AN EXPERIMENTAL STUDY ON THE TSUNAMI BOULDER MOVEMENT
ICCE 2014 Cover Image
PDF

Keywords

Tsunami boulder
Dam-break hydraulic experiment
Bore velocity
Boulder moving process
Boulder displacement
Boulder velocity

How to Cite

Liu, H., Sakashita, T., & Sato, S. (2014). AN EXPERIMENTAL STUDY ON THE TSUNAMI BOULDER MOVEMENT. Coastal Engineering Proceedings, 1(34), currents.16. https://doi.org/10.9753/icce.v34.currents.16

Abstract

A number of displaced tsunami boulders were observed through the subsequent in-site surveys after the 2011 Tohoku tsunami event. In this study, a series of dam-break type hydraulic experiments were carried out in an open channel with a concrete block setting on a horizontal bed just above the beach face to simulate the tsunami-induced boulder overland movement process. Three different initial water head settings were applied with three different tsunami- boulder interaction angles. Instantaneous water level and bore current velocity were measured, and the entire boulder moving process was recorded using a video camera. Sliding boulder movement was observed in the experiments. Comparing to the normal incident tsunami, oblique incoming tsunami wave resulted in a longer boulder displacement owing to the larger current-projected area. It was confirmed that the block dislodgement is not triggered immediately by the arriving of the water bore, but there exists a measurable time lag between the tsunami arrival and the inception of boulder movement. A small difference in the initial water head settings could lead to a significant difference on the total boulder displacement. As for the boulder moving process, three phases were identified from the experiment, i.e., the acceleration phase (at the beginning stage), the deceleration phase (in the middle stage), and the relatively steady moving phase (in the end). From the experiment, it was confirmed that the difference in the total boulder displacement is mainly ascribed to the boulder moving velocity difference during the deceleration and steady moving phases.
https://doi.org/10.9753/icce.v34.currents.16
PDF

References

Bryant, E.A., Young, R.W., Price, D.M., 1992. Evidence of tsunami sedimentation on the Southeastern Coast of Australia. Journal of Geology, 100, 753-765.

Costa, P.J.M., Andrade, C., Freitas, M.C., Oliveira, M.A., da Silva, C.M., Omira, R., Taborda, R., Baptista, M.A., Dawson, A.G., 2011. Boulder deposition Turing major tsunami events. Earth Surf. Process. Landforms, 36, 2054-2068.

Dawson, A.G., Shi, S., 2000. Tsunami deposits. Pure Appl. Geophys., 157, 875-897.

Etienne, S., Buckley, M., Paris, R., Nandasena, A.K., Clark, K., Strotz, L., Chagué-Goff, C., Goff, J., Richmond, B., 2011. The use of boulders for characterizing past tsunamis: Lessons from the 2004 Indian Ocean and 2009 South Pacific tsunamis. Earth-Science Reviews, 107, 76-90.

Frohlich, C., Hornbach, M.J., Taylor, F.W., Shen, C.-C., Moala A., Morton, A.E., Kruger, J., 2009.

Huge erratic boulders in Tonga deposited by a prehistoric tsunami. Geology, 37(2), 131-134.

Goff, J., Dudley, W.C., Maintenon, M.J., Cain, G., Coney, J.P., 2006. The largest local tsunami in 20th

century Hawaii. Marine Geology, 226, 65-79.

Goff, J., Weiss, R., Courtney, C., Dominey-Howes, D., 2010. Testing the hypothesis for tsunami

boulder deposition from suspension. Marine Geology, 277, 73-77.

Goto, K., Chavanich, S.A., Imamura, F., Kunthasap, P., Matsui, T., Minoura, K., Sugawara, D.,

Yanagisawa, H., 2007. Distribution, origin and transport process of boulders deposited by the 2004

Indian Ocean tsunami at Pakarang Cape, Thailand. Sedimentary Geology, 202, 821-837.

Goto, K., Okada, K., Imamura, F., 2010. Numerical analysis of boulder transport by the 2004 Indian

Ocean tsunami at Pakarang Cape, Thailand. Marine Geology, 268, 97-105.

Hall, A.M., Hansom, J.D., Williams, D.M., 2010. Wave-emplaced coarse debris and megaclasts in Ireland and Scotland: boulder transport in high-energy littoral environment: a discussion. Journal

of Geology, 118, 699-704.

Hearty, P.J., 1997. Boulder deposits from large waves during the last interglaciation on North Eleuthera

Island, Bahamas. Quaternary Research, 48, 326-338.

Holland, K.T., R.A. Holman, T.C. Lippmann, and J. Stanley. 1997. Practical use of video imagery in

nearshore oceanographic field studies. IEEE J. of Oceanic Eng., 22(1), 81-92.

Authors retain copyright and grant the Proceedings right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this Proceedings.