Due to the irregular shapes, the dynamics of irregular particles in a rotary drum are more complicated than those of regular particles. In this study, speckle visibility spectroscopy was used in conjunction with a simple imaging technique to investigate the behavior of irregular sand in a rotating drum under the slumping regime. We found that particle rearrangement originates from the upstream side of the granular bed after the avalanche flow. Furthermore, the energy dissipation of the rearrangement is high closer to the upstream side of the active layer. The greater the degree of particle filling, the greater is the amount of energy dissipated by the rearrangement. Finally, we proposed a model to predict the rearrangement after avalanche in a rotating drum. (C) 2019 Elsevier B.V. All rights reserved.