Abstract: In line with probability and mechanics theory, a unified formula for the incipient velocity of sediment on slopes (including near bed velocity and average velocity along vertical direction) is deducted by introducing incipient probability and additional mass force in incipient sliding model. The influence of adhesive force and additional downward force among fine sediment particles are taken into consideration. Tested results reveal that calculated data from the formula are well consistent with observed data. The formula is of simple form and good calculation accuracy, hence can be used for the calculation of critical incipient velocity of adhesive and non-adhesive sediment particles on slopes with different dip angles.

Key words: cohesive sediment, incipient probability, sliding model, incipient velocity, unified formula