NEESR: Interaction of Tsunamis with Short Waves and Bottom Sediment - Numerical and Physical Modeling

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

The interaction between short ocean waves and long transient tsunamis is studied in conjunction with sediment transport process. This is in keeping with the theme of the study of tsunami-generated processes in concert with natural oceanographic processes, and will be done from two viewpoints: that of the tsunami's effect on the transported and reworked sediment bed; and that of the effect of the sediment load on the transporting power of the tsunami. Numerical modeling will form the backbone of this work, with physical modeling providing data for process study, parameterization and validation. A sophisticated model based on smoothed particle hydrodynamics will be tightly integrated into the experimental plan. Experiments are planned for the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Large Wave Flume Facility at Oregon State University during the first two years. The first set of experiments will focus on evaluating the transport power of the tsunami in order to develop the pickup function and other parameterizations for the transport model. The second set of experiments will investigate full bed evolution. In all experiments, forcing will consist of tsunamis and combined tsunami-swell conditions. Measurements will be comprised of: free surface elevations; near-bottom velocities (from acoustic Doppler velocimeters); sediment concentration (from vertical stacks of optical and acoustic backscatter devices); and vertical velocity profiles (via pairs of upward/downward looking pulse-coherent acoustic Doppler profilers). These measurements will also be used to evaluate the dissipation of the tsunami in several different ways. To gage the degree of sediment reworking and redistribution under a tsunami, sediment samples will be analyzed using a digital-optical grain size analyzer. Data from this project will be archived and made available to the public through the NEES Project Warehouse/data repository (http://www.nees.org). The broader impacts of the proposed work address the present state of knowledge concerning the destructive nature of the tsunami and how effectively it is represented in laboratory studies. It is anticipated that the results of this work will affect present policies governing infrastructural health, emergency procedures and public safety in coastal areas potentially subject to tsunamis. A plan is also outlined concerning work with the NEES Large Wave Flume Facility's education and outreach personnel in aiding their established plans concerning public engagement and education regarding tsunamis and associated hazards, as well as their plans for encouraging careers in science and engineering. This will include live demonstrations of tsunami-sediment interaction in the Large Wave Flume Facility, during which the public will be able to witness the power of an onrushing tsunami. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).