The Distribution Of Surface Suspended Sediment And Its Dynamic Mechanism Analysis Based On Landsat Images In Yellow River Estuary

Suspended sediments influence the evolution of the estuary, coastal landform,environment and ecology, fishery and aquaculture,and deposition in ports and waterways. Establishing the inversion model for high surface suspended sediment concentration(SSSC) in Yellow River estuary has great practical application values to the development planning of the Yellow River delta area and the coastal protection. In this study, the characteristics of reflected spectrum of suspended sediment in the laboratory with different concentration are analyzed. The SSSC ranges from 1 to 5700 mg/L and increases mainly by segmentation arithmetic progression.The samples of sedimen and seawater used in this experiment are collected in the low reaches of the Yellow River and Laizhou Bay,respectively. Then the remote sensing parameter of SSSC is selected to establish the retrieval mode of Yellow River estuary. And the retrieval mode is compared with the published models.SSSC is retrieved from Landsat TM/ ETM+/OLI images in Yellow River estuary using the models that are built based on the data of experimental simulation.The distribution characteristics of the surface suspended sediment in Yellow River estuary since 1996 are summarized. The distributions of the surface suspended sediment in wet season and dry season since 2006 are compared. When the satellite was passing,the diffusion process of the surface suspended sediment and its dynamic mechanism are analyzed, combining the TPXO tidal model and ECMWF data. The thesis has the following results.1. The spectral reflectance increase with the increase of SSSC,but the increasing extent was different. The wavelength regions(740-900nm) are most sensitive to the changes of SSSC and less susceptible to the effects of the spectral reflectance saturation, when the SSSC is greater than 2700 ㎎ /L.Therefore,they are more suitable for the high sediment retrieval. The water reflectance and SSSC at 726-900 nm are highly correlated.The SSSC has much higher correlation coefficients with near-infrared bands than visible bands and the correlations are lower in shorter wavelength regions(from 400 to 550nm) of visible bands.2. The retrieval model was established using the ratio of the 820 nm and 490 nm as factor. Comparing the cubic model built in this study with the published models,the cubic model is better for the high sediment.The ratio of a near-infrared band(740nm<wavelength<900nm)and one visible band(wavelength<600nm) as factor, results in robust quantification of high SSSC. The cubic models are built based on the Landsat TM/ ETM+/OLI bands corresponding to the 820 nm and490nm wavelengths,which can reflect the distribution of the surface suspended sediment in Yellow River estuary very well.3. The suspended sediment in northern Yellow River Delta can supply the south regions under the combination effects of the strong northwest wind and flood current. But in most cases of flood tide, the sediment can’t diffuse to the southwestern shore of Laizhou Bay.In the ebb,party of the sediment from the Yellow River spreads to the deeper waters and supplies low to the the shallow waters in northern Yellow River Delta.4. There are three higher SSSC areas, which are located in Yellow River estuary,south-western Laizhou Bay and northern Yellow River Delta. The distribution and diffusion rangeof high SSSC vary because of the tide,wind direction and speed.In general,the diffusion range and average concentration of the surface suspended sediment in dry season are greater than them in wet season.5. The sea area deposits most of the sediment from the Yellow River within 5 m depth contour and the diffusion scope of the sediment discharge into sea is within15 m depth contour because of the high velocity zones, tidal shear fronts and mouth vertical circulation.Part of the sediment deposits on either side of the mouth,which makes the famous north-south mud area.6. The sediment discharge into sea at flood tide mainly spreads to the south,with the sand of abandoned estuary of Qingshui River,diffuses to the Laizhou Bay southwest,but it can’t diffuse to the shore.There is clear water near the shore of Laizhou Bay southwest.It flows offshore. In the ebb,it flows offshore.The water containing high sediment of Laizhou Bay spread outward through the middle of the Laizhou Bay.And there is also clear water in southwestern shore of Laizhou Bay.