accretion/erosion of the South Channel of the Yangtze River has significant influence to maintain the new harbor of Waigaoqiao. The article use the ArcGIS to digitize the topographic maps of the South Channel from 2000 to 2008 and establishs the DEM model of the South Channel between different periods to calculate the accretion /erosion rates. The results show that： （1） from 2000 to 2004, the amount of erosion in south channel was 21.9×10^6 m^3（the erosion rate was 3.5 cm/a）; （2） during 2004-2008 it turned to accretion ,the amount was 26.0×10^6 m^3（the accretion rate was 4.1 cm/a）; （3） from 2000 to 2004, the average accretion in the new harbor of Waigaoqiao was 73 cm, and the accretion was 57 cm during 2006.7-2007.7. Conclusion： （1） the abundant sand-digging on the sand ridge of south channel leads to the adjustment of the flow sections, which might cause the accretion in the deep channels sideward; （2） the intensively accretion during 2006.7-2007.7 in the main channel of South Channel （including the new harbor of Waigaoqiao ） is related to the water discharge change in the extreme drought year; （3） as a passage to the transportation of sediment, the fluvial process of the South Channel doesn’t show good response to the decrease in riverine sediment supple. The main inducement of the change may based on the runoff variation due to the extreme climate event in basin, anthropic activities and the adjustment of the channel itself.