Breaking and Runup of Transient Long Waves

Cornell University, Ithaca NY

Investigators

Abstract

After the 2004 Sumatra-Andaman earthquake and Indian Ocean tsunami, scientists and engineers have been working together to improve our understanding of tsunami hydrodynamics and to establish early tsunami warning systems and tsunami hazard mitigation programs in the Indian Ocean and the South China Sea. A promising approach to enhance tsunami data is to analyze the sediment deposits. If tsunami deposits can be correlated with water depth, flow velocity, wave characteristics and run-up heights, the dated sediment deposits will allow estimates of times and recurrence intervals of past tsunamis. In order to establish the relation between tsunami hydrodynamics and sediment transport processes on continental shelf and coastal zones, the first step is to investigate the process of wave breaking, turbulence production/dissipation, bottom stress evolution and run-up/run-down flows of transient long waves. Based on observations during the 2004 Indian Ocean tsunami, it is evident that the leading tsunami waves consisted of several (1 -3) breaking long waves. Therefore, this project will conduct a set of comprehensive experiments in which a series of solitary waves is used as the surrogate leading tsunami waves. The principle objectives are: 1. Identifying the dependence of run-up processes on the number of waves in the group, the incident wave heights, and beach slope. 2. Quantifying the wave breaking processes involving single and multiple waves, primarily the turbulent energy and the bottom shear stress and associated dissipation and exploring the potential for statistically steady-state behavior. The Broader Impacts: This research is at the interface between several fields of science and engineering ? oceanography, fluid mechanics, and coastal engineering and will serve as a bridge among them. The detailed experimental data will provide the necessary information for the parameterization of wave breaking, bottom shear stress and flow turbulence in the sediment suspension and transport models. Therefore, the study will have a much broader impact on the establishment of tsunami hazard mitigation programs. The results will also provide guidance for future direction of experiments. The team will continue its long term collaborations with Prof. H. Oumeraci of the Technical University of Braunschweig, Germany and Prof. H. H. Hwang of the National Cheng Kung University, Taiwan. Certain aspects of scale effects can be investigated by repeating some of the proposed experimental conditions in the large wave flumes in their institutes. The project will train one PhD student in experimental techniques, data analysis and numerical methods so that he/she will be capable of performing model/data comparisons. The P.I. has had a good record of involving engineering undergraduate students in research and in publishing technical journal papers, and this project will provide further opportunities along those lines. The project will also support a postdoctoral researcher who will share the responsibility on supervising the graduate student working on the project and will also teach an undergraduate course.