Influence of Macroroughness on Tsunami Loading of Coastal Structures

Abstract

This paper presents experimental laboratory data to show how macroroughness affects tsunami flow as it travels across the inundation zone. The effects of macroroughness have been observed in several tsunamis, most recently in the Tohoku tsunami in March 2011. The hydraulic experiments presented here were conducted at Oregon State University’s Tsunami Wave Basin, which is equipped with a piston-style wavemaker capable of producing long-period waves that best simulate the effects of tsunamis on shore (i.e., long inundation lengths without large offshore wave heights). The basin was set up with a multitiered bathymetry representing a flat beach similar to those seen in the Pacific Northwest of the United States. The experiment was conducted by measuring the run-ups and forces on an instrumented specimen being fronted with macroroughness elements. These elements were systematically positioned around the beach section of the basin, creating multiple configurations to evaluate the effects on the specimen. To best quantify each unique layout of macroroughness, a new measure, the wake clearance angle (