Study On The Yangtze River’s Resistance Changes In Three Gorges Reservoir Area

The sediment problem of The Three Gorges Reservoir Area be concerned in research of domestic academia. Resistance changes in the reservoir area is an important aspect of the sediment problem, has always attracted attention by the researchers, but the resistance in the trunk stream of the three gorges reservoir area study only limited to the specific conditions of the local river. And the previous research data are before 2003, outdated information is insufficient to reflect the resistance change of trunk stream l after hub of the impoundment of the reservoir area. So the study resistance changes in trunk stream of The Three Gorges Reservoir Area, has important significance for the new situation requirement.In this paper, Using measured data analysis methods analyze the characteristics of scouring and silting of the trunk stream of the Yangtze River in The Three Gorges Reservoir Area, using MIKE11 hydrodynamic module established the one-dimensional hydrodynamic model for the section, Through the passing rate constant obtained the roughness under each flow rate for the section of the trunk steam. The GIS technology, nonlinear geometry, fractal theory is introduced into river dynamics and quantize the library thalweg longitudinal profile and the key segment of the reservoir bed form, discuss the effect of the resistance in the Three Gorges Reservoir Area of Yangtze River trunk stream morphology erosion adjustment, and take this as the foundation of River comprehensive resistance calculation method were studied. The main contents and conclusions are as follows:1, Since 2003 the impoundment of The Three Gorges dam, The Three Gorges Reservoir Area longitudinal profile changes, even in the local river range has obvious changes, but this does not change the basic form of river thalweg in The Three Gorges Reservoir Area. The most sediment deposition in the reservoir within 145 m below the water capacity. The trend of the development of the reservoir sedimentation has upstream. Especially in fuling scour by the natural conditions for the section above turn to fill deposition, and the proportion of sediment deposition is increased. 2,After the impoundment of the reservoir roughness multi between 0.043, 0.085, under various flow rate, of each segment along the roughness showed the following characteristics: near the dam segment by effects on the dam was general roughness larger; Padang roughness for the section above, there are upstream decreases gradually; The roughness for the section has the trend of decreasing year by year.3,For the Yangtze River Three Gorges Reservoir Dam ~ Badong、 Badong ~ Fengjie、Fengjie ~ Yunyang 、Yunyang ~Zhongxian、Zhongxian ~ Lidu the thalweg of each year go ahead fractal quantization Analysis, obtain Box-dimension of each year in each segment of the reservoir. Found there are negative correlation between the segment of the reservoir sedimentation volume(volume) and thalweg Box-dimension(TD) amplitude; conclusion a formula according to the thalweg Box-dimension roughly estimated channel roughness;4, Combined with GIS technology established The Three Gorge Reservoir Area of key reach Qingyanzi reach, Tunaozi reach, lanzhu bar, Fengwei dam, Huanghuacheng resch of 3D underwater digital map, and for quantifying the fractal shapes of a base segment, calculated the number of each year the Reservoir sctions of the bed surface fractal dimension(BSD). Through the analysis of the erosion found that the bed surface fractal dimension of annual variation can reflect evolution type of the overall channel scour and silting.5,Through the analysis of the relationship between the bed surface morphology and roughness N, this paper establishes the functional relationship between roughness N and BSD, and the reliability of this formula is verified, the results show that the high precision formula can be used for the actual roughness estimation.6, Based on the fractal theory, the introduction of thalweg elevation standard deviation for the equivalent roughness, established a bed surface fractal dimension BSD, river thalweg elevation standard deviation formula for computing roughness n value. This formula compared with Manning formula solves the problems of the dimension is not harmonious, compared with other estimation formula of roughness N, the formula considering the whole boundary condition effect on roughness, with a certain degree of progress.