Experimental investigation of tsunami runup reduction in the presence of a coastal dune

Abstract

Tsunamis are one of the most disastrous natural hazards and have a high potential to devastate coastal infrastructure which can result in a notable loss of life. When tsunami waves approach the coast, they cause runup, overtopping, and inundation, which can damage coastal infrastructure and pose a threat to human lives. The tsunami runup is an important factor in the design of coastal protection structures against tsunamis. Therefore, it is essential to predict the runup height of tsunami waves accurately and quickly. From the field observations of past tsunami events at many parts of the world, it was identified that the coastal features like dunes, dense vegetation, and combination of dunes with vegetation, acted as natural buffers and provided protection to the regions behind those coastal features [1]-[6]. In order to study the protective behavior of coastal dunes against tsunamis, laboratory experiments were conducted on a laboratory scale model of the dune (rigid surface) on different plane beach slopes (s) (s= 1/2, 1/5, 1/15 & 1/20). The maximum solitary wave runup (R) was observed on the steep beach slope (s=1/2, non-breaking wave) and the minimum runup was observed on the mild beach slope (s=1/20, breaking wave) in the range 0.05<H/h<0.66. From the experimental results, it was also found that the runup decreases by up to 70% in the presence of the dune due to the additional vertical relief.