长江口潮沼植物对动力沉积过程的影响
Influence of tidal marsh vegetations on hydrodynamics and sedimentation in the Changjiang Estuary
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摘要: 为探讨潮沼植物对动力沉积过程的影响,在长江口南汇东滩沼泽和邻近的光滩上进行了近底层流速、波浪、悬沙浓度、沉积物粒径和滩面淤积速率等对比实验,并在九段沙潮沼中做了两种先锋植物黏附悬沙的实验.结果表明,沼泽和同高程的邻近光滩近底层平均流速的比值为0.16～0.84;两种环境平均波周期、平均波高和平均悬沙浓度的比值分别为1.4,0.43,和0.71.波浪传入沼泽后,一方面波高大大降低,另一方面变得规则有序.海三棱草和草两种先锋植物群落黏附的悬沙分别达到298和40g/m2.由于水动力降低和植物的捕沙功能,细颗粒泥沙易于在沼泽中沉积下来,导致沼泽环境沉积物明显较相邻光滩细;沼泽中沉积速率加快,侵蚀受到抑制.Abstract: Bottom current, wave height, bottom suspended sediment concentration, sediments trapped by plants, deposits and shoreface elevations were measured on the natural and artificial flats and in the pioneer Scirpus as well as the upper distributed Spartina, respectively, to examine the effects of marsh plants on hydrodynamic and sedimentation processes.The parameter ratios of marsh to its neighboring bare flat in the same contour are found to be 0.16~0.84 in mean current velocity (the average of the whole tidal cycle), and 1.4, 0.43 and 0.71 in mean wavelength, mean wave height and mean suspended sediment concentration at the beginning of the flood, respectively.Waves in marsh are in rows while those on bare flat are solitary.The amount of sediments trapped by Scirpus mariqueter reaches 298 g/m2.Deposits in marsh are found to be much finer than those on the neighboring flat.Erosion is restrained and accretion is quickened in marsh environment through comparing with bare flat.The effects of marsh vegetations on hydrodynamics and sedimentation are related to plant features and the shorew ard distance from the low limitation of marsh.
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Key words:
- hydrodynamics /
- sedimentation /
- tidal marsh /
- Changjiang Estuary
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