Granular flows through a model-scale forest: Influence of tree density and implications for landslide mitigation

Abstract

Landslides pose a severe threat to the man-made and natural environment. As a result, many different artificial structures have been employed to attempt to mitigate the damage from these hazards. However, natural systems, such as forests of trees, can also play a defensive role by dissipating energy and reducing flow speed. This study uses a small-scale model forest to investigate the effectiveness of such sustainable measures. It examines how granular flows interact with arrays of tree structures at different densities, comparing the results to flow down a bare plane. Using image analysis of high-speed camera recordings, we track the lateral spread-out area and the speed of the flows. The results show that the trees have a strong decelerating effect in the downstream direction, and also slow the rate of lateral spread out. The knowledge gained from these experiments can be applied to the field scale, and could provide useful practical guidelines for alternative, sustainable hazard mitigation in mountainous areas.