ALBERT

Description: The countermeasures against storm surges and tsunamis in Japan are briefly reviewed covering roughly the last century. In spite of 22,000 deaths resulting from the Meiji Great Sanriku Tsunami just before the 20th century, neither central government nor local governments took effective countermeasures. The first positive countermeasures were taken by the central and local governments after the Showa Great Sanriku Tsunami and the Muroto Typhoon in early 1930s. The Seashore Act was enacted in 1956. After the 1959 Ise Bay Typhoon and the 1960 Chilean Tsunami, it has been the general practice to construct coastal dikes 5-6 m high as defense countermeasures. Tsunamis exceeding this height are met by combining structures, tsunami-resistant town development and defense systems. Quantitative tsunami forecasting announced by the Japan Meteorological Agency is currently state-of-the-art globally in terms of swiftness, preciseness and details.

Description: After the 1960 Great Chilean Tsunami, coastal dikes were remodeled and new ones constructed in Japan. In 1968, immediately after the completion of those construction and remodeling works, the Tokachi-Oki Earthquake struck, but fortunately the structures involved sustained very little damage. This led to a general feeling that it was possible to protect against the tsunamis completely by simply building coastal dikes and other defense structures. Japan did not see an increase in the number of tsunami researchers, but things were worse in the U.S. The National Science Foundation allocated its tsunami-related budget only to the NOAA, which issues tsunami forecasts, and allocated the rest of the budget entirely to ocean development. This situation continued until the 1983 Nihonkai-Chubu Earthquake Tsunami struck. In 1992, there was a tsunami earthquake off the coast of Nicaragua. Following that, research was conducted based on international cooperation through fax communications. Then cooperative international research continued to be done on tsunamis such as the 1992 Flores Tsunami, the 1993 Hokkaido Nansei-Oki Earthquake Tsunami, and the 1996 Irian Jaya Tsunami. However, their findings were provided only through Proceedings of the International Tsunami Symposium every two years, and most of the findings were limited to factual information about tsunamis. Requests for information on tsunamis rapidly increased after the 2004 Great Indian Ocean Tsunami, information not only on the tsunami itself but also on tsunami countermeasures. It was when JDR made its appearance. The JDR disseminated the latest information for practical use. It also benefitted those who were the sources of information, as they no longer had to deal with the frustration of having to wait for conferences held only every two years. In addition, the JDR reviews submissions much more quickly than do other journals. Tsunamis, such as the 2011 Great East Japan Earthquake Tsunami and the 2018 Sulawesi Earthquake Tsunami, continue to strike. As a platform for sharing knowledge related to reconstruction and countermeasures, as well as to tsunamis themselves, the importance the JDR is growing. This is why you are encouraged to contribute to the JDR.

Description: An unprecedented M9.0 earthquake occurring at 14:46 local time on March 11, 2011, off of northeast Japan’s Pacific Ocean generated a huge tsunami which had a run-up of over 40 m at the highest point and nearly 20,000 lives were lost. The tsunami demonstrated the need to drastically readdress current tsunami countermeasures. “Guidebook for Tsunami Preparedness in Local Hazard Mitigation Planning” published prior to the March 11 tsunami had already estimated, as one of the cases of tsunami assumptions, that the tsunami could be generated by the largest earthquake near off the Sanriku Coast predicted by the recent seismology. The seismotectonics had predicted that off the Sanriku Coast consisted of three independent blocks, which could conceivably cause an M8.6 earthquake at the largest. However, three blocks were not independent and they moved continuously to yield an earthquake of M9.0. The Guidebook had recommended a combination of three approaches for handling such a tsunami; Construction of defense structures, Tsunami-resilient town development, and Disaster prevention systems – defense structures were not expected to completely prevent every tsunami but only reduce its effect. Caissons forming part of Kamaishi Port’s tsunami breakwaters and registered in Guinness World Records, were overturned but reduced the tsunami height from 14 m outside the port to 8 m inside. Many coastal dikes were also destroyed, even though three surfaces – fore slope, top slope, and rear slope – had been protected using concrete and other means. Such phenomena pinpoint the importance of toe protection against erosion. Since 2004, tsunami inundation hazard maps have been distributed to communities in Japan as an aid to public education and as part of the country’s nationwide disaster prevention system. Unexpectedly, these maps had a negative effect in many places where residents living outside inundation areas mentioned on the hazard maps believed they were safe under all condition. Many did not in fact keep track of the actual tsunami rising in front of their very eyes and not evacuate, thus losing their lives. The tsunami hitting the coast of the Fukushima Prefecture had a run-up height almost double that designed in defense plans. The Fukushima No.1 Nuclear Power Plants of the Tokyo Electric Power Company (TEPCO) located on ground 4.8 m above sea level were immerged and a concurrent electric system failure led to total plant shutdown. The Fukushima nuclear disaster itself has become well known worldwide. The effects of the tsunami, however, are less so, despite damage such as fires, railroad destruction and drifting ships caused by the tsunami. With the nuclear incident overshadowing such effects, we are concerned that these results might be overlooked. To better prepare against potential future tsunami disasters, we must understand clearly what sort and how such diverse damage has been generated by the 2011 tsunami. This special issue focuses on the various types of tsunami-induced damages, emphasizing the valuable data and modeling obtained from field investigations in the tsunami-devastated areas. It will be more than worth publication if this special issue contributes in whatever way to furthering tsunami disaster research. Finally, we extend our sincere thanks to all of the contributors and reviewers involved with these articles. (written by Nobuo Shuto and Tomoyuki Takahashi)

Description: Examples of damages to coastal structures caused by tsunami-induced current are collected from documents in Japan, and classified into four types. Soil embankments near underpasses or bridge abutments are eroded by concentrating water current. Currents parallel to long structures can develop strongly enough to scour the structures toe and destroy them. Embankments made of soil are easily eroded by overflowing water of tsunamis. The toe of quay walls is unprotected against the waterfall that occurs when landed water returns and hits the nearly exposed sea bottom as tsunamis recede.

Description: There have been many studies on tsunami forces acting on structures, but few studies on tsunami-induced water flows that move a lot of sands or soils, resulting in damages to such structures as road embankments and seawalls. In the present study, the damage of soil embankments by tsunami overflow is discussed. Hydraulic experiments on movable beds reveal that the erosion of the downstream slope and the scouring at the rear toe are important factors in the erosion of soil embankments. An erosion rate law is experimentally established. Current velocity measured on a fixed bed verifies the application of the CADMAS-SURF to the present situation. A numerical method to simulate the erosion of soil embankments is developed using these data. It is applied to gain insight into the Shuto diagram (2001) about the damages of embankment obtained from field data for local tsunamis of short wave period in the past. Among six tests, reasonable agreements were obtained in four cases. In other two cases, the method gave the larger erosion than the expected ones from the diagram.

Description: The 2004 Indian Ocean Tsunami claimed more than 220,000 lives. It was a low-probability high-consequence event. A similar disaster could strike elsewhere, particularly in the Pacific but also in Caribbean, Atlantic, and Mediterranean regions. Unlike in seismic ground shaking, there is usually a short lead-time precedes tsunami attack: from a few minutes for a local source to several hours for a distant source. Because mega-tsunamis are rare and because forewarning of these events is possible, the primary mitigation tactic to date has been evacuation. Hence, most efforts have focused on the development of effective warning systems, inundation maps, and tsunami awareness. This strategy makes sense from the standpoint of saving human lives. However, it does not address the devastating damage to buildings and critical coastal infrastructure, such as major coastal bridges, oil and LNG storage facilities, power plants, and ports and harbors. Failure in critical infrastructure creates enormous economic setbacks and collateral damage. The accelerating construction of critical infrastructure in the coastal zone demands a better understanding of design methodology in building tsunamiresistant structures. In some coastal areas such as low-elevation coastal spits or plains, evacuating people to higher ground may be impractical because they have no time to reach safety. In these situations, the only feasible way to minimize human casualties is to evacuate people to the upper floors of tsunami-resistant buildings. Such buildings must be designed and constructed to survive strong seismic ground shaking and subsequent tsunami impacts. The primary causes of structural failure subject to tsunami attack can be categorized into three groups: 1) hydrodynamic force, 2) impact force by water-born objects, and 3) scour and foundation failure. Tsunami behaviors are quite distinct, however, from other coastal hazards such as storm waves; hence the effects cannot be inferred from common knowledge or intuition. Recent research has addressed tsunami forces acting on coastal structures to develop appropriate design guidelines, and mechanisms leading to tsunamigenerated scour and foundation failures. This special issue is a compilation of 14 papers addressing tsunami effects on buildings and infrastructure. The four main groupings begin with two papers on tsunami force acting on vertical walls. Arikawa experimentally investigates the structural performance of wooden and concrete walls using a large-scale laboratory tank in Japan. Also using a similar large-scale tsunami flume but in the US, Oshnack et al. study force reduction by small onshore seawalls in front of a vertical wall. The second grouping focuses on tsunami force on 3-D structures. Arnason et al. present a basic laboratory study on the hydrodynamics of bore impingement on a vertical column. Fujima et al. examine the two types of formulae for tsunami force evaluation: the one calculated from flow depth alone and the other based on the Euler number. Lukkunaprasit et al. demonstrate the validity of force computation recommended in a recently published design guideline (FEMA P646) by the US Federal Emergency Management Agency. The other two papers look into the specific types of structures: one is for light-frame wood buildings by van de Lindt et al, and the other is for oil storage tanks by Sakakiyama et al. The topic of debris impact force is the focus of the third grouping. Matsutomi summarizes his previous research on impact force by driftwoods, followed by the collision force of shipping containers by Yeom et al. Yim and Zhang numerically simulate tsunami impact on a vertical cylinder; this paper is included in this grouping because their numerical approach is similar to that of Yeom et al. As for the fourth grouping, Shuto presents field observations on foundation failures and scours, and Fujii et al. discuss the erosion processes of soil embankments. There are two more papers: those are the application of fragility analysis to tsunami damage assessment by Koshimura et al. and evaluation of an offshore cabled observatory by Matsumoto and Kaneda. The topics presented here are undoubtedly in progress, and many revisions and improvements are still needed in order to achieve better predictability for tsunami effects on buildings and infrastructure. We hope you find the papers in this issue intriguing and the information useful, and become further interested in this important natural hazard. Lastly, we wish to express our appreciation to the authors for their timely contributions, and to the reviewers for their diligent and time-consuming efforts.

Description: Natural disasters occur where natural phenomena and human society meet. Disaster impact differs in form and scale – even when the natural external forces are the same – depending on the way of society. Our knowledge of natural forces is also limited, making it much difficult to interpret disasters. In areas of frequent disasters, knowledge about highly vulnerable areas is passed as wisdom for the generations, and local residents know how to live safest. Living in disaster-prone areas puts residents at risk, but such areas often bring notable benefits to residents, so they have learned and devised wisdom to adapt to nature’s force. With disaster-resistant structures being more widely constructed and disaster experience decreasing, however, the local population has grown as new residents arrive, and local generational wisdom has often been lost. Simeulue Island, Indonesia, is a good example of how the transmission of local wisdom has minimized disaster damage. In the great 1907 tsunami, for example, several thousand of the island’s residents died and this experience of “a tsunami following an earthquake” has been handed down in lullabies, stories, and epics. Thanks to this wisdom, the death toll from the 2004 Indian Ocean Tsunami was just one out of a population of 78,000. This wisdom has been limited to this island geographically, however, rather than shared with neighboring islands. One basic principle for mitigating disaster damage is to share local wisdom world-wide – not limit it to local geographical areas. This requires stable nucleus to collect and disseminate such knowledge widely. The Journal of Disaster Research (JDR) has served this role for the last decade as it has grown. Human beings are forgetful creatures, so however much they may want to avoid major disasters after they happen – up to eight years or so, this wisdom rarely lasts longer than a decade. Fifteen years later, disasters are largely forgotten and preparation is no longer seen as urgent. How can we prevent this? It is my great hope that the JDR will continue to help prevent such oblivion and continue as a nucleus for disaster reduction in the decades ahead and further in the future. Nobuo Shuto May 22, 2015

Description: Immediately after World War II, economic and human losses due to water disasters were enormous in Japan. In the years of 1947 and 1953, for example, economic loss reach 10% of personal income, and the number of lives lost in the 1959 Isewan Typhoon exceeded 5,000. The Japanese government then implemented successive 5-year flood control plans that dramatically reduced such disasters. Economic loss by flooding now is on the order of 0.2% of personal income, and fewer than 100 lives are lost per year. The situation has begun changing in the last decade, however, ostensibly due to global warming and local climatic change such as the heat island phenomenon. The most typical change is the increase in heavy precipitation. Meteorologists sometimes call 1997 the turning point in climate change. The year 1998 was one of extreme heavy rain in Japan, with downpours exceeding 100 mm/h occurring 10 times and those of 50 mm/h almost 440 times. The record for 50 mm/h was broken in 2004, when some 470 such downpours occurred. Another marked change has been the increase in the fluctuation of precipitation, suggesting that drought may follow floods as a typical pattern portending major water disasters in the future. Lifestyle changes are another factor inducing water disaster. Increased urban populations inherently induce concentrated land use, paving of land surfaces, hazardous living conditions, etc. Frequent urban flooding and high underground use in Japan increases the danger for inundations. Wind disasters are also increasing. In September 2006, a tornado in Nobeoka, Kyushu, killed 3 people. In November 2006, another tornado struck Saroma, Hokkaido, killing 9 workers when a construction company's meeting room was destroyed. Polluted material transported long distances by wind is a big problem in Asia. Smoke from forest fires and chemical pollutants increasingly endanger people outside of the countries of origin, spreading throughout the continent and to islands beyond. This issue reviews recent meteorological and hydrographic disasters in urban areas that threaten to become major problems in the 21st Century.

Description: The Hokkaido Nansei-Oki Earthquake Tsunami that struck Okushiri Island off western Hokkaido, Japan's northeasternmost island in 1993 killed about 200 in Okushiri Town, which had a population of less than 4,000. Damage totaling over yen 66 billion was a severe blow to the community, which had an annual budget of only yen 5 billion. The tsunami was caught by the island and struck the Aonae district on the southern tip from both the west and east. Based on an experience from tsunami in 10 years earlier, it was thought that a tsunami would arrive more slowly than this one did, which increased the human toll. Fire caused by the tsunami increased losses. Among reconstruction efforts, remarkable are an artificial ground and cordial assistance based on monetary donation.