Numerical Simulation On Hydrodynamic And Sediment Environment Effects Of Reclamation Projects In Meizhou Bay Based On EFDC

Reclamations are the inevitable realistic needs of urban development in China,and bring tremendous social and economic benefits to our country.However,a large area of reclamation leads to a sharp decline in fishery resources,serious degradation of ecosystems and reduction of biodiversity.The reclamation changes the shape of the coastline,resulting in the decline of water exchange capacity and the reduction of environmental carrying capacity.It is of great significance to study the impact of reclamation on water and sediment environment in specific sea areas for coastal planning,regulation and ecological protection in Fujian Province.Based on EFDC,a three-dimensional hydrodynamic,temperature,salinity,sediment and wave model of Meizhou Bay is established.Tidal level is used to drive the boundary,and the effects of bottom roughness,turbulence coefficient,wind and meteorological factors are taken into account.The model considers only one component of cohesive sediment,and the parameters of illite are taken as the basis of adjusting parameters.At the same time,the sediment coming from the sea,the subsidence erosion of the bed and the influence of wave are taken into account.In this paper,the tidal data of T1-T3 stations and the data of velocity,flow direction,temperature,salinity and sediment of C1-C6 stations are used to calibrate the model.Results showed the overall simulated results of the model agree well with the measured values.Meizhou Bay is dominated by the regular semidiurnal tide with a phenomenon of diurnal inequality and the path of fluctuating tide is consistent.The range of temperature is 20~25 ? in summer and 7~14 ? in winter,but their distribution is the opposite.The salinity is low inside and high outside in both summer and winter,but the distribution in winter is more uniform.And the range of sediment concentration is 0~0.08 kg/m~3 in spring tide and 0~0.05 kg/m~3 in neap tide.In neap tide,the sediment concentration in the central channel is higher than that in other areas,which is more significant than that in spring tide.In addition,the effect of wave on sediment concentration is negligible in spring tide.The wave increases sediment concentration by 0.04~0.05 kg/m~3 at 8 bay bottoms in neap tide,but the sediment concentration in other areas has hardly changed.Moreover,after the reclamation,the tide level difference will increase obviously and the velocity will decrease by 18~55%,it means the hydrodynamic force will decrease obviously.The change of temperature is-0.6~0.9 ? in summer and-2.1~1.4 ? in winter,and the reclamation causes the salinity to rise inside and decrease outside.The change of salinity is-0.44~0.61 PSU in summer and-0.11~0.24 PSU in winter.About 70% of the total area of Meizhou Bay,the sediment concentration is decreased and the bed thickness is decreased,too.However,most of the original sediment carried by the water is concentrated at the southeastern side of the Meizhou Island,which leads to the increase of sediment concentration and bed thickness in the water outside the Meizhou Island.