基岩海岸围填海工程后的流场变化

Preliminary study of the flow field variation resulted from reclamation project at bedrock coast

对舟山岑港北侧基岩海岸围填海工程前(2006年)、后(2008年)水文测验资料进行对比分析,得到该工程所在海域潮流场变化的初步结果。用数值试验的方法进行数值模拟,预测围填海工程对周边海域流场的影响,并对流场预测结果的可靠性进行了分析和讨论,结果表明:(1)利用数值模拟方法对海岸围填海工程后潮流场的预测结果基本上能如实反映实际工程后的潮流场变化情况;(2)围填海工程对潮流场的影响范围主要集中在围填海堤的前沿,围堤附近的流速减小,在离围堤一定距离的小范围海域,流速增大,随着离围堤距离的增大,围填海工程对潮流场的影响逐渐减弱;(3)为全面反映工程海域的潮流场状况,应合理布设水文观测点的断面分布,这对模拟工程所在海域的流场将起重要作用。

Local changes of coastal topography resulted from the construction of sea walls influence the hydrodynamic conditions of the surrounding sea area of the reclamation project,and form a new trend of scour and silting.Study on the changes of the tidal flow field caused by reclamation project is an important content of marine engineering science,as well as marine environmental impact assessment and authentication of the use of marine area,which provides basis for engineering design.Numerical simulation has been widely used to estimate the tidal flow field after the reclamation project and thus judge the advantages and disadvantages of the project,which plays an important role in the project construction.However,comparative study of the predicted results and in situ measurements is still rare.Based on the data from the reclamation project north of Cen Gang,Zhoushan Islands,the impact on the surrounding flow field is studied,which is of value to the comprehensive assessment of such projects.Firstly,comparative analyses of the hydrological observation data before（2006） and after（2008） the project were carried out,which results in the variation of the observed flow field.Using the observation data in 2006,numerical simulation of the flow field was made,which resulted in the flow field before the implementation of the reclamation project,and then the changes were estimated according to the scheme of the engineering project,of which the results were compared with the hydrological observation data in 2008 after the implementation of the reclamation project,and the reliability of the predictions is thus verified.In the study,four fixed hydrometric stations in front of the dike in June 11~12,2006 and April 7~8,2008 were set to observe the flow velocity and directions during high tide every 10 minutes continuously for 26 hours at six-points（surface,0.2 H,0.4 H,0.6 H,0.8 H,bottom）.The distance between the hydrometric stations 1~4 and the embankment line was 150~220 m for the two observations.Delft3D-flow was used for the numerical simulation,and the hydrological observation data from 2006 were used to verify the model,determine the parameters and establish the model.And the models were used to predict the flow field,of which the results were compared with the hydrological observation data from 2008 after the completion of reclamation projects to verify the reliability of the numerical model.The study area is along the coastline of the chemical industrial zone at Cengang town,Dinghai Distric,Zhoushan city.The coast is characterized by bedrock and twisted shoreline with island reefs.It＇s a small reclamation project with an area of about 240 mu（about 16 hectares）.The coastline of the project area is northwest—southeast in direction.In the front of the reclamation area is Guci sea-route,and the Fuchi island in the south divides this waterway into two branches： the west branch near Cezi island is Taoyao sea-route;the east branch near Diaoshan island is Xiangjiao sea-route.To the north of Fuchi sea-route is Cezi sea-route,through Hengshuiyang further north to the Hangzhouwan Bay.Large vessels can pass through Jintang waterway,Luotou waterway and Cezi waterway.