DOI: 10.17603/ds2-w6cr-s920
title: Tsunami-driven debris experiment with varied density group conditions
title: in Experimental study of debris transport driven by a tsunami-like wave

description: Water-borne disaster debris can exacerbate the damage on the built-environment through debris impact and debris damming loads and by decreasing the functionality of infrastructure systems after these events. Therefore, an understanding of disaster debris transport is essential for disaster management. In this paper, an experimental study of tsunami-driven debris advection over a flat testbed was conducted considering different density conditions of debris elements. Debris elements of different two different materials (densities) were considered various debris groups and starting orientation. The final dislocations and local velocity of debris elements were measured optically and compared to flow velocity. It was found that the debris elements of higher density affected the mean longitudinal displacement of the less dense debris, but the converse was not true. Also, it was found that the initial orientations of the debris groups had no measurable impact on the final displacement. The effects of obstacles on the passage of debris and the probability of collision to obstacles were examined and the process of debris-debris and debris-obstacle interactions from debris entrainment to final dislocation was studied. It was found that the less dense debris had a higher probability of collision with the obstacles compared to the more dense debris case.  However, when the debris types were mixed, the less dense debris had a lower probability of collision. Finally, the characteristics of debris dislocation and velocity fields under various density conditions as a group were also evaluated. The reflected wave and interaction among different debris play a role in the probability of collision. However, the density of each debris element was a dominant factor in determining the collision probability.
description: It presents an experimental study of tsunami-driven debris transport over the flat testbed. We utilize two types of debris elements, which have the same shape but different material (wood, HDPE) to create debris of different density. We considered variations in the grouping of debris (wood only, mixed wood and HDPE, and HDPE only), parameterized by the mean specific gravity (SGg). The final dislocations and local velocity of debris elements were optically measured and compared to flow velocity. The effects of obstacles on the passage of debris and the probability of collision to obstacles were examined and the process of debris-debris and debris-obstacle interactions from debris entrainment to final dislocation was studied. The curated data could be utilized to understand initial debris entrainment, and espeically utilized to verify/validate a numerical debris transportation model.  
This work highlights the importance of considering debris density in estimating the longitudinal distance and spreading angle. These variables were less dependent on the initial configuration of the debris field.  Future studies should consider other aspects of the phenomena, including a better understanding of the potential impact by debris on obstacles, the role of the return flow in determining the debris trajectory, and investigations of the obstacles that more realistically reflect urban shorelines subjected to strong overland flow.