The V-shaped channel is one of the widely used drainage channels

whose V-shaped design is conducive to the transport of debris flow and can prevent the accumulation of debris in a channel.However

in the calculation of debris flow velocity

the resultant gradient is empirically guided to employ the vector c of the transverse and longitudinal slopes with the same weight in the summation formula.This weighting leads to an unreliable result

causing the debris to be frequently deposited in the channel

which makes it difficult for the flow to accelerate to its full potential.Therefore

to investigate the different influences of the transverse and longitudinal slopes on the debris flow velocity in a V-shaped channel

25 groups of model experiments under different combinations of transverse and longitudinal slopes are conducted in this study.The differences and causes are analyzed

and the results reveal that both slopes are positively correlated with the flow velocity

of which the transverse slope exhibits a weaker effect than that of the longitudinal one.On the basis of the 25 groups of laboratory test data

a formula for calculating the debris flow velocity in a V-shaped channel is established

and the weights of the transverse and longitudinal slopes in the velocity formula are estimated to be 0.75 and 1.30

respectively.These results verify that the weight of the transverse slope in the resultant gradient in a V-shaped channel should be lower than that of the longitudinal one

which provide methods and references for the optimization of future research on V-shaped channels.