VOLUMETRIC SEDIMENT CONCENTRATION IN DEBRIS FLOWS

Volumetric sediment concentration is a vital element in the study of debris flow as it affects formation, movement, deposition, flooding zones and damage scopes of debris flows. Based on the mechanical theory of sediment layers from gully's infinite slopes and the incipient law of sediment particles on stationary beds, a generalized formula to calculate the volumetric sediment concentration is developed in this study. Compared with this formula using data obtained from Takahashi's and Ou's flume experiments and discovered that when the critical flow parameters are at 0\^05 and 0\^15 respectively, the formula can simulate the regularities of the volumetric sediment concentrations at the flow forefront as well as the average sediment concentration, which changes in correlation to the gully\|bed slopes. Finally, this study proposed using volumetric sediment concentration as well as gully\|bed slopes as the two parameters distinguishing debris flows from sediment\|laden flows.