Abstract: Measured the cover soil water content in soil layer 0~30cm of different agroforestry landscape types in Jinghe river with TDR, the landscape types including sloping cropland, apple orchard, apple-clover system, land under forest and grass changed from grain crop and black locust forest. Analyze the distribution characteristic and spatiotemporal variability of the cover soil water. The result showed that the soil water has renewed in a certain extent after a rain period in 1.5 m soil profile; the soil water content is gradually increased from the top of to the bottom of the slope under the affection of the slope location and plant category. The theory model of semivariogram for cover soil water content before rain season and after season, the value of nugget is changed no obviously , and they are 0.25 and 0.30; ranges is 99.7 m and 87.6 m. And the results indicated that soil moisture exhibited high fractal dimensions and clear spatial autocorrelation. The fractal dimensions are 1.71 and 1.74, variogram is main autocorrelation. During rain season the theory semivariogram model is linear, the spatiotemporal variability of soil water content becomes higher with the increase in distance, and its fractal dimension is 1.40.
Abstract: Through analyzing 50-year hydraulic data and by means of water-sediment model of middle reach of Yangtze River for numerical simulation calculation, it studies flow and sediment diversion at Four Inlets of Dongting Lake and tendency and impacts of erosion-deposition variation, and predicts the conditions of Three Gorges Project after 30 years’ operation. It can be found that flow and sediment diversion at Four Inlets of Dongting Lake are decreasing and the zero flow period is constantly prolonged. River courses at Four Inlets and Dongting Lake continue to deposit and shrink, and the problem of water resource in the Dongting Lake area is becoming more serious than before. Operation of the Three Gorges Project has not changed this trend and with the time of the operation goes on, the trends of flow and sediment diversion and erosion-deposition at Four Inlets river courses and Dongting Lake will be more detrimental to the water resources in the Dongting Lake area and its problem will continue to deteriorate.
Abstract: After analyzing the surface-boundary condition of suspended sediment concentration (SSC), Cheng et al. further improved the sediment diffusion coefficient which was proposed by Bose and Dey. Then an improved Rouse law (IRL) was developed. This equation, which has a similar form as Rouse law, not only overcomes the zero concentration at the free surface, but also behaves generally better than Rouse law and van Rijn equation over the whole water depth in the verification analysis. In this paper, the surface-boundary condition of SSC is further analyzed. It is elucidated that IRL satisfies the surface-boundary condition more reasonably than Rouse law. In addition, a first-order approximation of IRL is developed. From this approximation, we can easily get the explicit expression of the depth-averaged SSC without any implicit integrals to be solved numerically or by the help of a chart. This is very useful in the further study of non-equilibrium suspended sediment transport (SST).
Abstract: In order to overcome the difficulties existing in estimating the multiple threshold values in multiple threshold regression models, a new Multi-threshold regression prediction method is proposed using Particle Swarm Optimization (PSO) in this paper, realizing estimating the multiple threshold value of multi-threshold regression (MTR) model. This method expands the prediction factors at the beginning, reduces the dimension using principal components analysis, searches threshold value by PSO and then establishes threshold regression model. A set of common modeling solutions of MTR is presented based on PSO at the same time. And this modeling solution is applied to the prediction of Reference Evapotranspiration (ET0) in the Panjin area. Results indicate this model has high precision for prediction and its application will provide a new means for predicting annual cumulative ET0.
Abstract: It is pointed out that the influence of the time step in the unsteady non-uniform sediment mathematical model must be considered when to calculate the mixed-layer thickness in this article. And then a new method to calculate the mixed-layer thickness is obtained based on the sand wave movement. This method can well reflect the effect of the time step on the mixed-layer thickness, and has a wide field of application in the numerical simulation of natural river sediment transport.
Abstract: The paper reviewed the research and progress of solid materials on the gully system in the world and pointed out the shortage of it. On the condition of hydrodynamics, many papers available concentrated on the relationship between rainfall parameters and debris flow occurrence, rainfall infiltration and surface runoff; while on the solid materials on the gully or slope surface, a lot of researches focused on the flume experiments to analyses the initial condition and debris flow process under hydrodynamic effect together with artificial rainfall. Base on the reviews previous, paper give some prospects of research under hydrodynamic conditions in the futures.
Abstract: The flood in the mountainous area is characterized by remarkable outburst, low foreseeability, sudden rise and sudden fall and large destruction and is one of the natural disasters in rural area. In order to reduce the loss from mountain flood, this Thesis, taking the section of Siwu Village on the upstream of Miaoyuanxi Stream as the study object, conducts the calculation of the design flood for the small watershed of Miaoyuanxi Stream. The small watershed is short of the data of actually measured rainfall, especially runoff; therefore, based on the geographic information system (GIS), with irregular triangle net and spatial analysis function, we have realized the interpolation of the hydrologic characteristic value isoline of the research area; with frequency analysis, we have calculated the design rainfall of different time at different frequency and further calculated the design peak with the rational formula; in addition, with the hydraulic method, we have calculated the corresponding water depth of the three control sections of Siwu Village. The result shows that, the combination of small watershed design flood calculation and the GIS can make the hydrologic calculation more accurate and convenient. The research result may be the reference for the establishment of the flood prevention and avoidance guarantee system for the rural area.
Abstract: By scouring experiments, the changeable process and characteristics of sediment concentration in sloping surface with different coverage degrees and spatial locations of grass were studied. Five grass coverage degrees of 0, 30%, 50%, 70%, 90%, three spatial locations of grass (upslope, mid-slope, low-slope) and two water inflow rates of 3.2L/min, 5.2L/min were applied to a 0.5 by 8 m soil bed in scouring experiments. Results showed that in the hillslope–gully side erosion system, the grass coverage has great effect on reducing the sediment concentration in the overland flow when the water inflow rate is small, but when the water inflow rate is large this kind of effect is very limited. When the grass located at the low-slope on the hillslope the sediment concentration is relatively smaller. The sediment concentration in the overland flow is gradually decreasing with the duration of scouring, and the effect of spatial locations of grass on the temporal variation of sediment concentration is very complicated because of gully erosion.
Abstract: Taizhou Bay is an estuary with high tidel range, middle tidal current and low sediment concentration. For the sea floor is very dense, it is stable in the usual water regimen. The numerical model is introduced to simulate the suspended sediment transport in Taizhou Bay. And the recent hydrologic data and the seabed change have been validated by the numerical model. The movement of tidal current and sediment in Dagagn Bay are simulated, and the sediment siltation in port designed is calculated by the model. The results show that the sediment source is from the shoal produced by the ebb current, and the sediment silting is decreased two-thirds by the cofferdam back of the bay, because the way of the suspended sediment is stopped by the cofferdam from the shoal to the harbor.