7.3 Nonstructural measures

the west coasts of Kyushu, we can imagine the propagation direction of

of the atmospheric-pressure waves is not clear.

Natural Hazards - Risk, Exposure, Response, and Resilience

routine work.

7.2 Structural measures

height are suitable.

gate between two jetties is effective.

at high risk of overflow.

104

atmospheric-pressure waves and predict the possible largest long-wave amplitude H in East China Sea, by applying the proposed Eq. (10). It is, however, difficult to place barometers at several islands, including uninhabited islands, far from the main island of Kyushu, and the maintenance of the barometers, with sustainable data transfer units, is a hard task. As long as we obtain time variation in atmospheric pressure only at one site, we can predict the possible largest amplitude H, by applying Eq. (10), although the accuracy of H is low, for the propagation direction

If fishing cooperatives and town offices obtain GPV atmospheric-pressure data, presented by JMA, to find out an atmospheric-pressure wave traveling east, they can predict the propagation direction, as well as the possible largest amplitude, of long-waves in East China Sea, where the accuracy of the predicted parameters is improved using Eqs. (8) and (9). It is important to catch every occurrence of large secondary undulation easily, even though both predictive accuracy and hitting ratio are relatively low. The fishing cooperatives and town offices, where the simple derivation process of Eqs. (8)–(10) is preferably understood, should be aware of the importance of the daily monitoring for variation in atmospheric pressure as a

The following structural measures against meteotsunamis are useful, depending

a. Breakwaters are raised for ports with experience of large harbor oscillation, where several dozen centimeters may be enough. In case high breakwaters work against the loading of fishes and cargos, lockages of less than 1 m in

b.The bay width is narrowed with jetties, to protect ports and towns at bay heads, without inconvenience for daily steerage. It should be noted that the flow velocity, due to not only meteotsunamis but also tides, between the jetties may be larger, resulting in seabed scour, and that wave energy may be trapped behind jetties, leading to water surface oscillation prolonged in the bay. Furthermore, some device is required to advance seawater exchange, for part of the bay is occlusive. If the district to be protected is a narrow area, a water

c. Permeable breakwaters with impounding reservoirs are constructed for coasts

located near a node of harbor oscillation, may be flown away owing to flow of large velocity. The fish that got away is always big. The right places should be determined considering both water level and flow velocity, based on the

e. Both drainage pipes and street gutters are designed to prevent inundation due to the intrusion of seawater into the residential area through the pipes and gutters. Although the walls of the castle, which is a world heritage, in Galle, Sri Lanka, rejected the tsunamis caused by the 2004 Indian Ocean earthquake, the seawater entered the inside of the walls through drainage pipes, leading to the flood.

d.Fishery facilities are built, or moved, to adequate places, for corves etc.,

characteristics of harbor oscillation in each bay or port.

on conditions including bay shape and water depth distribution:

The coastal structures are permitted to be built considering cost effectiveness, nearshore environment, etc., such that nonstructural measures, including evacuation and preparation against meteotsunamis, are necessary as follows:


Figure 37. A fishery boat hung by a mooring rope, as the water level lowers owing to meteotsunamis.

the narrowed area of the I-type harbor was located nearer to the harbor mouth, the amplification factor at the head for the first mode decreased, while that for the second mode increased. The C-type harbor showed the amplification depending on the position with the phase difference between the waves coming through two mouths. When the I-type harbor has the seabed crest, the amplification factor at the head for the first mode was larger than that for the second mode, while the reverse was true, when the I-type harbor has the seabed trough. Although the oscillation in Urauchi Bay had the second mode specific to T-type harbors, where antinodes appeared at their two harbor heads, future work is required to make clear the reason why the damping

Long-Wave Generation due to Atmospheric-Pressure Variation and Harbor Oscillation…

DOI: http://dx.doi.org/10.5772/intechopen.85483

Finally, the disaster measures were discussed against meteotsunamis, generated to propagate toward the west coasts of Kyushu. The methods of real-time prediction for meteotsunami generation were proposed using the inverse analysis, as well as

Sincere gratitude is extended to Satsumasendai City Office for providing the photographs shown as Figures 2 and 3. I also express my gratitude to Mr. Kosuke Fukita, Mr. Soichiro Hidaka, Mr. Taisuke Inoue, Mr. Hiroyuki Matsukawa, Mr. Shota Minami, Mr. Yuki Suetsugu, Mr. Taishi Toyofuku, and Dr. Kei Yamashita, who contributed to the numerical simulation, etc., when they were student members of our laboratory. I am grateful to the reviewer for suggestive comments on countermeasures against meteotsunamis. This work was supported by JSPS Grant-

processes were different between Urauchi Bay and the T-type harbor.

the simple prediction equations, after which both the structural and the nonstructural measures against meteotsunamis were summarized.

in-Aid for Scientific Research (C) Grant Number JP17K06585.

Division of Ocean and Civil Engineering, Graduate School of Science

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

and Engineering, Kagoshima University, Kagoshima, Japan

\*Address all correspondence to: taro@oce.kagoshima-u.ac.jp

provided the original work is properly cited.

Acknowledgements

Author details

Taro Kakinuma

107

#### Figure 38.

The waterproof walls equipped at Kinki Area Seaside Disaster Prevention Center in Osaka Prefecture, Japan. The wall panels can be carried and set at places where waterproof is supposed to be required. In case shown in the figure, the panels are piled up in front of the doors, using frames.

c. It is most important to notify inhabitants immediately that meteotsunamis are predicted to approach the coasts, using a community wireless system and speakers, or door-to-door visits. The prediction of disasters including meteotsunamis is probabilistic, commonly without high accuracy in their parameters, such that education to increase public awareness about disaster prevention is essential. It is crisis management that covers all the cases, whether the boy who cries wolf is right or not.
