Comparison Of Formulae For Bed-load Transport In Upper Yangtze River And Safety Design Of Sediment Control

Bed-load transport is a very important element of sediment transport and it affects on the fluvial process. The bed-load transport problem of natural channels and irrigation channels is very common in river engineering. And the sediments of these channels, especially of mounting river of southwest China, are general of different sizes and large ranges of grain sizes. The choosing of better formula for bed-load transport in mounting river is needed, and it can be well used for river engineering. In 1879 Duboys offered a bed-load model with shear stress approach. Duboys'equation is one classical equation. Later many investigators gave new bed-load equations with shear stress, energy slope, velocity, probabilistic and so on approaches. Now there are more than 50 different bed-load equations. Exiting formulae for transport of non-uniform granulometry are most based on those of uniform granulometry. And some of them are used without change. For a non-uniform granulometry, it can be broken down into its fractions. And for a quasi-uniform granulometry,a equivalent diameter can be taken. Nevertheless, the study of transport of uniform granulometry hasn't been well developed, so when these formulae are applied to non-uniform granulometry, especially to that of mobile bed, error will occurs. For mounting river, the bed material is most made up of gravels, cobbles and few boulders. Large particles are not eroded until a previous flood event occurs. These particles that remain at the bed surface are the important part of resistance to flow. Because of erosion and deposition, bed forms are varied and the large particles are in scale-work. So the transport of non-uniform granulometry in Upper Yangtze River is even complex. And in this paper, the formulae for transport of non-uniform granulometry that is better for Upper Yangtze River will be selected. So some formulae are compared with measured data from laboratory flumes and rivers, with emphasis on river data for engineering application. There are many hydraulic power projects and other projects on the rivers, and their safety and normal working condition is affected by the bed-load sediments. If the bed-load sediments exceed the acceptable amount, safety misadventure in sediment control will occur. The ripple frequency of bed-load transport rate is used as the risk ratio of sediment control for the testing of sediment control safety design. The different risk curves for sediment control safety design are offered corresponding to bed-load transport rate that is calculated by the different formulae.