Retrieval And Analysis Of Surface Suspended Sediment Concentration By Remote Sensing In Yangtze River Estuary

Observing of Suspended Sediment Concentration is vital for management of coastal environments in coastal zone and estuaries. Field-measurements carried out to collect information of SSC were usually expensive and point limited. Remote sensing data are among the most important data sources for monitoring and extracting suspended sediment concentration in near-shore coastal Case 2 waters for its high spatial resolution and temporal advantage.This study is carried out in Yangtze River Estuary and adjacent waters.1) Field measurements with an ASD Field Spectrometer were carried out to acquire the reflectance hyper-spectral data of the case 2 waters in Yangtze River estuary. Meantime surface water samples at 0.5 m depth were bottled for suspended sediment concentration (SSC) measurements in the laboratory. The current velocity and water turbidity were also measured in synchronization with the spectral measurements.2) The remote sensing reflectence were calculated from field-measurement data and processed by moving averaging and the first derivatives calculation.3) The characters of spectrum were analysed. With the least-squares method, the regression models were established between SSC and the spectral reflectance at wavelengths corresponding to different bands of AVHRR, MODIS and TM data with an exponential function and a power function, respectively.4) The remote sensing data were corrected and converted to reflectance.The SSC of case 2 waters were calculated from remote sensing data of AVHRR, MODIS and TM.The findings and conclusions for this paper show as,1) Observing the processed curves, we found that the reflectance amplitudes vary with SSC values. There exist two peaks located in yellowgreen (560-720 nm) and near-infrared bands (790-830 nm), respectively. At wavelengths above 500 nm a strong correlation exists between spectral reflectance and SSC in situ measured. At wavelengths 690-830 nm, the reflectance is sensitive to SSC variations and the correlation coefficient is above 0.8.2) The models show that the exponential function and the power function at 715 nm and 810 nm have higher determination R~2. It is noted that the regression models established with reflectance at 670 nm, 715 nm and 800 nm with respect to SSC have better estimation accuracy for SSC than other models.The different wavelengths or bands were selected from AVHRR, MODIS and TM to calculate the SSC.3) The SSC computed from MODIS , AVHRR at different time in the same place were used to monitor the suspended sediments distributions The rtesults show that the distributions of SSC are different in summer and dry seasons with the changes of river runoff flow and tidal flow. It is noted that the patterns of sediment distributions in Yangtze River estuary changes clearly with the runoff in different years.