Tsunami Runup onto a Complex Three-dimensional Beach; Monai Valley
The Hokkaido-Nansei-Oki tsunami of 1993 that struck Okushiri Island, Japan, with extreme runup height of 30 m and currents of the order of 10-18 m/sec was a disaster, but provided fortuitous high-quality data. The extreme tsunami runup mark was discovered at the tip of a very narrow gulley within a small cove at Monai. High resolution seafloor bathymetry existed before the event and when coupled with bathymetric surveys following the event allowed meaningful identification of the seafloor deformation.
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A 1/400 laboratory model of Monai was constructed in a 205 m-long,
6 m-deep, and 3.5 m-wide tank at Central Research Institute for
Electric Power Industry (CRIEPI) in Abiko, Japan and partly shown in
Fig. 1. The laboratory setup closely resembles the
actual bathymetry. The incident wave from offshore, at the water
depth = 13.5 cm is known. There are reflective
vertical sidewalls at
and 3.5 m
(Fig. 2). The entire computational area
is 5.448 m
3.402 m, and the recommended time step and grid
sizes for numerical simulations are
= 1.4 cm and
= 0.05 sec.
The input wave is a LDN with a leading-depression height of 2.5 mm with a crest of 1.6 cm behind it
(Fig. 3). Waves were measured at
thirteen locations and complete time histories are given at three
locations, i.e.,
= (4.521, 1.196),
(4.521, 1.696), and (4.521, 2.196) in meters
(Fig. 4). These experiments were used in
the 2004 Catalina Island, Los Angeles, California NSF Long-Wave
Runup Models Workshop (Liu et al., 2008).
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References:
Liu, P.L.-F., H. Yeh, and C. Synolakis (2008): Advanced Numerical Models for Simulating Tsunami Waves and Runup. Advances in Coastal and Ocean Engineering, 10, 250 pp.