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1997年枯季和 1 998年特大洪水后期 ,在长江口南支 -南港用直读式海流计和Ende co/YSIInc .1 74SSM流速仪定点测量近底和表层流速大小和方向 ,并采集床面泥沙样品经室内分析得到底沙粒径 ,用声学测深仪和UltraElectronics旁侧声纳仪走航测量床面形态。结果表明 :1 )枯、洪季时落潮流近底和表层流速比涨潮流流速大 ,落潮流周期比涨潮流周期长 ,且洪季落潮流表层流速大于枯季时 ,洪季落潮流周期比枯季时长 ;2 )床面泥沙枯季时为粗粉砂至极细砂 ,而洪季时为极细砂至细砂 ;3)枯、洪季床面上的沙波形态受落潮流控制 ,波高与波长之比值以及背流面坡度较小 ,洪季时沙波波高比枯季时高 ,波长比枯季时长。显然 ,长江口南支 -南港落、涨潮流和床面泥沙粒径及沙波形态的特征均与季节性变化的径流有关。此外 ,在VandenBergandVanGelder ( 1 993)底形稳定相图中 ,作者提出了一个新的沙纹与沙波间的转化边界。
In the dry season of 1997 and the later flood of 1998, the size and direction of the near-bottom and superficial velocities were measured by direct-reading current meter and Ende co / YSIInc.174SSM flow meter in the south branch of the Yangtze Estuary - Nangang, Sediment samples were analyzed for sediment particle size by in-house analysis and the bed morphology was measured with acoustic sounder and UltraElectronics lateral sonar. The results show that: 1) the tidal flow near the bottom and the surface flow rate in the dry and flood seasons are larger than that in the tidal flow, the tidal flow cycle is longer than the tidal flow, and the surface flow rate in the flood season is greater than that in the dry season, Dry season; 2) the sediment in bed is coarse sand to very fine sand in dry season, and the fine sand to fine sand in flood season; 3) , The ratio of wave height to wavelength and slope of back flow surface are smaller. The height of sand wave is higher in flood season than in dry season, and the wavelength is longer than that in dry season. Obviously, the characteristics of the south branch of the Yangtze Estuary, the south port drop, the rising tide and the bed sediment particle size and the shape of the sand wave are all related to seasonal changes in runoff. In addition, in VandenBergandVanGelder (1993) bottom-stable phase diagram, the authors propose a new transformation boundary between sand and sand.