Collaborative Research: Long (Tsunami) Waves in Riverine Estuaries

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Physics of tsunami propagation through riverine environments is not understood well enough to quantify the hazard with reasonable confidence. Unanticipated tsunami behavior in rivers can be harmful to riverine ports, marinas, bridges, and other critical infrastructure. Tsunami penetration in rivers is largely determined by the interaction among the flow components of the tsunami, river, and tide as well as by river morphology. This project utilizes analytical, laboratory experimental and numerical modeling work, designed to reveal the conditions that determine tsunami intrusion and propagation in rivers. The findings would enable accurate predictions of riverine tsunami transformation that is directly beneficial for public safety and for reducing infrastructure damage in areas along rivers. The research program emphasizes education for undergraduate and graduate students entering the fields of physical oceanography, applied mathematics and engineering. Because of the topic's appeal, the project will be effective in promoting students to further advance their education and research, thereby potentially leading them to academic careers. The laboratory experiments will yield the time evolution of complex long-wave patterns which will be packaged into visual material that could be used in classrooms from high school to college graduate levels; the material will emphasize the tight linkage between mathematics and oceanography. In addition, outcomes from laboratory experiments will yield solid benchmark cases for the validation of numerical codes for simulating tsunamis in rivers suitable for benchmark testing within the research community. The research is designed to advance fundamentals in tsunami mechanics through the integration of theoretical approaches, numerical simulation, and laboratory experiments, all guided by field data analyses. It will bring insight into the mechanics associated with tsunami transition into a river, thereby leading us to identify which adjustments should be made to improve numerical representation of these critical tsunami processes. The specific questions to be addressed are: 1) how incident tsunamis transmit their energy through the river-mouth environment, 2) explaining why tsunami intrusion into a river results in a prolonged water accumulation, and 3) exploring interactions of tsunamis with river discharge. For analytical considerations, the large body of work from the tidal research community, will be utilized to determine which existing theoretical consideration for propagation of tides in rivers are applicable to tsunamis. Numerical simulations will be implemented for field-scale conditions, guided by 2011 Japan observations, to determine the physical parameters necessary to properly design the laboratory experiments. In addition, numerical experiments will be carried out in tandem with the controlled laboratory experiments to further explore the hydrodynamics associated with the tsunami transition from ocean to river. The laboratory research makes use of two different but complimentary experimental facilities: 1) a 2D flume designed to study the interaction between free surface waves, internal waves, and vertically sheared currents at the University of Southern California, and 2) a 3D wave basin designed for the high-precision study of nonlinear free surface wave transformation in the horizontal plane at Oregon State University.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.