Features and formulae of sediment incipient motion in vegetated flow environment

Aquatic vegetation is a vital component of natural river ecosystems, playing a crucial role in maintaining ecological balance, providing habitat and improving water quality. However, the presence of vegetation results in increased resistance in vegetated channels compared with non-vegetated channels, rendering traditional sediment movement predictions inadequate for the latter. Consequently, the concept of a vegetation influence factor, denoted by C_Dah, has been proposed by previous researchers to represent the effect of vegetation on sediment movement in watercourses. In this study, we focus on exploring the vegetation resistance coefficient (C_D) among the vegetation influence factors, evaluating two different calculation methods for vegetation resistance coefficient, and presenting two expressions through genetic algorithm analysis to predict the incipient flow velocity of sediment in vegetated watercourses. The predicted values from the new formulae show excellent agreement with measured data, highlighting the high accuracy of the proposed methods in predicting the incipient flow velocity of sediment. Our results provide a solid theoretical basis for understanding the influence of aquatic vegetation on sediment particle movement.