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A field survey team went to Palu City, Indonesia in the aftermath of the September 28th, 2018 earthquake and tsunami to investigate its effects on local infrastructure and buildings. The study focused on the coast of Palu Bay, where a tsunami wave between approximately 2 and 7 m high impacted the local community as a result of several complex tsunami source mechanisms. The following study outlines the results, focused on loading caused by debris entrained within the inundating flow. Damage to timber buildings along the coast was widespread, though reinforced concrete structures for the most part survived, providing valuable insights into the type of debris loads and their effects on structures. The results of this survey are placed within the context of Canadian tsunami engineering challenges and are compared to the recently-released ASCE 7 Chapter 6 – Tsunami Loads and Effects, detailing potential research gaps and needs.

Five cases of ports in Japan and Indonesia that have subsided by a metre or more were analysed. The findings suggest that there are no unsurmountable technological, cost-benefit, financial and soci...

In the past two decades there have been fears that many low-lying atoll islands around the world could disappear as a consequence of climate change and sea level rise, leading to mass migration and threatening the existence of several island nations. Here we show how sea level rise does not inevitably lead to coastal areas becoming uninhabitable, and that humans have an innate and often underestimated capacity to adapt to changes in their environment. To do so we showcase three instances of human- and earthquake-induced land subsidence that have taken place in the 21st century, where the coastal/island areas are still inhabited despite the challenge of living with higher water levels: the Tohoku coastline following the 2011 Tohoku Earthquake Tsunami (subsidence ∼0.4–1.0 m), the present day situation of coastal areas in Jakarta due to ground water extraction (>5.0 m), and the islands of Tubigon, Bohol in central Philippines after the 2013 Bohol Earthquake (∼1.0 m). Humans are able to adapt and arrive at solutions even when confronted with cases of rapid rises in water levels, and thus it is likely that in the future vulnerable coastlines will be engineered and largely remain at present day locations, particularly in densely populated areas. If anything, around densely populated areas it is more likely that humans will continue to encroach on the sea rather than the reverse. We caution, however, that small islands are not homogeneous, and many are unlikely to respond to rising sea levels in the manner that atolls do (in fact, many might just resort to build at higher elevations). Where engineering and other adaptation responses become necessary, the financial and human resource requirements may well be beyond capacity of some small islands, which could lead to impoverishment and associated challenges in many communities.

The September 28, 2018 earthquake and tsunami, which occurred north of Palu City, Indonesia, attracted widespread interest from the scientific community due to the unusually large tsunami ...

In the case of a near-field tsunami event, coastal residents must quickly become aware of the potential danger of a tsunami taking place and start taking actions to evacuate. The present pa...

In 2018, Lombok island, Indonesia, was hit by a series of destructive earthquakes that caused thousands of casualties and widespread material damage. In response to those events, a field survey was conducted along the coast of Lombok aiming at collecting data about disaster preparedness and awareness of local inhabitants regarding natural disasters, with a focus on tsunami events. During the survey, the authors interviewed witnesses of small tsunami waves that were generated by the 2018 earthquakes. The work described here encompasses the authors’ field observations, which helped ascertain the occurrence of small-scale tsunamis, and the analysis of data collected via unstructured interviews and a limited questionnaire survey. Attention is drawn to the potential value added by recording small-scale tsunamis for future research, and some insights into what priorities should be set for future disaster risk management in Lombok are provided. The authors suggest that improvements in disaster awareness and education of residents, flood-proofing of houses that are bound to be reconstructed after the earthquakes, and investment in a fully modern flood warning system would be beneficial.

Land subsidence has triggered severe coastal floods in Jakarta, whose mechanism has been extensively investigated by researchers and engineers. The government has also recognized this fact, which has partially contributed to the recent announcement that the capital will be relocated to East Kalimantan. However, it is not clear whether ordinary people perceive the progress of land subsidence as their own issue. To ascertain this, a field survey was conducted after a major coastal flood that took place in December 2017, which revealed that nearly half of the people living in a rapidly sinking coastal community were not aware of the ongoing land subsidence under their own houses. Severe flood and land subsidence were not strongly recognized as interlinked problems by local citizens. Rain-induced flooding is common in the community, and this may explain why a quarter of respondents did not fear the 2017 coastal flood, despite their houses being flooded, in some cases to a depth above their heads. Land subsidence has an adverse effect on flooding. Awareness building programs for normal citizens should be promoted, in order to articulate the significance of stopping groundwater extraction for mitigating land subsidence and the flooding it induces.

Sea level rise will pose a significant challenge to coastal settlements throughout the planet and is likely to disproportionately affect poorer communities, which are usually located in particularly vulnerable areas. Coastal areas in Jakarta have been experiencing rapid subsidence in recent years, and could serve to illustrate the likely challenges that future sea level rise could have on such communities. To ascertain the level of awareness about the threats facing them questionnaire surveys were conducted amongst one relatively poor community that is situated below sea level, protected from the sea by a thin concrete dyke. The results show that while local inhabitants appear to be aware about the hazards they face, many seem to underestimate their severity, possibly due to a high frequency of exposure in the recent past. The situation in the area appears to be worsening with each passing year, and it is imperative that remedial actions to halt ground subsidence are carried out and/or important remedial actions to adapt to the ground subsidence are implemented. Failure to do so could eventually result in a significant loss of life in the area.

The September 28 2018 Palu tsunami surprised the scientific community, as neither the earthquake magnitude nor its strike-slip mechanism were deemed capable of producing the wave heights that were observed. However, recent research has shown that the earthquake generated several landslides inside Palu bay. The authors conducted a post-disaster field survey of the area affected to collect spatial data on tsunami inundation heights, nearshore and bay bathymetry, and carried out eyewitness interviews to collect testimonies of the event. In addition, numerical simulations of the tsunami generation and propagation mechanisms were carried out and validated with the inferred time series. Seven small submarine landslides were identified along the western shore of the bay, and one large one was reported on the eastern shore of Palu City. Most of these landslides occurred at river mouths and reclamation areas, where soft submarine sediments had accumulated. The numerical simulations support a scenario in which the tsunami waves that arrived at Palu city 4–10 min after the earthquake were caused by the co-seismic seafloor deformation, possibly coupled with secondary waves generated from several submarine landslides. These findings suggest that more comprehensive methodologies and tools need to be used when assessing probabilistic tsunami hazards in narrow bays.

The authors conducted extensive field surveys in densely populated coastal areas affected by land subsidence in Indonesia, Philippines and Japan. The results indicate that the preferred adaptation mechanism for coastal areas is elevating them using soil, rubble, or coral stones, and then re-surfacing to obtain a smooth surface, and building dykes where possible. Eventually, pumps are installed, and new areas can be reclaimed from the sea. By studying how densely populated coastal communities have attempted to adapt to land subsidence, it is possible to try to understand the effects that future sea level rise will have on other areas of the planet.

The present work projects the extent of coastal floods by the year 2050 in Jakarta, one of the fastest growing megacities in the world, using a coastal hydrodynamic model that considers abnormal high tides, sea-level rise, and land subsidence. The tidal constituents were adjusted in a manner to reproduce the observed tidal record during the extensive coastal floods that took place on November 2007, when it is likely that a La Niña event, the 18.6 year lunar nodal high-tide cycle, and other abnormal tide mechanisms took place simultaneously. The simulations demonstrate that by the middle of this century extensive floods could potentially reach several kilometers inland in Jakarta. Land subsidence is clearly one of the major challenges facing the city, as considering only the influence of sea-level rise indicates that such floods may be limited to within a few hundred meters of the coastline. From 2000 to 2050 the potential flood extent is estimated to increase by 110.5 km2. Land subsidence is responsible for 88% of this increase. The results also indicate that the rate of flood area expansion in the 2025–2050 period would be 3.4 times faster than during the 2000–2025 period, demonstrating a non-linear increase in flood risk with the passage of time. Keywords Jakarta; Coastal flood; Land subsidence; Sea-level rise; Oceanic tide; Urbanization; Abnormal high tides; ENSO; 18.6-year lunar nodal cycle Highlights •Future coastal flooding in Jakarta was projected through a coastal hydrodynamic model. •The model took into account land subsidence, SLR, and abnormal high tide. •From 2000 to 2050 the potential flood extent is estimated to increase by 110.5 km2. •Land subsidence is responsible for 88% of this increase. •The extent of flood areas will exponentially increase with the passage of time.

Sea level rise and an increase in typhoon intensity are two of the expected consequences from future climate change. In the present work, a methodology to change the intensity of tropical cyclones in Japan was developed, which can be used to assess the inundation risk to different areas of the country. As a result, the probability of a storm with an equivalent return period in the year 2100 to that of the worst storm in the 20th century overcoming sea defences around Tokyo Bay could be calculated. The risk of higher storm surges, coupled with different sea-level-rise scenarios, highlights how the dykes around Tokyo or Kawasaki could fail unless adaptation measures against climate change are attempted. The cost of adapting to both of these effects by building higher coastal dykes and raising port areas outside them was quantified. Finally, an estimation of the cost of allowing the areas behind the defences to be flooded was also made, clearly showing that the cost of adaptation measures is clearly lower than the cost of inaction. Keywords Storm surge – Sustainability of coastal defences – Sea level rise – Typhoons

Category 5 Typhoon Haiyan (known as Yolanda in the Philippines) made landfall in the Philippines on the 8 th November 2013 at almost the peak of its power, devastating the islands of Leyte and Samar, amongst other places. The present paper analyses the degree of awareness and preparedness of the islands of Samar and Leyte in the Philippines against storm surges prior to the arrival of typhoon Haiyan. The analysis was based on field surveys and interviewed with a variety of local residents and officials conducted during field surveys in the months after the event. One of the key problems identified during the interviews was how people were not able to clearly conceptualize the concept of storm surge. Despite receiving storm surge warnings it appears that many residents and local authorities “under-estimated” the event and thought that they could evacuate at a later stage or during the storm itself. The results clearly highlight the need for better education and for development strategies in the region to focus on improving the resilience of local inhabitants.

The authors have examined the characteristics of Typhoon Haiyan (Yolanda), which made landfall on the coast of the Philippines on November 2013, generating a substantial storm surge. In order to better understand the storm surge phenomenon, its nature and severity were analysed by means of a numerical simulation and a field survey. Unlike most other tropical cyclones that weaken before they hit land, Haiyan struck Leyte Island at near peak strength, with maximum sustained wind speeds of 160 knots, the strongest in the recorded history of the Western North Pacific. Haiyan approached very quickly with a forward speed of 41 km/h towards Leyte, which was also the fastest among typhoons with similar intensities. As a result of these extreme gusts and the exceptionally low central pressure of the typhoon (895 hPa), Haiyan caused the largest storm surge in the recorded history of the Philippines. Numerical simulations show that the maximum storm surges occurred in Leyte Island and Samar Island. A storm surge field survey conducted by the authors corroborated this, with maximum inundation height of 7 m recorded in Tacloban, located at the northern end of Leyte Gulf. The simulation results also corroborate the fact that water levels at some locations first lowered and then rapidly began to increase after an hour.

The Japanese coastal areas have a lot of different types of coastal structures with different purposes, and it is important to understand each structure's effects on tsunami. In the present paper, the authors focused on detached breakwaters effects on tsunami flow around coastal dykes with a field data investigation and laboratory experiments using a tsunami basin. The field data obtained from the 2011 Tohoku Earthquake and Tsunami showed that tsunami flow was not uniform along a coastal dyke with the specific arrangement of detached breakwaters. The laboratory experiments performed in a tsunami basin showed that a detached breakwater with a small detached breakwater parameter (distance from the shoreline/length of the opening)had a tsunami mitigation effect along the shoreline just behind the main body of the breakwater, but did not have a tsunami mitigation effect along the shoreline just behind the opening. The results obtained from the laboratory experiments agreed with the field data of the 2011 tsunami.

This study presents the results of an experimental research program dealing with spatial debris motion on a horizontal apron depicting a typical harbor wharf. Accordingly, scaled-down 6.1-m (20-ft) shipping containers were equipped with a novel yet nonintrusive real-time tracking system and motion sensors. The instrumentation allowed for the spatiotemporal tracking of debris specimens moving across the apron while entrained by an incoming tsunami-like broken bore. The system proved its capabilities and accuracy; this was particularly challenging since this was the first time the system was used in water. The experiments involved using various numbers of shipping containers that were either arranged in one layer or stacked in two layers. In addition, the effect of different numbers of container rows was also investigated to study the influence of the overall container count and placement with respect to their longitudinal displacement and dispersion (spreading) across the apron. Linear relationshi...

The design of breakwater armour units against tsunami attacks has received little attention in the past because of the comparative low frequency of these events and the rarity of structures designed specifically to withstand them. However, field surveys of recent events, such as the 2011 Great Eastern Japan Earthquake Tsunami and the 2004 Indian Ocean Tsunami, have shown flaws in the design of protection structures. During these extreme events, many breakwaters suffered partial or catastrophic damage. Although it is to be expected that most normal structures fail due to such high order events, practicing engineers need to possess tools to design certain important breakwaters that should not fail even during level 2 events. Research into the design of critical structures that only partially fail (i.e., “resilient” or “tenacious” structures) during a very extreme level 2 tsunami event should be prioritized in the future, and in this sense the present paper proposes a formula that allows the estimation of armour unit damage depending on the tsunami wave height.

On October 25, 2010, a large earthquake occurred off the coast of the Mentawai islands in Indonesia, generating a tsunami that caused damage to the coastal area of North Pagai, South Pagai, and Sipora islands. Field surveys were conducted soon after the event by several international survey teams, including the authors’. These surveys clarified the tsunami height distribution, the damage that took place, and residents’ awareness of tsunamis in the affected islands. Heights of over 5 m were recorded on the coastal area of the Indian Ocean side of North and South Pagai islands and the south part of Sipora island. In some villages, it was difficult to evacuate immediately after the earthquake because of the lack of routes to higher ground or the presence of rivers. Residents in some villages had taken part in tsunami drills or education; however, not all villages shared awareness of tsunami threats. In the present paper, based on the results of these field surveys, the vulnerability of these islands with regards to future tsunami threats was analyzed. Three important aspects of this tsunami disaster, namely the geographic disadvantage of the islands, the resilience of buildings and other infrastructure, and people’s awareness of tsunamis, are discussed in detail, and corresponding tsunami mitigation strategies are explained.

Since the 2004 Indian Ocean Tsunami, there is a growing awareness of the risks that tsunamis pose to coastal communities. Despite the fact that the population of some countries such as Chile and Japan were aware of such events, many other places had virtually not heard about such phenomenon before 2004. Nevertheless, the frequent reoccurrence of major tsunamis in recent years has led to a heightened state of tsunami awareness in many areas of the world, which can be described by an increased knowledge, disaster preparedness and willingness of local populations to evacuate when the threat of these events arises. However, the response of different elements of society to tsunami warnings nowadays still appears to be inadequate a times, pointing to lack of awareness by at least some individuals, an over-reliance in defence mechanisms or lacking in the transmission of knowledge from previous events. This paper will explore these cultural issues using as a basis observations made by the authors during field visits to areas afflicted by the last three major events (Chile, Indonesia, and Japan). The level of tsunami awareness prior to these events will be explored through an analysis on the existence of multiple layers of safety against tsunami developed by previous generations, and whether these had been preserved over time. The potential impact of these major tsunamis in the development of tsunami awareness will be analysed based on questionnaires that indicate the willingness of local coastal communities to invest in disaster preparedness.

This paper compares two different types of storm surge disaster based on field surveys. Two cases: a severe storm surge flood with its height of over 5 m due to Typhoon Haiyan (2013) in Philippine, and inundation of storm surge around Nemuro city in Hokkaido of Japan with its maximum surge height of 2.8 m caused by extra-tropical cyclone are taken as examples. For the case of the Typhoon Haiyan, buildings located in coastal region were severely affected due to a rapidly increase in ocean surface. The non-engineering buildings were partially or completely destroyed due to their debris transported to an inner bay region. In fact, several previous reports indicated two unique features, bore-like wave and remarkably high speed currents. These characteristics of the storm surge may contribute to a wide-spread corruption for the buildings around the affected region. Furthermore, in the region where the surge height was nearly 3 m, the wooden houses were completely or partially destroyed. On the other hand, in N...

Debris loads during flood events have been well-documented by forensic engineering field surveys of affected communities. Research has primarily focused on debris impact loading and less emphasis has been placed into quantifying the loads and effects associated with debris damming, which occurs when solid objects accumulate at the front of structures. The formation of the debris dam has been shown to results in increased drag forces, backwater rise, and flow accelerations which can influence the stability of the structure. This study examined the formation of a debris dam in steady-state conditions of debris common to flood-prone communities. The study determined that the hydraulic conditions, in particular flow velocity, influenced the formation of the debris dam. Additionally, the study examined the influence of the blockage ratio on the backwater rise as well as the drag coefficient.

Since 2004 there is a growing global awareness of the risks that tsunamis pose to coastal communities. Despite the fact that these events were already an intrinsic part of the culture of some countries (such as Chile and Japan), in many other places they had been virtually unheard of before 2004. Nevertheless, the frequent reoccurrence of these events in recent years has led to the emergence of a “tsunami culture” in many areas of the world, which has resulted in increased awareness, disaster preparedness and willingness of local populations to evacuate when the threat of these events arises. This paper will explore these cultural issues using as a basis questionnaires carried out by the authors during their own field visits to the last three major events (in Japan, Chile and Indonesia), and interpret these through the willingness of coastal communities to build protection measures along the shore and the impact that these can have on sustainable development.

Flood disasters such as dam breaks and surges from extreme hurricanes or tsunamis entrain and transport substantial amounts of submerged or floating debris. Understanding of motion and spatiotemporal distribution of debris entrained by a flood is thus of great importance to hydraulic, coastal, and structural engineers; the displacement of debris to a location where it may eventually impact critical infrastructure requires scientific attention at the laboratory scale first. In this context, the design and application of a novel smart debris system utilizing off-the-shelf components is presented and discussed. The system tracks the spatial location and orientation of a multitude of debris specimens and it proposes an accurate tool to assess their individual trajectory, velocity, and momentum in a laboratory environment. Contrary to the traditional camera-based approach of video tracking, which often fails once objects are submerged, the proposed smart debris system delivers six-degree-of-freedom (6D...

Thin coastal dykes typically found in developing countries may suddenly collapse due to rapid land subsidence, material aging, sea-level rise, high wave attack or a collision with vessels. Such a failure could trigger a dam-break tsunami-type flood, or dyke-break induced tsunami, a possibility which has so far been overlooked in the field of coastal disaster science and management. To analyze the potential consequences of one such flooding event caused by a dyke failure, a detailed hydrodynamic model was constructed based on the authors’ field surveys of a vulnerable coastal location in Jakarta, Indonesia. Under a 2-m land subsidence scenario – which is expected to take place in the study area after only 10 years, the model results show that the flood waters rapidly rise to a height of nearly 3 m, resembling the flooding pattern of earthquake-induced tsunamis. The depth–velocity product criteria suggests that many of the narrow pedestrian paths behind the dyke could experience strong flows, which are far greater than the safe limits that would allow pedestrian evacuation. A couple of alternative scenarios were also considered to investigate how such flood impacts could be mitigated by creating a mangrove belt in front of the dyke as an additional safety measure. The dyke-break induced tsunamis, which in many areas are far more likely than regular earthquake tsunamis, cannot be overlooked and thus should be considered in disaster management and urban planning along the coasts of many developing countries.

El 11 de Marzo del 2011 un terremoto de magnitud 9.0 en la escala Richter generó un devastador tsunami que arrasó una extensa área de la costa noreste de Japón. El Gran Terremoto y Tsunami del Este ha sido descrito como un evento que solo sucede una vez cada varios miles de años aproximadamente, y como consecuencia de éste es necesario que la filosofía sobre Gestión de Desastres Naturales en Japón sea revisada para tener en cuenta varias lecciones aprendidas a raíz de este desastre. En este artículo los auotres presentan los resultados de investigaciones de terreno en el área de Tohoku. Se detalla el daño en varias localidades y se analizan los mecanismos de daño sobre diversos tipos de estructuras. Los autores también presentan una serie de cambios que están ocurriendo en la filosofía de gestión de riesgos en Japón. Esencialmente, la idea que sólo los métodos de infraestructura física son siempre capaces de proteger las vidas de la población local ha sido descartada, y aunque se mantiene la idea de que estos métodos pueden resultar útiles para la protección de las propiedades, en última instancia los métodos de planificación deberían formar la pieza más importante del sistema de medidas para la protección de las vidas de las personas en estas áreas.

Extreme coastal events such as the 2004 Indian Ocean Tsunami, the 2011 Tohoku Tsunami as well as the 2005 Katrina and 2012 Sandy hurricanes demonstrated that, hydrodynamic loading aside, debris loading represents a major factor in the extreme loading conditions experienced by inland infrastructure. While extreme hydrodynamic loading due to coastal flooding events has been the object of intense research over the past decade, few studies dealing with debris impact due to coastal flooding have been conducted. Post-tsunami forensic engineering field investigations conducted by the authors (Nistor et al. 2005; Shibayama et al., 2006; Nistor et al. 2010) or other researchers (Chock et al. 2012, Sato et al. 2014;) revealed that debris loading and debris damming have a significant effect on the structural integrity of buildings and infrastructure in general, especially in high-density urban areas. Current design guidelines (FEMA P-55, 2011; FEMA P-646, 2012) and the new ASCE-7 Chapter 6 - Tsunami Effects and Loads suggest conservative estimations of the debris spatial spreading based on limited sets of field data to assess debris impact potential (Chock et al., 2012; Naito et al., 2014). The primary objective of this study was to investigate the spatial and temporal displacement of floating debris due to rapid coastal flooding in a built-in port environment using two novel different measuring techniques: (1) high-accuracy video debris detection and tracking system and (2) a real-time locating “smart” sensor-tracking system. Results are compared with prescriptions of the ASCE7 Chapter 6 pertaining to debris motion.

Chañaral is a town located at the mouth of the Salado River in northern Chile (Lat 26.3 °S). The main economic activity in its vicinity is copper mining, such as at Potrerillos and El Salvador. The river mouth is typically closed due to the coastal sediment transport. In addition, a large reclamation area was built from mine tailings and a highway was constructed on an elevated levee in the reclamation area. Furthermore, Chañaral is under tsunami hazard, with the last tsunami event taking place in 1922. According to historical records, the tsunami reached 10 m (Soloviev & Go, 1975). This event occurred prior to the deposition of mine tailings, which started in 1930. The official tsunami inundation map was made in 2014, and the tsunami scenario considered an extreme event based on the 1922 tsunami plus a high tide (SHOA, 2014). The maximum tsunami runup was estimated to be 17 m. In March 2015, a heavy rain event took place over the Atacama Desert and a catastrophic flood affected Chañaral, with a maximum water depth of 4.5 m (Wilcox et al., 2016), significantly changing the coast. In fact, the elevated highway was destroyed and there was substantial coastal erosion. The present work assesses the tsunami hazard considering the new coastal morphology, given that coastal erosion would allow a tsunami to easily surge into the river and subsequently the town.

Aircraft control system is designed to provide adequate stability during transition flight of a quad-tilt wing (QTW) UAV. The dynamic inversion method, which is a linearization method without an approximation algorithm, is applied to a control problem of the UAV, because of strong nonlinearity of its dynamical behavior. The validity of the proposed control system is verified through numerical simulation and experiment.

In recent years, many tsunami disasters have taken place in small remote islands, which can be considered to be particularly vulnerable against coastal disasters. In this chapter the authors discuss how to prepare for future tsunami threats in remote islands based on the results of their own field surveys conducted after two recent tsunami events. First, the results of the surveys on the 2009 Samoan and 2010 Mentawai islands tsunamis are summarized, providing the measured tsunami heights at a variety of locations. Then, the lessons learnt from the Samoan and Mentawai islands cases are described from two points of view: triggers for evacuation actions and evacuation routes and areas. Ground shaking due to an earthquake, information through a tsunami warning system, and unusual behavior of the sea are typical triggers for tsunami evacuation actions and it is important to increase the number and types of triggers. Preparing evacuation routes and signs, which can help people evacuate to higher ground quickly, are also important countermeasures against tsunamis in remote islands.

The combined effect of an increase in typhoon intensity and sea level rise could pose significant challenges to coastal defences around Tokyo Bay. In the present chapter the authors determined the storm surge that could result from an increase in typhoon intensity around Tokyo Bay around the turn of the twenty-first century. This was then combined with a variety of sea level rise scenarios to obtain potential water levels for a 1 in 100 year design storm in the year 2100. The results show that the various settlements around Tokyo Bay, and particularly those along the low-lying areas in the Koto delta in Tokyo, are at considerable risk of storm surges and sea level rise in the future. If these defences are breached the potential direct economic consequences would be significant, potentially in excess of 100 trillion yen (around 0.92 trillion USD or 0.72 trillion euros, or 20% of the current GDP of Japan), with the indirect costs likely to be even greater. As a result it is likely that sea defences will have to be strengthened around Tokyo Bay in the future, which could cost in the order of 370 bn yen to defend against a 1 in 100 year storm by the year 2100. Alternatively, a storm surge barrier could be built, which would cost in the range of 700-800 bn yen, though such a structure could raise the protection level and cope with a 1 in 500 year storm, amongst other benefits.

Coastal dikes, breakwaters, and seawalls are generally used to control floods, debris flows, erosion, and even massive catastrophic events such as tsunamis. However, these structures will only perform well if they are firmly constructed in terms of strength and stability of slopes and toes and can resist the dynamic forces imposed by the incident wave energy. During a Level 2 tsunami such as the 2011 Tohoku Earthquake Tsunami many concrete coastal defenses in the NE of the country could not withstand the forces imposed by the tsunami overflowing water and as a result failed either partially or completely. The authors carried out detailed field surveys in Miyagi and Fukushima prefectures during the period from 2011 to 2013 in order to explore the failure modes and mechanisms of coastal structures due to the 2011 Tohoku Earthquake Tsunami. Eight locations which were severely affected by this event were considered in the analysis. Subsequently, six major failure modes could be identified from the collected field data, namely: (i) leeward toe scour failure, (ii) crown armor failure, (iii) leeward slope armor failure, (iv) seaward toe scour and armor failure, (v) overturning failure, and (vi) parapet wall failure. At most surveyed locations the critical failure mode was identified as the scour initiated at the leeward toe. The present chapter discusses all six failure mechanisms, highlighting how the lessons learnt from them can help to improve the design of coastal structures under tsunami attack.

Despite the regularity with which tsunami waves attack a variety of countries around the world, comparatively little attention has been paid in the past to the design of tsunami-resilient breakwaters. This chapter will highlight some of the problems related to the failure mechanisms of caisson and armored caisson breakwaters against tsunami attack, focusing mainly on two modes: bearing capacity failure at the heel of the caisson and the stability of primary armor units. A methodology for the design of such armor will be provided for the case of overtopping waves, based on real life analysis of the failure of such armor. This method takes into account not only the tsunami level and height, but also the function of the structure (in terms of the importance of what it has been designed to protect), highlighting the need for an approach that can minimize the cost of such countermeasures.

On October 29, 2012, Hurricane Sandy made landfall along the eastern coast of the United States, generating a storm surge that caused serious damage to New York City and its vicinity. The authors carried out a post storm surge field survey in New York City, including Manhattan and Staten Island, to clarify the distribution of storm surge heights and the damage to infrastructures along urban waterfront areas. The inundation heights were 2.5 to 3 m along the southern coast of Manhattan and around 4 m along the southern coast of Staten Island. In the south part of Manhattan many types of infrastructure, such as the subway system, tunnels under the river, and an electric substation, were damaged due to flooding of their underground facilities. Prior to the hurricane’s landfall, the city prepared reasonably well against the storm surge (a mandatory evacuation order was issued and a suspension of the rapid transit system was carried out) and these measures contributed to reducing damage, though it appears to still be necessary to increase residents’ awareness of such disasters. Preparation efforts for the storm arrival contrast markedly to the poor state of preparedness of the city’s infrastructure, which were clearly not designed to cope with a storm surge and which should be significantly improved.

Vietnam, with 3260 km coastline and two vast low-lying deltas (the Red River Delta and Mekong Delta), could be considered one of the most vulnerable countries against coastal disasters and climate change. However, it appears that people outside Vietnam do not notice the vulnerability of this country's coasts against disasters, and even the vast majority of Vietnamese people may not be aware of the extent of the perils faced by their neighboring coastal communities, even though they suffer from frequent coastal floods. The challenges faced by this country in the future will have important regional and global repercussions. This chapter briefly examines threats such as tropical cyclones, sea-level rise, flooding, and coastal erosion in Vietnam. The authors wish this chapter to be an important source of information for all those who are looking at the challenges posed by impending coastal problems in Vietnam as well as other developing countries.

The 2004 Indian Ocean tsunami was the first significant transoceanic tsunami in the digital age, allowing the population of the entire world to witness the destructive power of such phenomena. Despite the fact that such events form part of the culture of countries such as Chile and Japan, many other places had virtually not heard about them before 2004. However, subsequent events in the past 10 years have led to the emergence of a heightened stage of tsunami awareness not only in countries affected recently by these events, but also in other countries which have not experienced them for a long time, such as Vietnam. The present chapter will analyze tsunami awareness in 3 countries—Chile, Indonesia, and Japan—that recently experienced a tsunami and contrast them to the case of Vietnam. The analysis will include observations on whether a multi-layer-countermeasure system existed in each area, together with interviews conducted with local residents to understand their awareness about such events. It is clear that awareness in all countries has greatly increased, though further efforts are required to increase resilience so that the inhabitants of coastal areas are adequately protected.

The present chapter describes the characteristics of the massive storm surge generated by the 2013 Typhoon Yolanda (Haiyan), which made landfall on the coast of the Philippines on November 2013. The authors conducted a series of field surveys and numerical analysis in Leyte and Samar Islands in the aftermath of the disaster in order to understand the characteristics of what constituted an almost unprecedented event in the modern era. As a result it was revealed that Yolanda struck Leyte Island at near peak strength, with maximum sustained wind speeds of 160 knots, the strongest in the recorded history of the Western North Pacific. The weather system approached land very quickly, with a forward speed of 41 km/hr as it reached Leyte, which was also one of the fastest among typhoons in the past 6 decades. As a result, Yolanda caused the largest storm surge in the recorded history of Philippines. Storm surge field surveys conducted by the authors recorded a maximum inundation height of 7 m at Tacloban, located at the northern end of Leyte Gulf. Through their interviews with local population and officials, the authors also found that water levels at some locations first lowered and then rapidly began to increase, which is in good agreement with the results of the numerical simulations carried out.

On the 11th of March 2011 an earthquake offshore the northeast coast of Japan generated a huge tsunami which overwhelmed coastal defences and inundated extensive areas of the Tohoku coastline. Japan was considered to be well prepared against such disasters but nevertheless casualties were high, though death rates were not homogeneous within the affected regions. In the present paper the authors investigate the relationship between human damage, maximum tsunami wave height and arrival time during the 2011 Tohoku Earthquake Tsunami. Generally speaking, the results indicate a positive correlation between the casualty rates inside inundated coastal settlements and tsunami height and a negative one regarding the arrival time (i.e. longer arrival times allowed residents more time to successfully evacuate). Based on these results a new tsunami category is introduced to clarify the potential threat that various earthquake scenarios pose to coastal communities in the Kanto area in Japan. These results contain useful insights for managing risks and prioritizing the investment in tsunami countermeasures to reduce future human suffering due to these disasters.

The Vietnamese coast faces the East Sea, which has been recognized as having the potential to generate devastating tsunamis, thus requiring a careful consideration of tsunami risk. In this chapter, tsunami risk and vulnerability are analyzed based on the numerical simulation of tsunami propagation and the social and geographical background of Vietnam. The numerical simulation of a potentially hazardous earthquake scenario in the Manila Trench shows the distributions of the maximum tsunami amplitude and arrival time along the Vietnamese coast. When discussing the vulnerability of the coastline, particular attention is given to three main elements affecting this type of potential disaster in Vietnam: the extensive area of low-lying ground, namely large deltas; a lack of past experience regarding tsunami events; and underdeveloped tsunami mitigation measures. Tsunami mitigation measures implemented recently in coastal communities in Vietnam, such as tsunami warning stations and tsunami drills, are also mentioned.

Sea level rise and an increase in typhoon intensity are two of the results expected from future climate change. In the present work a methodology to change the intensity of tropical cyclones in Japan is developed based on the work of Knutson and Tuleya (2004). An example of how this would affect one of the worst typhoons to hit the Tokyo Bay area in the 20 century was thus developed, highlighting the considerable dangers associated with this event, and how current sea defences could be under danger of failing by the end of the 21 century.

On 11 March 2011, an exceptionally large tsunami event was triggered by a massive earthquake offshore, the northeast coast of Japan, which affected coastal infrastructure such as seawalls, coastal ...