近期长江河口南槽冲淤变化与微地貌特征

Recent processes of morphology and micro-topography in South Passage of the Yangtze Estuary

2015年2月1-7日采用多波束测深系统对长江口南槽河段进行走航测量,结合人类活动强干扰下的海图水深数据及河槽表层沉积物资料,探讨近期长江河口南槽河段河槽冲淤变化与微地貌特征。结果表明:在三峡工程等流域大型工程和深水航道治理工程等河口工程的共同影响下,近期南槽河段上段持续受到冲刷且冲刷态势向下延伸,在1995-2013年南槽河段(中下段和口外段)共淤积1.96亿m^3,平均每年淤积0.11亿m^3;2002-2013年南槽河段(上段至口外段)共冲刷4.98亿m^3,平均每年冲刷0.45亿m^3;在其冲刷环境的影响下,近期南槽底床上除发育平滑床底外,还广泛发育冲沟和凹坑等侵蚀性微地貌,而上段河槽持续受到冲刷导致底沙推移质运动增强,发育了小区域的沙波微地貌,这是首次在南槽观测到的沙波。

Morphological processes and micro-topography features in South Passage of the Yangtze Estuary is studied,based on the bedform date in February 2015,with the acoustic multi-beam bathymetric,the chart date,and surface sediment samples collected recently. Results show that the upper bed in South Passage of the Yangtze Estuary has suffered more serious erosion,and with a trend downward,due to dam projects in the Yangtze drainage basin and the Yangtze Estuarine Deep Navigation Channel project. It is concluded that the South Passage was characterized by scouring from 2002 to 2013,the volume of sediment scouring being 4. 98 ×10^8m^3and the mean volume of annual scouring being 0. 45 × 10^8m^3. In addition to smooth bedfloors,there are erosive micro-topography in the North Channel,such as hollow and gully etc. Moreover,the bed subject to erosion will lead enhancement of bed load movement in favor of the development of sand waves,and the sand waves are firstly discovered in the South Passage.