Evaluation of buffer block effectiveness in tsunami force reduction: An experimental approach

Coastal infrastructure faces serious risks due to flow induced by coastal hazards like tsunamis and storm surges, necessitating the development of efficient and cost-effective mitigation strategies. Micro-roughness elements, called buffer blocks (BB), have emerged as a promising solution for attenuating flow energy, offering an alternative to large-scale protection structures. Systematic laboratory investigations were conducted with the rectangular-shaped BBs to explore the effect of blockage ratio (BR) along the width direction, longitudinal spacing (LS) in the flow length direction, and the number of rows (NR) on the tsunami force reduction on a shorefront building positioned behind the BBs. Results reveal that both the Froude number (Fr) of the incoming bore and relative bore depth ( R = h/H BB, where h is the free flow bore height and H BB is the height of the BB) significantly influence force reduction in the presence of BBs. Among the BB configurations tested, the force reduction is notably affected by the parameters, BR and NR, with optimal performance being observed for BR = 0.5 [-] and NR = 3 [-]. LS is found to have a lesser impact. This configuration balances performance, material use, and human mobility in extreme scenarios. This study provides the basis for understanding the practical insights for the spatial design of BBs to enhance coastal protection in the event of the above-stated coastal hazards.