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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 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.

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.

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...

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.

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.

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 ...

Typhoon Haiyan (Yolanda) struck the islands of Leyte and Samar, the central part of the Philippines, on 8 November 2013, bringing large-scale devastation to coastal areas due to the high winds and large storm surge and waves associated with it. In order to obtain the distribution of storm surge heights and damage covering the wide stretch of affected coastline, the authors carried out a series of field surveys in the aftermath of the typhoon (in December 2013, May 2014, and October 2014). In the present paper, the authors detailed the results of these field surveys and summarized the characteristics of the storm surge and main causes of the damage, especially focusing on the Leyte Gulf coast, which is surrounded by the eastern coast of Leyte and the southern coast of Samar. Finally, the wide range of types of storm surge disasters were also discussed by comparing Typhoon Haiyan with other recent major events.

Japan has a long stretch of coastal dykes along its shoreline to protect against many types of coastal disasters. The 2011 Tohoku Tsunami caused serious damage to these coastal dykes along the long coastaline. One of the main reasons of the coastal dyke failure was overflowing tsunamis. Thus, after the 2011 Tohoku Tsunami, many studies on coastal dyke failure due to overflowing tsunamis have been conducted. The present study aimed to analyze the basic hydraulic characteristics of overflowing tsunamis on coastal dykes. First, the characteristics of overflowing tsunamis on coastal dykes observed during the 2011 tsunami were described using field data. The field data showed that there were different types of overflowing tsunamis during the 2011 tsunami and these types could be related to coastal dyke failure. Then, flow geometry were discussed based on the classification presented by Hom-ma (1940). Finally, the relationships between the hydraulic characteristics of overflowing tsunamis around coastal dykes (velocity field and pressure profile) and coastal dyke failure were discussed in detail by means of both laboratory investigations and numerical experiments.

Many coastal dikes in Iwate, Miyagi and Fukushima prefectures in Japan were damaged due to the 2011 Great Eastern Japan Earthquake Tsunami. The primary failure mode of these dikes was scour failure at the leeward toe by the overflowing tsunami. However, the forces exerted by the tsunami wave against the dikes were reduced to the presence of some obstacles (such as trees) located behind the dikes, increasing the tsunami inundation height immediately behind the structure and actually helping to reduce the force on the dike itself. In order to analyze how tsunamis affected coastal dikes, the authors carried out post-tsunami field surveys and laboratory tests using dikes and different coastal forest models. The critical failure mechanism of dikes was analyzed and co-related to tsunami overflowing pattern. In addition, the experimental results show how coastal forest can help to reduce the damage caused by the tsunami to coastal dikes by increasing water depth and changing the tsunami motion pattern. Thus, the placement of coastal forests behind dikes can help to increase their resilience against tsunami attack, and should be considered as part of a disaster management strategy for certain tsunami prone areas.

At 14:46 local time on March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake generated a tsunami that struck Japan as well as various locations around the Pacific Ocean. With the participation of about 300 researchers from throughout Japan, joint research groups conducted a tsunami survey along a 2,000 km stretch of the Japanese coast. More than 5,200 locations have been surveyed to date, generating the largest tsunami survey dataset in the world. The inundation height and run-up height were surveyed by laser, GPS, and other instruments, and the tidal correction has been accurately adjusted using a tidal database and a numerical simulation for Tohoku, an area where tide gauges were destroyed by the tsunami. Based on the survey dataset, the regional and local scale analyses were conducted to understand the basic characteristics of this event. Maximum run-up heights greater than 10 m are distributed along 500 km of coast in direct distance. The affected area of this event was several times larger than historically recorded in Tohoku. The mean inundation height in the southern Sanriku region is 10–15 m and there are several peaks of inundation along the coast from the northern to middle part of Sanriku.

At 14:46 on March 11, 2011 (local time), a large earthquake of magnitude Mw 9.0 took place, generating a tsunami that caused severe damage to the east coast of Japan. To comprehensively record tsun...

During the 2009 Samoan Islands Tsunami, the wide coral reef platform in front of the islands affected the approaching tsunami behavior. This research aims to understand the characteristics of a tsunami propagating over a reef platform by using a turbulence model. A Large Eddy Simulation (LES) model was used to simulate wave breaking and energy dissipation. The results of numerical simulations by using LES model were shown to reproduce well the results of the field survey in the 2009 Samoan Islands Tsunami. The present method may also apply to other countries which have coral reefs and contribute to regional tsunami mitigation strategies. It is important to understand what is the phenomenon that people in coastal areas actually experience as well as the height and arrival time of a tsunami.

Post-tsunami field surveys carried out after the 2011 Great Eastern Japan Earthquake Tsunami revealed that scour around the landward side of concrete sea dikes and seawalls was the most dominant failure mechanism. To better understand this phenomenon, detailed scour data were collected and soil samples from the surveyed locations in Miyagi and Fukushima Prefectures of Japan were comprehensively analysed. Mathematical modeling technique was employed with various combinations of input variables considered in order to determine the effective variables needed to predict the representative scour depth at the leeward of a concrete sea dike or seawall and possible design of these coastal structures against tsunami impact. Parameters such as impact overflowing pressure, height of structure measured at the landward side, inundation height, inundation velocity, angle of landward slope, Darcy’s coefficient of permeability and scour depth were found to be the effective parameters essential to generate proposed scour depth predictive model. The results indicate that the hydrodynamic parameters, soil properties and physical geometry of coastal structure play a crucial role in the scour process of such structures. In addition to that, numerical experiments were also performed in order to understand the characteristics of tsunami flow around a typical coastal dike, and to propose preliminary guidelines for structure resilience against future tsunamis.