The 2011 Great East Japan earthquake has shown all too clearly that disaster management and mitigation measures seen from the viewpoint of protecting society are not sufficient for addressing a national crisis such as the projected Nankai Trough earthquake or Tokyo inland earthquake whose damage is expected to exceed the present estimated damage. Our study explores the weakness against disasters in how modern Japanese society uses “reverse thinking” in which investigates studying how large-scale disasters may adversely affect society and increase damage effectively. This process profiles the worst disaster scenarios that could conceivably lead to a national crisis. Classifying these worst scenarios, we suggest policies to the problems that are common to many scenarios, and we present action plans for individual problems.

First, we conduct workshops for identifying damage magnification factors and evaluating their importance under the categories of human damage, property damage, and damage to social functions, unifying the awareness of research organization.

Second, we have researchers on 1) mortality, 2) tsunami inundation, 3) liquefaction, 4) capital function, 5) evacuation, 6) required assistance, 7) lifelines, 8) high buildings, 9) information networks, 10) government systems, and 11) economic systems analyze damage magnification conditions due to hazard, vulnerability and measure aspects.

Third, we sort potential final consequences and separate them based on commonality, and propose new policies and concrete action plans for preventing the occurrence of worst-case scenarios. This research is expected to give new paradigms in disaster management science and new ways of policy making and action planning that will minimize the undesirable consequences of catastrophic earthquake and tsunami and yield new knowledge on disaster processes and damage magnification scenarios.

Most importantly, we conclude that it is necessary to have a new Japanese governmental organization, such as a Ministry of Disaster Resilience or a Disaster Resilience Management Agency, handle these national crises.

It is extremely important to evaluate the extent of socioeconomic damage to draw up a disaster preparation program and determine the specifics and their scales when implementing disaster prevention and reduction measures before the occurrence of disasters. Yet, it has only been possible in the past to represent the entire damage costs by part of the damage that could be quantitatively evaluated. This necessarily resulted in underestimation. In this study, the author developed a method in which the descriptions of damage scenarios are collected from over a thousand people and the damage costs evaluated by examining the frequency of used words. Specifically, a questionnaire survey was first conducted to extract the people’s views of disaster, and the frequencies of specific words used in these descriptions of disaster were used as indicators of damage. It was then assumed that the difference in the appearance of these words in newspaper articles before and after an actual disaster represents the damage impact, and this difference was used to estimate the damage costs. The results suggested the possibility of developing an evaluation method based on collective intelligence, as well as the need to improve and refine the method in the future.

We have reviewed liquefaction-induced damage to reclaimed ground, levees and industrial complexes, caused by the 2011 off the Pacific Coast of Tohoku Earthquake. Then, we reconsidered the method of the prediction of liquefaction and estimated liquefaction at Urayasu housing area using a new liquefaction prediction method based on dynamic numerical liquefaction analysis of the ground. We also clarified the feature of the damage of levee due to the 2011 Great Tohoku Earthquake based on the dynamic liquefaction analysis and listed the lessons taught by the analyses and the damages due to the 2011 Tohoku Great Earthquake are shown.

Many people died in the Great East Japan Earthquake. However, children in Kamaishi City survived by taking advantage of what they learned from disaster prevention education. It was called the “Kamaishi Miracle,” and the story spread around the world. In this study, the disaster prevention education that made possible the appropriate evacuation of the children is examined and future education possibilities are discussed. First, it should be pointed out that most disaster prevention education conducted before the earthquake took the form of “threatening disaster prevention education” or “knowledge-oriented disaster prevention education.” To solve the deficiencies in these programs, “attitude-oriented disaster prevention education” with a focus on children’s independence is proposed. In addition, three educational guidelines regarding evacuation from tsunamis are discussed. We also study the current status of disaster prevention education in Japan after the earthquake and show that when it puts an emphasis on life and community it have far-reaching effect.

Characteristics of long-period seismic ground motion and response of tall buildings are investigated in this paper to promote earthquake proof countermeasures considering the damage caused by the 2011 Tohoku earthquake. 3D finite difference method and the reciprocal theorem are used to examine the effect of sedimentary basin structures on seismic wave amplification. Natural period and damping of tall buildings are evaluated by ambient vibration tests and earthquake response observation during construction or demolition of the buildings. The effects of dynamic soil-structure interaction on response amplification of tall buildings are confirmed applying wave propagation theory to a continuum building model. Finally, a newly built base-isolated building with an isolated rooftop laboratory is introduced for full-scale long-period shaking experiment by installing actuators and jacks. Experience of long-period shaking in the building is also available with virtual reality view of indoor damage, which is effective for promotion of seismic countermeasures such as fixing furniture and safe evacuation.

This study proposes elements for creating scenarios covering those needing support during a natural disaster, comprising: 1) coefficients for scenarios concerning those needing support during a disaster, and 2) quantitative damage estimation cases related to facilities for those needing support during a disaster. These elements have not been incorporated into conventional damage estimation. The scenarios were applied to Tokyo, which is assumed to be an area affected by earthquakes occurring directly beneath the Tokyo Metropolitan Area, to establish a support system and implement map training.

It is important to extract, clarify, and share the lessons learned from disasters to enhance preparedness for and effective responses in a disaster. This paper aims to describe the development of a web database system to share lessons learned by disaster science experts based on experiences of the 2011 Great East Japan Earthquake Disaster. First, an interview survey was conducted with local government officers in areas identified as being at risk during the Nankai Trough Earthquake to identify their needs. Next, we reported on the use of the system for three months after its release based on analyses of access log data.

The role of recovery organization management is important, and organizations in various forms have been established internationally to aid recovery from large-scale disasters. This paper clarifies three types of recovery organizations by analyzing them in various countries based on disaster organization theory. Furthermore, it analyzes recovery organizations that operated after the Hanshin-Awaji Earthquake and the Great East Japan Earthquake in Japan. It then examines the operations of recovery organizations during large-scale earthquakes that may lead to a national crisis by comparing recovery organizations internationally. Finally, this paper clarifies the necessity of “emergent” organizations.

The Great East Japan Earthquake occurred on March 11, 2011. Tohoku region, off the coast of the Pacific Ocean, was severely damaged by the tsunami, and all of Japan was affected. Recently, torrential and guerrilla rains have been frequently occurring in Uji, Kyoto, which suffered massive damage on August 13, 2013. Soma, Fukushima, and Uji made tremendous efforts for supporting victims’ recovery by using spatial information and GIS. These successful efforts indicate that they had been using spatial information efficiently in their daily operations.

This paper describes the learnings from the past efforts in disaster affected areas and discusses how these areas had been using spatial information for efficient daily operations. The paper makes suggestions to build a GIS-based information system with seamless interaction between daily operations and disaster management, and introduces new challenges faced by Kitakyushu, Fukuoka using spatial information based on cloud computing network for regional disaster resilient societies.

In the last two decades, three great earthquakes have occurred in Japan: the Hanshin-Awaji earthquake of 1995, the Mid-Niigata earthquake of 2004, and the East Japan Earthquake of 2011. After the East Japan earthquake, a devastating tsunami caused significant casualties and home destruction. More than 18,500 people were killed and more than 121,000 homes were destroyed. In addition, the tsunami destroyed nuclear power stations, which resulted in a severe crisis not previously experienced in Japan.

On the other hand, earthquake disasters on a huge scale have been announced to occur as probability of about 70% in the next three decades. One such earthquake is Tokyo inland earthquake that destroys 610,000 homes and kills 23,000 people, and the other is the Nankai Trough earthquake that destroys 2,380,000 homes and kills 320,000 people. In addition, compound disasters where one disaster merges with another disaster may cause damage on a mega scale in this century.

In order to address these mega disasters, it is very important to make efforts to reduce damage in the pre-disaster period. According to local plans for national resilience, each municipality must make efforts to reduce level of damage which is able to response trough a Business Continuity Plan (BCP). In addition, each municipality must implement long-term urban projects with a vision toward reconstruction after a mega disaster trough a pre-disaster recovery and reconstruction plan. It is necessary to make revolutionary efforts rather than standard disaster management efforts to reduce damages in the pre-disaster period.

The Emergency Job Creation (EJC) program in which unemployed people are hired for recovery works funded by the government was introduced after the 2011 earthquake and tsunami disaster in Japan. The program is very similar to Cash for Work (CFW) programs that are often implemented as social safety nets (SSNs). This paper evaluates how the EJC program targeted those most in need. From four projects, 938 participants were sampled and simple selection bias tests were conducted among job applicants in the region where the project was undertaken. Participants of the EJC program included more single females and irregular workers than the population group, thus demonstrating the EJC’s self-targeting function. Around 80% of participants were without dependent family members implying that there are two types of potential participants: those who prefer limited responsibilities with relatively low wages, and those who prefer a larger burden of responsibility with relatively higher wages. Because the wages provided by the EJC program may be high enough for the former, but too low for the latter, the program eventually excluded the second group. Similar programs in future should provide other types of jobs corresponding to people’s preferences. Previously unemployed participants were likely to be those who lost their houses; that damage had pushed them into the labor market. Because of the relatively minor existing SSN for housing damage, the EJC program served as an important safety net for disaster-affected people without a private safety net such as insurance.

An earthquake in metropolitan Tokyo would be a national crisis in terms of the enormous number of affected population and properties and various types of complicated damages and impact in areas where there is a concentration of capital, social, and economic functions. Moreover, the process of being affected by the disaster is so complicated that it has not been fully understood and the various possibilities of earthquake occurrence scenarios have not been fully analyzed. In addition, those understandings and analyses have not been fully utilized for disaster mitigation or preparedness.

Intended to estimate complicated phenomena, this study discusses a method to analyze various phenomena by breaking down a method for estimation component pieces, making each piece work as a web service, and getting them to cooperate with one another as necessary. We also develop an earthquake-disaster estimation web application that can analyze seismic intensity, exposed population, lifelines, business establishments, goods supply and demand, and so on.

Using an exposed population, the period of business disruption at business establishments, the supply and demand balance of necessities, and an amount of exposure of administrative functions as impact indices, we use our method to analyze the change in impact indices at many epicenters exhaustively plotted in the metropolitan Tokyo area. As a result, the scenario of an earthquake with a great impact is quantified in light of the earthquake susceptibility of the ground, distribution of population, business establishments, administrative functions, and so on.

The South China Sea Tsunami Workshop (SCSTW), initiated in 2007 by internationally recognized tsunami expert Prof. Philip L.-F. Liu at Cornell University, has been conducted eight times in the Asia-Pacific region. The SCSTW’s objective is to set up an international academic platform through which strong interactions and collaborations can be established among coastal physical oceanographers, geophysicists and engineers from the South China Sea region can meet and address tsunami generation mechanisms, propagation characteristics and the corresponding coastal effects. This workshop supports approaches to tsunami disaster protection and hazard mitigation. The 8^th South China Sea Tsunami Workshop (SCSTW-8), held in Changsha, China, from Nov. 9 to 13, 2015, was hosted by the Changsha University of Science and Technology.

Typhoon-induced storm surges and significant waves are predominant coastal disaster features of China’s east coast. One example is the latest Typhoon Meranti in Sept. 2016, which significantly damaged the infrastructure and resulted in the loss of dozens of lives in China’s coastal regions, especially in Fujian province. The study of typhoon-induced storm surges is thus highly important in coastal disaster prevention and mitigation.

This special issue consists of 7 papers focusing on the recent research progress in tsunami and storm surge presented in the SCSTW-8. Results are analyzed and discussed using different research approaches, including laboratory experiments, analytical analysis, data assessment and numerical simulation. As the editor of this special issue, I would like to express my sincere appreciation to the authors for their invaluable contributions and to the reviewers for their insightful comments and suggestions. Special thanks go to Dr. Yu Yao of the Changsha University of Science and Technology for his generous assistance in preparing this special issue. I hope readers will find the papers in this special collection both interesting and useful.

The vulnerability of low-lying reef-fringed atolls to coastal inundation in extreme wave events is of increasing concern in the context of global sea level rise. Wave-induced setup is an important component of wave runup along reef shorelines. We improved a semi-analytical model to investigate wave-induced setup over fringing reefs crested by a shallow reef. Using mass balance and hydraulics, we developed the model based on flow around reef crest kinematics. We proposed a scaling factor to account for flow unsteadiness and reef-crest shape effects. Our solution showed that wave setup on the reef flat is a function of both offshore wave steepness and the wave refection coefficient. Validation of the model by laboratory data shows that the model reproduces the maximum wave-induced setup on the reef flat in the presence of a reef crest with diffident crest widths. Applying the model to experimental data under various reef configurations and wave conditions were also successful. We found that the scaling factor in the model increased with increasing fore-reef slope but was insensitive to variations in reef-crest width. A key requirement for the model to do is that the reef-crest submergence must be small enough or nearly emergent so that an approximate critical flow condition exists.

The non-hydrostatic depth-integrated model we developed to study solitary waves passing undisturbed in shape through a porous structure, involves hydrodynamic pressure. The equations are nonlinear, diffusive, and weakly dispersive wave equation for describing solitary wave propagation in a porous medium. We solve the equation numerically using a staggered finite volume with a predictor-corrector method. To demonstrate our non-hydrostatic scheme’s performance, we implement our scheme for simulating solitary waves over a flat bottom in a free region to examine the balance between dispersion and nonlinearity. Our computed waves travel undisturbed in shape as expected. Furthermore, the numerical scheme is used to simulate the solitary waves pass through a porous structure. Results agree well with results of a central finite difference method in space and a fourth-order Runge-Kutta integration technique in time for the Boussinesq model. When we quantitatively compare the wave amplitude reduction from our numerical results to experimental data, we find satisfactory agreement for the wave transmission coefficient.

To study wave effects on storm surge, a depth-averaged 2D numerical model based on the Delft3D-FLOW model was utilized to simulate near-shore hydrodynamic responses to Typhoon Khanun. The Delft3D-WAVE model is coupled dynamically with the FLOW model and the enhanced vertical mixing, mass flux and wave set-up were considered as wave-current interaction in the coupled model. After verifying storm surge wind and pressure formulae of storm surge and optimizing calibration parameters, three numerical tests with different control variables were conducted. Model tests show that wave effects must be considered in numerical simulation. Simulating the flow-wave coupled model showed that wave-induced surge height could be as large as 0.4 m in near-shore areas for Typhoon Khanun. Comparing to its contribution to the peak surge height, wave-induced surge plays a more significant role to total surge height with respect to the time-averaged surge height in storm events. Wave-induced surge (wave setup) is in advance of typhoon propagation and becomes significant even before the typhoon landfall. Model tests demonstrate that the wave effects are driven predominantly by the storm wave, while the boundary wave contribution is rather limited.

Beach erosion caused by extreme wave events (storm surges) is reported to occur in many coastal areas. Artificially lowering the groundwater table effectively stabilizes sand beaches in an environmentally friendly way. Mechanisms affecting beach stabilization remain unclear, however, due to the complex interaction between waves and coastal seepage. This study discusses the effects of coastal seepage on beach profile evolution and bed materials sorting based on laboratory experiments in which seepage is induced artificially by a drain pipe at three cross-shore locations on a 1:10 beach. Morphodynamic beach responses with and without seepage under a typical cnoidal wave condition are reported. Results show that artificial seepage impacts only insignificantly on total upper-beach deposition volume but could increase accretion on the berm’s leeside by reducing seaside sand accumulation. It also induces a steeper berm slope and shoreline recession. A drain pipe near the shoreline generated the greatest accretion height on the upper beach. Seepage location had no significance effect on bed material sorting, however.

A series of experiments conducted to study fluid mud movement in currents with a fluctuating water surface involved measuring fluid mud yield stress, bed shear stress, and water surface fluctuation. To observe fluid mud movement, we dyed a sheet of fluid mud in the water flume cross-section red. We then calculated the fluid mud transportation velocity based on mud sheet displacement over time. Experiments showed that water surface fluctuation plays an important role in fluid mud movement. Under conditions of water surface fluctuation, we were able to observe fluid mud oscillation in the case that the interface of the water and fluid mud is clear. After several oscillation cycles, fluid mud is transported downstream by water currents.

Wave deformation on a sloping seabed and the incident angle of waves greatly influence local submarine pipeline scour. Most previous studies on such scour considered wave deformation but not incident wave angle. Using regular waves with an incident angle of 45°, we investigated 3D scour around an embedded submarine pipeline under oblique waves in experiments. After examining wave deformation near the pipeline at different embedment depths, we analyzed how seabed scour evolved around the pipeline. Results of experiments showed that under oblique wave action, pipeline embedment depth affected wave height on both seaside and leeside of the pipeline. A 3D scour hole occurred under the pileline when the ratio of embedment depth to pipe diameter (e/D) was less than 1/4. Different forms of sand ripples also occurred on both sides as e/D changed. The embedment depth also determined the rate at which scour developed. The scour hole evolved in two distinct stages: rapid and slack. The scouring rate on the right side of the pipeline was greater than that on the left during the rapid phase, leading to an imbalance in scouring depth between the two sides.

Lingding Bay in the Pearl River Estuary, located on the north coast of the South China Sea, experiences frequent storm surges caused by typhoons. The geomorphic features of the Pearl River Estuary have changed tremendously due to natural processes and human activities over the last century, and these changes have led to changes in the hydrodynamic environment, such as a reduced capacity for holding tides in the coastal zone. In this paper, the relation between geomorphic features and the capacity for holding tides is analyzed. In order to ascertain how historical landform change affects this capacity, we study the spatial morphology change of Lingding Bay in the Pearl River Estuary (since 1906) through the analysis of historical topographic maps and nautical charts. The shape index and fractal dimension were introduced as indicators to reflect coastline changes that have affected the tides. The tidal dissipation rate and tidal influx were found to describe a bay’s capacity to hold tides. The results show that, since 1906, the tidal influx and the tidal dissipation rate have decreased by about 14.11% and 23%, respectively, in the study area. We suppose that these changes could be attributed to geomorphic changes, primarily changes brought about by land reclamation projects.

On 9–10 September 2015, the East Kanto region of Japan experienced a period of record-breaking heavy rainfall that caused a number of fatalities and serious property damage. The maximum 24-hr rainfall total (0600 UTC 9 September 2015 to 0600 UTC 10 September 2015), about 500 mm, was recorded over Tochigi Prefecture. Spatial and temporal variations in the meteorological and hydrological characteristics of this rainfall event were analyzed using data from the Japan Meteorological Agency’s (JMA) C-band radar network and data from the X-band polarimetric radar network (XRAIN). The rain gauge data available from the Kanto region has a temporal resolution of 10 min. The spatial and temporal resolutions of the JMA C-band radar data are 1000 m and 5 min, respectively, whereas the XRAIN radar has spatial and temporal resolutions of 250 m and 1 min, respectively. Data from the two radar networks were compared, both with each other and with data from various rain gauge networks to validate their accuracy. The 24-hr total rainfall data from both radar networks showed frequency distributions similar to those showed by the rain gauge data. However, the JMA and XRAIN data showed different distributions for the higher rainfall intensity thresholds. There was no relationship evident between rainfall and elevation in either of the radar datasets recorded during this event. The spatial distribution of rainfall over the study area derived from XRAIN showed clear variations, whereas the JMA radar did not. This is most probably related to the coarser spatial and temporal resolutions of the JMA observations. Based on a comparison of data from the rain gauge and radar networks, the XRAIN data more accurately reflected the rain gauge stations than did the JMA data. From a hydrological perspective, the Kinugawa watershed is unique in terms of its topography. The upper part of the watershed is wide and mountainous, whereas the rest is narrow and elongate north–south. The rain echo moved from south to north over the catchment, and the highest 24-hr accumulated rainfall totals were recorded mostly in the upper (northern) part of the Kinugawa watershed, whereas there was less rainfall in the lower (southern) part. This pattern suggests a high probability of serious flooding along the Kinugawa River in the days following such a rainfall event if the heaviest rainfall moves northwards over the watershed.