扬子浅滩沙波底形活动性评估
ACTIVITY MAGNITUDE OF THE SMALL-MEDIUM SUBAQUEOUS DUNES IN THE YANGTZE SHOAL
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摘要: 扬子浅滩位于长江口以东,水深40 m左右,普遍发育中小水下沙丘并处于运动状态。按32片沙波参数统计,迁移方向在90°~180°之间,其中150°~180°者占30%,120°~150°者占69%;使用Rubin和改进的Hardisty公式计算,以潮流作用为主的常态海况下,沙波迁移率为19.70 m/a,以浪流为主的暴风浪期间,约为12.72 m/a,一年总迁移率约为32.4 m/a,与世界上若干海底沙波定位观测数据相对比,这一迁移率应属于缓慢-中等的量级。Abstract: The Yangtze shoal, located in the east of the Yangtze River Estuary and about 40 m deep below sea level,has widely spread small-medium subaqueous dunes,whose wave height is 0.6 m and which are generally in activity. Statistical result of 32 subaqueous dune areas shows that the movement direction is within 90°~180°.150°~180° direction accounts for 30% and 120°~150° for 69%. The movement velocity of the small-medium subaqueous dunes, calculated using the formulas from Rubin and Hardisty, is usually 19.70 m/a and controlled by tidal currents, and is 12.7 m/a in storm season.And the total migration rate is 32.4 m/a. Compared with observation data from other small-medium subaqueous dunes in the world, the activity of small-medium subaqueous dunes in the Yangtze shoal belongs to a slow-medium magnitude.