九龙江口-厦门湾悬沙浓度及多岔口潮汐汊道泥沙输运的数值模拟

基于环境流体动力学模型(Environment Fluid Dynamic Code/EFDC)水动力和泥沙模块,该文针对九龙江口-厦门湾水域潮动力强、浅滩面积大的特点建立二维潮流泥沙数学模型并利用实测数据进行校验。模型精简适用,成功反演了该水域的水动力场和悬沙浓度场,并能正确反映浅水区域的水沙运动特征。结果表明:在潮流作用下,厦门湾水体中悬沙浓度由外向内递增,悬沙随着潮流的涨落在湾内外作中-长距离的往复运动。湾内特别是浅滩区,大潮期悬沙浓度大于小潮期且浓度随潮变化明显,小潮期悬沙场则较为稳定。采用抓斗式挖泥船(源强Q=7.5 t/h)在翔安东南侧浅滩疏浚作业对邻近保护区基本无影响,但翔安南部"五岔口"型潮汐汊道存在能远程输运近岸疏浚泥沙的"泥泵式"水动力场,促使形成环绕厦门岛东海域的带状悬沙分布,该文进一步揭示了形成该分布的水动力机制。增大疏浚强度可导致白海豚保护区被污染,悬沙带宽度增大,浓度上升。

Numerical study on suspended sediment concentration in Jiulong Estuary-Xiamen Bay and sediment transport mechanism in tidal inlets with multi-fork

Based on hydrodynamic and sediment transport module of Environment Fluid Dynamic Code/EFDC,a 2-Dimensional mathematical model was applied to the simulation of tidal current and sediment transport in Jiulong Estuary-Xiamen Bay,which was set up with full consideration of the strong tide and large-area shoal in the study area.The model was calibrated and verified using observational data and the simulation results agreed with measured data well,which successfully re-acted the hydrodynamic field and suspended sediment transport in this area,including that of the shoal area.The research shows that,mainly controlled by tidal current,suspended sediment concentration (SSC) increases progressively from outside to inside of Xiamen Bay and suspended sediments move forth and back as tidal currents flow rectilinearly along channels.Inside the bay,especially in shoal area,SSC in spring season fluctuates tidally and is much higher than that in neap season which remains lower and more stable.Dredging in the shoal area positioned to the south east of Xiang'an using grab dredger with source strength of 7.5 t/h almost has no effect on the adjacent protection zone,however,the water area with five-forks positioned to the south of Xiang'an exists a dredge-pump-like hydrodynamic field,through which dredging-produced sediments can be transported in long distance.The special hydrodynamic field leads to the formation of ribbon-pattern distribution of suspended sediments located in the eastern waters of Xiamen island and the hydrodynamic mechanism of it is revealed.Amplifying dredging intensity can result in the pollution of White Dolphin Protection Zone,broadening of ribbon-pattern distribution and increasing of the S SC.