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首页> 外文期刊>Estuarine Coastal and Shelf Science >Seasonal variation of hydrodynamics and sediment dynamics in a shallow subtropical estuary: the Ba Lat River, Vietnam
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Seasonal variation of hydrodynamics and sediment dynamics in a shallow subtropical estuary: the Ba Lat River, Vietnam

机译：浅亚热带河口水动力和泥沙动力学的季节性变化：越南巴勒特河

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The Red River is the largest river in the north of Vietnam, transporting 100 million tons of dominantly silty sediment annually. Hydrographic surveys were conducted in the dry and wet seasons of 2000 in its main branch, to determine sub-tidal and intra-tidal river outflow patterns and sediment transport processes, plus their seasonal variation. It was found that stratification is strongly season-dependent resulting in partly stratified conditions in the dry season when the dominant stratifying and de-stratifying processes are tidal straining, tidal advection, and bed-generated turbulent mixing. The wet season is characterized by stratified conditions when estuarine circulation and advection of stratification by tidal currents and river flow are the main stratifying and de-stratifying mechanisms. A salt-wedge type density-driven circulation was observed in the highly stratified wet season, but the estuary is too shallow for development of classical estuarine circulation in the partly stratified dry season. In the dry season, tidal currents dominate flow patterns and sediment is mainly resuspended locally. The magnitudes of maximum inflow and outflow velocities in the river channel are equal because river discharge is compensated for by flood tidal asymmetry, but net sediment transport is directed seaward because the outflow period is longer. In the wet season, outflow velocities are considerably higher and the period of outflow is longer, whereas inflow velocities are low. Sediment transport is dominated by advection processes, rather than by local resuspension, and the estuary is flushed during each ebb period.
机译：红河是越南北部最大的河流，每年运输1亿吨粉质沉积物。在其主要分支的2000年的干燥和潮湿季节进行了水文调查，以确定潮下和潮内河的流出方式和沉积物输送过程，以及季节变化。已发现分层主要取决于季节，导致干燥季节的部分分层条件，主要的分层和反分层过程是潮汐应变，潮汐平流和河床产生的湍流混合。湿季的特征是分层条件，其中河口环流和潮汐流和河水的分层对流是主要的分层和反分层机制。在高度分层的雨季中观察到盐楔型密度驱动的环流，但对于部分分层的旱季，河口太浅，无法发展经典的河口环流。在干旱季节，潮流主导着潮流，沉积物主要重新悬浮在当地。河道中最大流入速度和流出速度的大小相等，因为河水流量被洪水潮汐的不对称性所补偿，而净泥沙输送则指向海，因为流出时间更长。在雨季，流出速度要高得多，流出时间要长一些，而流入速度要低。沉积物的输送主要由对流过程而不是局部的悬浮引起，并且在每个退潮期河口都被冲刷。

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