| Incipient motion is a basic problem about river dynamics and sediment movement, there are many domestic and foreign scholars have studied it. So far, the proposed non-cohesive sediment formulas have been more than 100, but it is very less formula which reflected gravel motion particularly non-uniform gravel in natural rivers. So it has theoretical and engineering application value to research the gravel motion of mountain river follow as the analysis of the power of the gravel particles.The paper studied several forms of sediment formula. By analyzing the stress on the sediment particles, and using logarithmic velocity distribution, obtained the starting formula of drag force; using exponential velocity distribution to get the starting velocity formula; obtaining the power formula from a power perspective, we have known that it is proportional between water power and size of 3 / 2 Th. Most of the natural river flows are non-uniform, but the start and the starting velocity drag force formula for formulas are based on uniform flow up. Therefore, this paper used the formula of starting power to study uniform gravel and non-uniform motion laws.Firstly, by a large drop test and high-precision flume test, analyzing the data of the uniform gravel, obtaining the gravel motion power formula is: Wc = VHJ/(gD3)1/2 =0.16.Secondly, by ordering a large number of non-uniform gravel starting data at Cuntan and zhutuo station, considering the coarsening of the bed, it is thought that the coarser of the composition of river bed, the greater start power required in the case of the same maximum size in bed. Therefore, it is introduced a parameter Db50/Dbmax which reflect the degree of coarse based on the uniform gravel motion formula to get the non-uniform gravel motion formula.Finally, combining with uniform and non-uniform gravel motion data, obtaining starting power formula ( Wc = 0.16×(Db50/Dbmax1.05(gD3)1/2) which reflect the non-uniform flow and characteristics of non-uniform gravel.
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