基于潮位含沙量观测数据的乐清湾悬沙交换分析

潮汐作用下海湾内外频繁地发生水体和泥沙交换,可引起湾内地形演变和环境变化。根据乐清湾沙港头测站2003年实测潮位及涨落憩时刻表、底层实测含沙量,采用纳潮量与含沙量乘积计算海湾涨落潮期间泥沙通量,泥沙通量与潮差之间关系可利用幂函数型曲线进行拟合。结果表明,乐清湾涨、落潮泥沙总通量基本持平,拟合曲线表明涨、落潮潮差与进、出海湾的泥沙通量关系总体相近,大、小潮区段稍有差异。冬夏季各月存在一定净通量,但不超过输沙总量的2%。分析认为导致净通量原因主要是潮汐不对称性和涨、落潮期间的含沙量变化,沙港头测站涨潮历时稍长于落潮历时,M_4和M_2分潮振幅比大于0.01,潮波变形明显,潮差在涨落潮期间呈不对称性;表层平均含沙量涨憩小于落憩,底层含沙量涨憩大于落憩,涨、落潮期间含沙量与对应潮差呈幂函数关系,不同期相应幂函数参数有所差异。

Analysis of Suspended Sediment Exchange in Yueqing Bay Based on Tide Level and Sediment Concentration Data

Frequent exchange between water body and sediment occurs in the bay with the action of tide potentially causes the terrain evolution and environmental change. According to the measured tidal level at the Shagangtou Observation Station at the mouth of Yueqing Bay and the measured sediment concentration at the surface and bottom of the rising and falling schedule in 2003, the sediment flux during that schedule was calculated using the product of the tidal prism and sediment concentration. The relationship between the sediment flux and the tidal range could be fitted using a power function curve. The results show that the total flux of sediment in Yueqing Bay is basically balanced, and the fitting curve shows that the relationship between the rising and falling tidal range and the sediment fluxes entering and leaving the bay are similar, while there are slight differences between the large and small tidal sections. There is a certain net flux in each winter and summer, but not more than 2% of the total sediment transport. It is analyzed that the net flux mainly attributes to tidal asymmetry and sediment asymmetry. The flood tide of Shagangtou station lasts slightly longer than that of ebb tide, and the amplitude ratios of M4 and M2 tide are greater than 0.01 in each month, which explains the phenomenon that the tidal wave deforms obviously. The mean sediment concentration of the surface layer during the spring tide is generally less than that of the ebb moment, while a contrary result is attained between the bottom and the surface sediment concentration. There is a power function relationship between the sediment concentration and the corresponding rising and falling tide during the large and small tidal sections, while the parameters of the power function are different in the different periods.