Suaeda heteroptera (S. heteroptera) is the most common indicator plant of solonchak in coastal wetlands of the Liao River Estuary, the influence of meteorology, hydrology environment on vegetation distribution is of growing interest. With the help of satellite remote sensing (RS) technology and geographic information system (GIS), we investigated the spatial-temporal distribution and area change of S. heteroptera in the wetlands of the Liao River Estuary from 1997 to 2016, and the identification of the main driving mechanisms in the S. heteroptera evolution was analyzed in this coastal wetland. The SPSS Statistics 22 software was used to calculate the correlation coefficients between total area of S. heteroptera and each driving factor based on available long-term (1997-2016) and medium-term (2007-2016) data. Correlation analysis results indicated that the change in S. heteroptera coverage had insignificant correlations (correlation coefficients r=−0.241, r=−0.188 and r=−0.269) with annual mean temperature, precipitation, and sunshine duration, respectively. The results also showed that the growth of S. heteroptera was extremely relevant to runoff from the Liao River from April to June (r=0.889) over the last 10 years. This study revealed that some potential factors, such as river discharge may be related to the large-scale degeneration of S. heteroptera in Liao River Estuary wetlands.

Large-scale flooding causes widespread disaster, and harmful pollutant concentration in water following flood affects public safety and the environment. In this study, a numerical model for solving the 2D shallow water equations and the solute transport equation is proposed to simulate overland flood and pollutant transport caused by floods. The present model is verified by comparing the predictions with the analytical solutions and simulation results; sufficiently high computational accuracy is achieved. The model is also used to simulate flood inundation and pollution spread in the area of Hun and Taizi Lane (HTL) in China due to river dike breaches; the results show that the coupling model has excellent performance for simulating the flooding process and the temporal and spatial distribution of pollutants in urban or rural areas. We use remote sensing techniques to acquire the land coverage in the area of HTL based on Landsat TM satellites. The impacts of changed land use on mitigation of flooding waves and pollutant spread are investigated; the results indicate that the land cover changes have an obvious influence on the evolution process of flood waves and pollutant transport in the study areas, where the transport of pollutants is very dynamic during flood inundation in HTL area. Furthermore, the motion of pollutants considering anisotropic diffusion is more reasonable than that due to isotropic dispersion in simulating pollutant transport associated with the flood in urban or farmland environments.

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An increasing number of marine aquaculture facilities are being placed in shallow bays and open sea. In this study, we present a coupled hydrodynamic and solute transport model with high-resolution schemes in marine aquaculture waters based on depth-averaged shallow water equations. A new expression of drag force is incorporated into momentum equations to express the resistance of suspended culture cages. The coupled model is used to simulate the effect of suspended structures on the tidal current and the motion of a contaminant cloud in the marine aquaculture of the North Yellow Sea, China. Simulation results show a low-velocity area inside the aquaculture cage area, with a maximum reduction rate of velocity close to 45% under high-density culture. The results also show that the tidal currents are sensitive to the suspended cage densities, cage length and drag coefficients of cages. The transport processes of pollutants inside aquaculture facilities are inhibited away from the vicinity of the culture cage area because of the reduction in tidal currents; therefore, the suspended cages significantly affect the transport processes of pollutants in coastal aquaculture waters. Furthermore, the reduction in the horizontal velocity can significantly decrease the food supply for aquaculture areas from the outside sea. The results of this study provide new insight into the planning of high-density suspended facilities for coastal aquaculture activities.