LARGE-SCALE WAVE BASIN EXPERIMENTS ON THE INFLUENCE OF LARGE OBSTACLES ON TSUNAMI INUNDATION FORCES

Tsunami runup and lateral force on an instrumented specimen fronted by macro-roughness elements representing were determined experimentally in a large-scale wave basin. Eight different setups of macro-roughness were examined by varying the number and spacing of elements and the distance between the elements and instrumented specimen. Variations in the grouping of macro-roughness elements produced were shown to affect the specimen response. A single macro-roughness element and a pair of macro-roughness elements (spaced one unit width apart in the alongshore) show opposite trends in the peak force as the distance between the macro-roughness elements and the specimen is decreased. Keeping the number of macro-roughness elements constant and increasing the alongshore spacing caused the force and runup on the specimen to exceed the baseline values in several groupings. Finally, keeping the number of macro-roughness constant but varying the spacing of the outer two elements gave an overall reduction in maximum force and a substantial reduction in force for one of the groupings. These results suggest that the relative spacing of neighboring buildings could have substantial influence on the tsunami inundation forces further inland.