长江口南支涨潮槽新桥水道冲淤变化的定量计算

Calculation of the amount of siltation and erosion in the Xinqiao Channel of the South Branch of the Changjiang Estuary in China

根据1861～2002年100多年中的15幅海图资料，以GIS技术为支持，建立不同时期长江口水下数字高程模型（DEM），对长江河口南支涨潮槽新桥水道进行了冲淤变化的定量计算，并对比计算了多年来新桥水道0m岸线和5m等深线以及横断面的演变．计算结果显示在所研究的区域内自1861年以来新桥水道冲淤过程明显被分为三个阶段：1861～1926年的66a间新桥水道区域经过一段时间的冲刷后又重新产生淤积，总容积变化不大；1926～1958年的33a间新桥水道在不断的冲刷中总容积由2．603亿m^3增长到5．076亿m^3；1958年至今的45a时间里水道容积基本保持在平均5．02亿m^3．1926年新桥水道10m等深线已经形成一定的格局．1947年5m等深线向上延伸，扁担沙已经不再与崇明岛相连；1958年上下扁担沙的5m等深线基本连成一体，可以认为此时新桥水道已经形成．从新桥水道的横断面变化来看，其主泓不断发生变化，主泓经历了向北移的过程，移动约为1．1～2．8km．

Supported by GIS, 15 pieces of charts of the Xinqiao Channel of the South Branch of the Changjiang Estuary are studied. Digital elevation model of the Changjiang Estuary is established with Kriging gridding method to research evolution of channel change of coasts, formation and evolution. The different points of views, transverse section, plane and volume changes are considered. The results show that the evolution of the Xinqiao Channel has experienced three stages： in 1861～ 1926, the Xinqiao Channel area had been eroded at first and then silted; the Xinqiao Channel is formed during 1926～1958 with the channel experiencing persistence erosion; from 1958 to 2002, the total volume of the Xinqiao Channel keeps stable with the volume of 5.02 × 10^8 m^3. The pattern of 10 m contour has shaped to a certainty in 1926 and 5 m contour of the upper and lower parts of Biandansha has been joined. The change of sections of the Xinqiao Channel reflects its thalweg movement to the North Bank 1. 1～2. 8 km, its shape changes from “U” shape to “V” shape and its depth has been deepened. The evolution of the Xinqiao Channel from 1861 to 2002 is predicted that the channel will keep stable for a long time as soon as the Changjiang Estuary maintains its configuration.