The effects of a drop in a vegetated channel on the flow characteristics during a dam failure were investigated using a numerical approach. A CFD package was used for all dam failure simulations. After performing validation tests, the model was used to predict the flow characteristics during a dam failure over a vegetated channel with positive, negative, or no drop. A positive drop resulted in a backflow into the reservoir with a negative discharge of Qbackflow=−0.01 m3/s. Even in the channel with no drop, backflow into the reservoir occurred in the last stage due to the drag effect of the vegetation. The maximum discharge occurred at the peak time tpeak = 2.5 s above the drop for all models. The peak discharge decreased from Qpeak = 0.037 m3/s to Qpeak = 0.032 m3/s with increasing positive drop height. However, a negative drop had no significant effect on peak discharge values. In most cases, the maximum flow velocity was around um = 2 m/s. The maximum eddy values decreased by Δωmax =500 1/s for the positive drops and increased by Δωmax =700 1/s for negative drops at the middle stage
