An Investigation Of Suspended Sediment Distribution Changes Induced By North Dyke Of Meishan Waterway Based On Remote Sensing

In recent years,in order to meet the needs of economic development and social development,the marine industry develops rapidly and the degree of marine development and utilization gradually increased,many large marine projects such as bridges and dams were constructed in the costal water of our country.It is urgent to understand the impact of marine projects on suspended sediment factors in the marine environment.As one of the important parameters of water quality,suspended sediment is of great significance to the characteristics of sea water and the marine ecological environment.The remote sensing has gradually replaced the traditional measurement methods for the monitoring of the suspended sediment distribution with the advantage of long-term and synchronous observation over large areas.Using Landsat Thematic Mapper / Operational Land Imager and GF data,this study analyzed the changes of suspended sediment distribution caused by the North Dyke of Beilun Meishan Waterway in Ningbo,Zhejiang Province.Main results contents in this paper are the followings:(1)Based on two dimensional tidal current numerical simulation acquired from FVCOM,the flow direction was from southwest to northeast at the time of flood tide in Meishan waterway.During ebb tide,the flow direction was in contrast with flood tide.(2)We selected two locations on both sides of the dam to extract spectral profiles from satellite images.The pixel values of the water in the near infrared band are extremely low and pixel values between the paired points on opposite sides of north dyke in the near infrared band tend to be consistent.The variations of the pixel values maybe the difference in water spectral characteristics,and the construction of north dyke bring changes in the suspended sediment concentration.It is further explained that the near infrared band is the sensitive band of suspended sediment,and the variation of pixel values was caused by the changes of suspended sediment concentration(SSC)in the water after the dyke built.(3)The inversion model of suspended sediment built by the measured data and remote sensing images explored that the SSC was reduced 50-150mg/l compared with that before the embankment construction,the phenomenon of "clean water" appeared,it has an obvious sedimentation in the estuary of Meishan waterway and near the Meishan Bridge.(4)The construction of the North Embankment brought changes to the tide and hydrodynamic environment in the surrounding sea area,which affected the transport process of suspended sediment and the process of re-suspension and influenced the distribution of suspended sediment.