geosciences

Article Field Survey of 2018 Jebi in : Lessons for Disaster Risk Management

Tomoyuki Takabatake 1,*, Martin Mäll 1 , Miguel Esteban 1, Ryota Nakamura 2, Thit Oo Kyaw 1, Hidenori Ishii 1, Justin Joseph Valdez 1, Yuta Nishida 1, Fuma Noya 1 and Tomoya Shibayama 1

1 Department of Civil and Environmental Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan; [email protected] (M.M.); [email protected] (M.E.); [email protected] (T.O.K.); [email protected] (H.I.); [email protected] (J.J.V.); [email protected] (Y.N.); [email protected] (F.N.); [email protected] (T.S.) 2 Department of Architecture and Civil Engineering, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580, Japan; [email protected] * Correspondence: [email protected]; Tel.: +81-03-5286-2946

 Received: 10 October 2018; Accepted: 7 November 2018; Published: 9 November 2018 

Abstract: struck Japan on the 4 September 2018, damaging and inundating many coastal areas along Bay due to the high winds, a , and wind driven waves. In order to understand the various damage mechanisms, the authors conducted a field survey two days after the typhoon made , measuring inundation heights and depths at several locations in Hyogo Prefecture. The survey results showed that 0.18–1.27 m inundation depths were caused by Typhoon Jebi. As parts of the survey, local residents were interviewed about the flooding, and a questionnaire survey regarding awareness of and storm surges, and their response to the typhoon was distributed. The authors also mapped the location of some of the containers that were displaced by the storm surge, aiming to provide information to validate future simulation models of container displacement. Finally, some interesting characteristics of the storm surge are summarized, such as possible overtopping at what had initially been thought to be a low risk area (Suzukaze town), and lessons learnt in terms of disaster risk management are discussed.

Keywords: Typhoon Jebi; damage patterns; storm surge; Japan; field survey; container movement

1. Introduction Typhoon Jebi, which formed on the 28 August 2018, struck Japan on the 4 September 2018, damaging and inundating many areas of the coastal cities of and Osaka (see Figure1). The weather system achieved a minimum central pressure of 915 hPa and a maximum one-minute sustained wind speed of 55 m/s (198 km/h; 31-August 09:00 JST (UTC+09:00)–02-September 00:00 JST) [1], and struck Japan as a Category 3 typhoon on the Saffir–Simpson scale. At the time of landfall it had wind speeds of over 44 m/s (158 km/h; ten-minute averaged wind speed), the strongest to hit mainland Japan in 25 years [1]. The route of the Typhoon Jebi was similar to that of the three typhoons which produced relatively high inundation heights in the past along (Figure1)[ 2,3]. As a result, Typhoon Jebi generated a storm surge in excess of Tokyo Peil (T.P. datum corresponds to mean sea level in Tokyo Bay) +3.29 m and T.P. +2.33 m at Osaka and Kobe’s tidal stations, respectively. Table1 shows a comparison of the maximum water levels recorded during this and past events. As shown, the past’s maximum water levels were exceeded at many tidal stations, though it should be noted that the maximum

Geosciences 2018, 8, 412; doi:10.3390/geosciences8110412 www.mdpi.com/journal/geosciences Geosciences 2018, 8, 412 2 of 19

Geosciences 2018, 8, x FOR PEER REVIEW 2 of 19 recorded during the event was a 3 min averaged-value, while the previous ones represented valuesrepresented that werevalues averaged that were over averaged approximately over approx 3 h.imately As the 3 h. design As the storm design surge storm level surge for level coastal for defensescoastal defenses in Osaka in and Osaka Kobe and is T.P.Kobe +3.90 is T.P. m and+3.90 T.P. m +2.80and T.P. m, respectively+2.80 m, respectively [4], most of[4], the most observed of the floodingobserved occurred flooding outside occurred of outside the coastal of the defenses coastal (e.g., defenses in several (e.g., artificialin several islands artificial in Hyogoislands Prefecture in Hyogo andPrefecture Osaka Prefectures).and Osaka Prefectures). In fact, during In the fact, event, during TV news the channelsevent, TV and news the generalchannels public and (usingthe general Social Networkpublic (using Services Social (SNS) Network such as Services twitter, facebook,(SNS) such or as instagram), twitter, facebook, reported or that instagram), several coastal reported locations that alongseveral the coastal cities locations of Osaka along and Kobe,the cities including of Osaka artificial and Kobe, islands including and Kansai artificial international islands and airport,Kansai wereinternational being flooded. airport, were being flooded.

Figure 1.1. MostMost notablenotable stormstorm tracks to affectaffect OsakaOsaka BayBay area.area. Best track data for Jebi and NancyNancy are fromfrom JapanJapan MeteorologicalMeteorological AgencyAgency (JMA) [[1,2],1,2], whilewhile Jane and Muroto’s are from NOAA’s IBTrACs database [[3].3]. Note that there isis nono pressurepressure informationinformation forfor Muroto’sMuroto’s tracktrack data.data. Table 1. Comparison of the maximum tidal levels recorded during Typhoon Jebi and past events 1.

TheTable previous 1. Comparison maximum of waterthe maximum level was tidal obtained levels from recorded JMA [1during]. Typhoon Jebi and past events 1. The previous maximum water level was obtained from JMA [1]. Time of Maximum Water Typhoons which Generated Maximum Water Level Previous Maximum Tidal Stations Level during Typhoon Jebi Previous Maximum Water Level duringMaximum Typhoon Water Jebi (T.P. 2)Time of Maximum Water Water LevelPrevious (T.P. 2) Typhoons which (JST, 4 September 2018) (Year) Level during Level during Typhoon Maximum Generated Previous TidalOsaka Stations 3.29 m 14:18 2.93 m Nancy (1961) KobeTyphoon 2.33 m Jebi Jebi (JST, 14:094 September Water 2.30 m Level Maximum Nancy (1961) Water Level Gobo(T.P. 3.16m 2) 2018) 12:48 1.63(T.P. m 2) Halong(Year) (2014) Shirahama 3 1.64 m 13:02 1.52 m Talas (2011) KushimotoOsaka 3 3.291.73 m 14:18 13:20 1.61 2.93 m m Phanfone Nancy (2014) (1961) AwayukiKobe 2.33 2.03 m 14:09 12:08 1.67 2.30 m m Halong Nancy (2014) (1961) Gobo1 Maximum water levels 3.16 m recorded during Typhoon 12:48 Jebi were 3 min averaged-values, 1.63 m while the Halong previous (2014) ones 2 Shirahamarepresented 3 values that 1.64 werem averaged over approximately 13:02 3 h. Tokyo 1.52 Peil m (T.P.) datum corresponds Talas (2011) to mean sea level in Tokyo Bay. 3 Maximum water levels at Shirahama and Kushimoto were updated again during 3 Kushimotothe passage of Typhoon 1.73 Trami m (2018), which passed 13:20 through Japan on 30 September 1.61 m 2018. Phanfone (2014) Awayuki 2.03 m 12:08 1.67 m Halong (2014) 1 As Maximum the typhoon water was levels predicted recordedto during cause Typhoon severe damage,Jebi wereJapan 3 min Meteorologicalaveraged-values, Agency while the (JMA) 2 issuedprevious a storm ones surge represented warning values to manythat were coastal averaged areas over (approximately approximately 3 6 h. h beforeTokyo Peil the (T.P.) typhoon 3 madedatum landfall), corresponds including to mean Hyogo, sea Osaka,level in andTokyo Bay. Maximum Prefectures water [levels1]. As at aShirahama result, Kobe and City Kushimoto were updated again during the passage of (2018), which passed through and Ashiya City (in Hyogo Prefecture) issued a storm surge warning together with a windstorm Japan on 30 September 2018. and wave warning on the 4th of September at 06:23 JST, and then a heavy rain warning at 09:23 JST. A flood warning was also issued at 13:48 JST in Kobe City and at 15:03 JST in Ashiya City. All of As the typhoon was predicted to cause severe damage, Japan Meteorological Agency (JMA) the warnings were downgraded to an “advisory” at 17:52 JST and were finally cancelled at 04:10 JST issued a storm surge warning to many coastal areas (approximately 6 h before the typhoon made on the 5 September 2018. The typhoon went on to cause 13 deaths and injure 741 people as landfall), including Hyogo, Osaka, and Wakayama Prefectures [1]. As a result, Kobe City and Ashiya City (in Hyogo Prefecture) issued a storm surge warning together with a windstorm and wave warning on the 4th of September at 06:23 JST, and then a heavy rain warning at 09:23 JST. A

Geosciences 2018, 8, 412 3 of 19 of 14 September 2018 [5], though most of these were due to high winds. Essentially, strong winds tore down some weak wooden constructions, and more than 22,000 houses were reported to have been damaged to some extent during the event (either due to flooding or wind damage). In Prefecture (where there are many historical buildings), several shrines were damaged due to high winds (e.g., Hirano shrine). According to a statement released by Hyogo Prefecture [6], 48 houses experienced flooding above the floor and 318 below the floor level, most of which were located in Ashiya City. Famously, the bridge linking Kansai international airport (situated in a reclaimed land offshore) to the mainland was damaged by a ship that was displaced by the strong wind and currents, resulting in approximately 3000 people needing to stay one night at this isolated island. Many of the ports in Osaka Bay also suffered minor economic damage, as some containers floated and drifted due to the storm surge. Kobe City reported that a total of 42 containers drifted away from their ports, and it took ten days to collect them all [7]. One of the defining moments in Japanese storm surge disaster management strategy was the 1959 Isewan Typhoon (Vera), which generated a 3.5 m storm surge in Ise Bay [8]. The storm easily overcame the poorly built dikes that surrounded the bay, leading to widespread inundation and the destruction of many buildings and infrastructure. Following this typhoon, the Japanese Government determined that coastal defenses around the country should be designed to resist any such event [8]. Thus, at present, the design tidal level for storm surge defenses is determined by one of the two following criteria [8]:

• The sum of the mean spring high tide level and the maximum storm surge recorded at a tide station or simulated assuming this standard typhoon (simplified Isewan Typhoon) (for the cases of major bay areas with a large population, such as Tokyo, Ise and Osaka Bays) • The highest tidal level recorded at a tide station (for the case of the central region of the ).

Nevertheless, design tidal levels are still established in a deterministic way (as opposed to calculating the return probability of certain events) and there are still a number of problems to ascertain the return period of storm surges, including a lack of historical data [8]. As explained earlier, most of the damage due to Typhoon Jebi was observed on the seaward side of the coastal defenses in Osaka Bay. However, some residential areas located inside of the coastal defenses were also inundated during this event. Given the design criteria outlined above, it would appear surprising that a typhoon such as Jebi, with a return period of approximately 1 in 25 years (in terms of the wind speed at the time of the landfall), could go on to flood residential areas inside Osaka Bay. In the present work, the authors thus set out to survey the inundation heights in some of these residential areas and attempt to find out what lessons can be learnt in terms of disaster risk management. The originality of the paper lies mainly in this last point (and therefore the authors also attempted to find out more about residents’ perception of danger and evacuation behavior), rather than the survey of the storm height (in this sense, the authors’ own measurements were sent to the Joint Japan Coastal Engineering Committee 2018 Survey Group [9], which provides a full description of the inundation depths for Typhoon Jebi). Aside from this, the authors also mapped the location of some of the containers that were displaced by the storm surge and would like to make this information publicly available.

2. Methodology A storm surge field survey was conducted two days after the typhoon made landfall (4 September 2018), concentrating on areas that were suspected of having suffered from a storm surge in Hyogo Prefecture, Japan. Specifically, the authors visited Higashi-Kawasaki town, Mikageishi town, and Fukaehama town in Kobe City, and Suzukaze town in Ashiya City (surrounded by white squares in Figure2). The main purpose of the survey was to clarify whether any of the areas had been inundated by the storm surge, and if so, determine the height of the flood. Also, the authors attempted to Geosciences 2018,, 8,, 412x FOR PEER REVIEW 4 of 19

been inundated by the storm surge, and if so, determine the height of the flood. Also, the authors understandattempted to the understand situation of the the situation affected areas,of the includingaffected areas, the extent including of the the damage extent to of coastal the damage structures to andcoastal buildings, structures and and the buildings, behavior ofand the the population behavior beforeof the population and after the before event. and after the event.

Figure 2. MapMap of of survey survey locations. locations. White White boxes boxes indica indicatete areas areas visited. visited. Rokko Rokko Island Island indicates indicates the thesuspected suspected initial initial location location of the of thedrifted drifted containers. containers.

2.1. Inundation Height Survey The preciseprecise locationlocation of of each each survey survey point point was was first first recorded recorded by usingby using GPS GPS instruments instruments (eTrex (eTrex 20XJ, Garmin20XJ, Garmin Ltd., Olathe,Ltd., Olathe, KS, USA), KS, followingUSA), following established established surveying surveying techniques techniques [10]. Then, [10]. the Then, heights the ofheights the storm of the surge storm traces surge were traces surveyed were surveyed by using by a using laser ranginga laser ranging instrument instrument (IMPULSE (IMPULSE 200LR (minimum200LR (minimum reading: reading: 0.01 m),0.01 Laserm), Laser Technology Technology Inc., Inc., Centennial, Centennial, CO, CO, USA), USA), a a prism prism andand staffs. staffs. The authors also used a salinity meter (EN-901, DRETECDRETEC Co., Ltd., Saitama, Japan) to check whether the water found in poolspools was seasea waterwater oror not.not. FindingFinding these points was more difficultdifficult thanthan duringduring tsunami events, as precipitation during the typhoontyphoon rapidly washed out water marks and diluted sea waterwater pools.pools. Thus, Thus, eyes eyes witnesses, witnesses, when when available, available, were were interviewed interviewed to corroborate to corroborate that the that marks the foundmarks werefound indeed were indeed correct. correct. Whenever Whenever possible, possible, the storm the surge storm inundation surge inundation height at height each locationat each waslocation established was established by using by the using sea waterthe sea level water as alevel reference as a reference point. However, point. However, at some at of some the survey of the pointssurvey itpoints was difficult it was difficult to reach to the reach sea, suchthe sea, as insu industrialch as in industrial areas where area thes where water the edge water is occupied edge is byoccupied private by companies. private companies. In such cases, In thesuch authors cases, calculatedthe authors the calculated inundation the height inundation by simply height adding by thesimply height adding of the the terrain, height as obtainedof the terrain, from 5 as m resolutionobtained from digital 5 elevationm resolution models digital (DEM; elevation The Geospatial models Information(DEM; The Geospatial Authority Information of Japan [11 ]),Authority following of the Japa JSCEn [11]), Joint following survey team the JSCE [9]. However, Joint survey it should team be[9].noted However, that theit should accuracy be noted of the that DEM the dataaccuracy is around of the± DEM30 cm, data and is around thus some ±30 levelcm, and ofinaccuracy thus some islevel expected of inaccuracy in such measurements.is expected in such The measuredmeasurements. inundation The measured heights were inundation corrected heights to the were tidal heightcorrected at theto the time tidal of height the storm at the surge’s time arrival.of the stor Allm thesurge’s data arrival. used in All this the paper data correspondused in this topaper this correctedcorrespond dataset. to this corrected dataset.

2.2. Location of the Displaced Containers The location location of of displaced displaced containers containers along along the the wa waterfrontterfront of Suzukaze of Suzukaze town town of Ashiya of Ashiya city was city wasrecorded recorded using using a handheld a handheld GPS GPSdevice. device. Photographic Photographic evidence evidence of the of position the position of each of eachcontainer container was wasalso alsotaken. taken.

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Geosciences 2018, 8, x FOR PEER REVIEW 5 of 19 2.3. Questionnaire Survey 2.3. Questionnaire Survey A structured questionnaire survey was administered to individuals in the residential A structured questionnaire survey was administered to individuals in the residential areas that areas that were surveyed (i.e., Higashi-Kawasaki town and Suzukaze town; see Figure2). were surveyed (i.e., Higashi-Kawasaki town and Suzukaze town; see Figure 2). Industrial areas were Industrial areas were excluded from this questionnaire survey, as it was difficult to find respondents excluded from this questionnaire survey, as it was difficult to find respondents to answer the to answer the questionnaire, and it is unlikely that anybody would have actually been present questionnaire, and it is unlikely that anybody would have actually been present at the time of the at the time of the storm surge. Each questionnaire typically took about 5–10 min to complete, storm surge. Each questionnaire typically took about 5–10 min to complete, containing 18 questions containing 18 questions about the perception of danger regarding the storm surge, evacuation, source of about the perception of danger regarding the storm surge, evacuation, source of information (e.g., information (e.g., TV, radio), preparedness before the disaster, experience with previous disasters, TV, radio), preparedness before the disaster, experience with previous disasters, and other personal andinformation other personal (e.g., age, information gender). (e.g., age, gender). TheThe questionnaire survey survey was was originally originally drafted drafted in inEnglish, English, following following that thatconducted conducted in the in thePhilippines in 2013 in 2013 after after typhoon Haiyan [12], [12 and], and then then translated translated into into Japanese. Japanese. Three Three Japanese Japanese nativenative speakersspeakers served served as enumerators.as enumerators. There There was awas total a of total 17 valid of 17 responses valid responses out of 21 administeredout of 21 questionnairesadministered questionnaires (valid rate: 81%),(valid asrate: some 81%), of as them some included of them included multiple multiple or incomplete or incomplete answers. Givenanswers. the Given limited the number limited ofnumber people of in people the streets in the of streets the residential of the residential areas surveyed, areas surveyed, the speed the in whichspeed thein which survey the was survey carried was out carried (2 days out after(2 days the after event) the and event) limitations and limitations of time, of the time, authors the considerauthors consider that there that is athere scientific is a scientific value to value these to results, these results, despite despite the comparatively the comparatively small samplesmall size.sample Nevertheless, size. Nevertheless, the limited the limited number number of respondents of respondents does does not makenot make it possible it possible to conductto conduct any detailedany detailed statistical statistical analysis, analysis, and and are are only only indicative indicative as as to to how how andand whywhy the larger larger population population of of thethe areaarea maymay havehave acted.acted. The The main main group group of of resp respondentsondents were were characterized characterized by by being being relatively relatively maturemature (over 40 years old), old), and and as as the the survey survey wa wass conducted conducted during during the the daytime daytime of a of weekday, a weekday, it itshowed showed also also a alarge large proportion proportion of ofhousewives housewives (Figure (Figure 3).3 ).

(a) (b) (c)

FigureFigure 3.3. Distribution of of respondents; respondents; (a (a) )Gender Gender distribution distribution of of respondents respondents (n (n = =17); 17); (b ()b )Age Age distributiondistribution ofof respondents (n = 17); ( (cc)) Occupation Occupation of of respondents respondents (n (n = = 17). 17).

3.3. ResultsResults

3.1.3.1. InundationInundation Heights AA summarysummary of all the locations surveyed surveyed and and the the corresponding corresponding inundation inundation height height can can be be found found inin TableTable2 2 and and FigureFigure4 4.. AsAs willwill be discussed later, later, inundations inundations at at Points Points H2, H2, H3, H3, and and M1 M1 are are likely likely to tohave have been been caused caused by water by water arriving arriving from from inland inland (such (suchas through as through manhole manholes,s, overflowing overflowing of small of smallrivers riversor due or dueto local to local topographical topographical features features including including rain rain water). water). In Incontrast, contrast, inundation inundation at at FukaehamaFukaehama and Suzukaze Suzukaze towns towns was was likely likely caused caused by bya storm a storm surge surge (and (andthus thusby sea by water). sea water). The Themaximum maximum inundation inundation height height measured measured by the by auth the authorsors was +4.34 was +4.34 m at Point m at PointS3 (Suzukaze S3 (Suzukaze town). town).

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Table 2. Survey measurement results. Inundation height is defined as the height above the local tide level during the event, while inundation depth is defined as height from the local ground level. The reliability of the measurements is classified into A, B, C, and D. A: clear mark and small possible survey error; B: unclear mark and small possible survey error; C: unclear mark and large possible survey error; and D: unclear mark, low confidence, and large possible survey error.

Inundation Height (m) Inundation No. Location Longitude Latitude Reliability Target (Height above T.P. (m)) Depth (m) 1.71 1 flood from H1 Higashi-Kawasaki town 135◦10052.5” 34◦40034.3” 0.70 B (T.P. +2.21) image 1.39 1 H2 Higashi-Kawasaki town 135◦10052.3” 34◦40034.2” 0.38 B water mark (T.P. +1.89) 2.29 1 H3 Higashi-Kawasaki town 135◦10052.4” 34◦40032.6” 0.68 B water mark (T.P. +2.79) 1.93 1 M1 Mikageishi town 135◦15010.1” 34◦42034.9” 0.20 B water mark (T.P. +2.43) 2.10 1 F1 Fukaehama town 135◦1804.7” 34◦42021.8” 1.27 B Debris (T.P. +2.60) 2.92 1 F2 Fukaehama town 135◦17059.9” 34◦42034.6” 0.79 B water mark (T.P. +3.42) 1.80 1 F3 Fukaehama town 135◦17053.5” 34◦42045.9” 0.95 B water mark (T.P. +2.30) 4.31 S1 Suzukaze town 135◦18054.5” 34◦42022.0” 0.64 A water mark (T.P. +4.81) 4.25 S2 Suzukaze town 135◦18054.3” 34◦42023.7” 0.35 A Debris (T.P. +4.75) 4.34 S3 Suzukaze town 135◦18055.6” 34◦42025.3” 0.42 A water mark (T.P. +4.84) 4.03 S4 Suzukaze town 135◦18055.4” 34◦42027.9” 0.33 A water mark (T.P. +4.53) 3.28 S5 Suzukaze town 135◦18055.1” 34◦42028.7” 0.18 A water mark (T.P. +3.78) 1 The inundation heights at locations H1–3, M1, and F1–3 are calculated using the DEM data provided by the Geospatial Information Authority of Japan, Ministry of Land, Infrastructure, Transport and Tourism. However, it should be noted that the altitude accuracy of the DEM data is ±30 cm.

3.1.1. Higashi-Kawasaki Town (Minato Elementary School) Higashi-Kawasaki is in the Chuo ward of Kobe City, which is known as the commercial and entertainment district of the city and is located approximately 100 m away from the sea. The authors conducted their survey at the crossroad in front of Minato elementary school. The Kobe City flood gate, 26.7 m in length and 1.3 m in height (from the local ground level), is situated at this intersection to defend the residential areas on its west side. According to the report issued by Kobe City [13], all the gates in Kobe City were ordered to be closed at 08:30 JST on 4 September 2018, and a local witness indicated that this flood gate was indeed closed before the typhoon made landfall. The inundation depth at the outside of the gate (Point H1) was measured to be 0.70 m. The authors measured this height based on a picture which was taken during the flooding and uploaded to the internet [14]. Two watermark traces were found inside the area that was supposedly protected by the gate (Points H2 and H3), with measured inundation depths of 0.38 m and 0.68 m, respectively (Figure5a,b). As the local ground level at H1 (unprotected side) is 0.10 m lower than that at the gate, water surface level at H1 is 0.70 m lower than the top of the gate. This suggests that the gate was effective in protecting the residential area from the storm surge during the peak of the typhoon, and that a different water source caused the flooding in the protected side. The locals reported that water was seen coming from manholes and flooded the area behind the gate. However, the inundation depth difference between points H2 and H3 was measured to be 30 cm, over a distance of roughly 50 m (Figure4b). These differences could be due to specific characteristics in local topography, where the land elevation behind the gate is somewhat lower than its surroundings (i.e., land elevation at H2 is higher than that at H3). This local feature, including pooling of rain water and eyewitness accounts on water intrusion through manholes, could potentially explain the inundation on the protected side of the gate. Nevertheless, no significant damage to the surrounding Geosciences 2018, 8, x FOR PEER REVIEW 7 of 19 Geosciences 2018, 8, 412 7 of 19 accounts on water intrusion through manholes, could potentially explain the inundation on the protected side of the gate. Nevertheless, no significant damage to the surrounding structures was structures was observed during the survey, though some residential houses suffered flooding to observed during the survey, though some residential houses suffered flooding to the ground floor the ground floor (and had to dry or dispose of furniture and other belongings located there). (and had to dry or dispose of furniture and other belongings located there).

FigureFigure 4.4. SurveySurvey locations; locations; (a) ( aSurvey) Survey locations locations and andmeasured measured inundation inundation height height (orange) (orange) and andinundation inundation depth depth (blue) (blue) along along Osaka Osaka Bay, Bay,showin showingg also alsothe path the pathof Typhoon of Typhoon Jebi (red Jebi line); (red line);(b) (bdetails) details of ofinundation inundation height height and and inundati inundationon depth depth at at Higashi-Kawasaki Higashi-Kawasaki town; town; and and (c ()c )Suzukaze Suzukaze town.town. The The measurement measurement heights heights areare exaggeratedexaggerated 2000:12000:1 in (a) and 50:1 50:1 in in ( (bb,,cc).).

Geosciences 2018, 8, 412 8 of 19 Geosciences 2018,, 8,, xx FORFOR PEERPEER REVIEWREVIEW 8 of 19

Figure 5.5.Photographs Photographs taken taken by theby authorsthe authors at Higashi-Kawasaki at Higashi-Kawasaki town. (a )town. Survey (a Point) Survey H2 (watermark Point H2 (watermarkon a window); on (ab )window); Survey Point (b) Survey H3 (watermark Point H3 is(watermark indicated byis indicated a yellow allow).by a yellow allow).

3.1.2. Mikageishi Town Mikageishi town at Higashinada ward, located located at at the the easternmost side side of of Kobe Kobe City, City, is mostly composed ofof residentialresidential zones. zones. The The coastal coastal defenses defenses in in the the area area is madeis made up up ofa of levee a levee with with a flood a flood gate gatesituated situated at the at entrance the entrance of the of port the storage port storage zone (Figurezone (Figure6a). The 6a). gate The was gate built was in built 1969 in and 1969 has and a length has a lengthof 10 m of and 10 heightm and of height 1.4 m, of and 1.4 was m, and closed was at closed the time atwhen the time the when typhoon the made typhoon landfall. made No landfall. significant No significantdamage could damage be observed could be duringobserved the during field survey,the field even survey, in the even port in storagethe port areastorage situated area situated outside outsideof the gate. of the Nevertheless, gate. Nevertheless, one watermark one watermark (0.20 m (0.20 from m the from ground) the ground) was found was found on the on exterior the exterior wall wallof a residentialof a residential structure structure (Figure (Figure6b), approximately 6b), approximately 200 m away200 m from away the from flood the gate. flood The gate. authors The authorsinterviewed interviewed a local resident a local regarding resident theregarding flooding the in flooding this residential in this area, residential who reported area, who that thereported water thatcame the from water a nearby came overflowingfrom a nearby river overflowing (approximately river 30(approximately m away) and receded30 m away) relatively and receded quickly. Waterrelatively in a quickly. pool near Water the water in a markpool near was foundthe wa toter have mark only was 0.2% found salinity. to have Considering only 0.2% these salinity. facts, Consideringthe authors concluded these facts, that the there authors was aconcluded high probability that there that thewas area a high suffered probability from fluvial that floodingthe area sufferedrather than from a direct fluvial storm flooding surge rather attack. than a direct storm surge attack.

Figure 6. PhotographsPhotographs taken taken byby the the authors authors at Mikageishi at Mikageishi town. town. (a) Coastal (a) Coastal levee and levee gate and at gate the entranceat the entrance of the port of the storage port storagezone; (b zone;) Survey (b) Point Survey M1 Point (watermark M1 (watermark is indicated is indicated by a yellow by allow). a yellow allow). 3.1.3. Fukaehama Town 3.1.3. Fukaehama Town Fukaehama town is also located at Higashinada ward, east of Mikageishi town, with the reclaimedFukaehama land next town to isthe also coast located being at mainly Higashinada dedicated ward, to east industrial of Mikageishi use. The town, area withis protected the reclaimed by an approximatelyland next to theT.P. coast+5.4 m being high dike mainly [15] dedicated(Figure 7a). to industrial use. The area is protected by an approximatelyThree measurements T.P. +5.4 were m high taken dike in [ this15] (Figurearea: (1)7a). the fence of an oil factory plant (F1); (2) the gate of a highThree school measurements (F2); and were (3) a taken model in thishouse area: in (1)front the of fence a department of an oil factory store plant(F3). The (F1); presence (2) the gate of debrisof a high at the school fence (F2); of the and oil (3)factory a model plant, house which in were front measured of a department to be at a store height (F3). of 1.27 The m presence above the of road,debris showed at the fence that the of thedirection oil factory of water plant, was which towards were inland measured (i.e., tosouth beat to a no heightrth; Figure of 1.27 7b). m aboveOther debris,the road, such showed as uprooted that the trees direction and ofroad water signs was that towards drifted inland with the (i.e., water south flow, to north; were Figure observed7b). aroundOther debris, the area such during as uprooted the survey trees (Figure and road 7c,d), signs though that driftedthey could with also the have water been flow, scattered were observed due to thearound highthe wind. area Significant during the inundation survey (Figure heights7c,d), were though also measured they could at a also high have school been (Figure scattered 7e) and due a modelto the highhouse wind. (Figure Significant 7f), as shown inundation in Table heights 2. Alth wereough also it is measured still not atclear a high whether school the (Figure dike was7e) overtoppedand a model by house the storm (Figure surge7f), as or shown wind-driven in Table waves,2. Although the observations it is still not indicate clear whether that the the current dike level of coastal defenses could not completely protect this district from inundation.

Geosciences 2018, 8, 412 9 of 19 was overtopped by the storm surge or wind-driven waves, the observations indicate that the current

Geoscienceslevel of coastal 2018, 8, defensesx FOR PEER could REVIEW not completely protect this district from inundation. 9 of 19

Figure 7.7. PhotographsPhotographstaken taken by by the the authors authors at Fukaehamaat Fukaehama town. town. (a) Coastal(a) Coastal dike atdike Fukaehama at Fukaehama town, (town,b) Survey (b) Survey Point F1Point indicates F1 indicates that the that direction the direction of debris of was debris towards was thetowards inland, the ( cinland,–d) Presence (c–d) Presenceof debris of at debris Fukaehama at Fukaehama town, (e) town, Survey (e Point) Survey F2 (watermarkPoint F2 (watermark at school at gate), school (f) gate), Survey (f) Point Survey F3 (watermarkPoint F3 (watermark at a model at house).a model house).

3.1.4. Suzukaze Town The survey team team also also went went to to Ashiya Ashiya City, City, located located east east of of Kobe Kobe City. City. The The residential residential area area at Suzukazeat Suzukaze town, town, which which stands stands on on a areclaimed reclaimed island island constructed constructed in in 1997, 1997, suffered suffered significant significant coastal floodingflooding during the passage of the typhoon. Although thethe area area is protectedis protected by a highby a embankment high embankment with a crest with level a situatedcrest level at approximately situated at T.P.approximately +5.6 m [15 T.P.], relatively +5.6 m [15], significant relatively inundation significant took inundation place. Shippingtook place. containers Shipping containers also drifted also to driftedthe water to frontthe water of this front area, of though this area, none though of them none were of found them onwere the found landward on the side landward of the embankment side of the (i.e.,embankment residential (i.e., area). residentia A newspaperl area). A article newspaper [16] reported article [16] that reported a local that resident a local had resident heard had the soundheard theof containers sound of containers as they collided as they with collided the embankment. with the embankment. The pedestrian The steelpedestrian railings steel at the railings water at edge the waterof the edge embankment of the embankment was bent towards was bent the towards land side, the probably land side, due probably to the collision due to the with collision the drifting with thecontainers drifting (Figure containers8a). (Figure 8a). The fivefive survey points (S1–5) are shownshown inin FigureFigure8 8b–f.b–f. TheThe maximummaximum measuredmeasured inundationinundation depth was 0.64 0.64 m m around around the the ground ground close close to to the the sea sea (at (at Point Point S1), S1), ranged ranged from from 0.33 0.33 m mto to0.42 0.42 m mat otherat other points points (S2 (S2 to toS4) S4) in inthe the middle middle section section of of this this community, community, and and dropped dropped to to 0.18 0.18 m m at at the last survey point (S5). After After correcting correcting for for tide tide levels, levels, th thisis represented represented levels levels of of T.P. T.P. +3.78 m to +4.84 m. m. The pedestrian road near the top of embankment was severely eroded (See Figure8 8g),g), andand muchmuch sand was transported into the residential area (in fact, the authors observed that the transported sand was being cleaned while they conducted the survey).survey). The locals whom the authors interviewed reported that a power outage took place afterafter thethe waterwater invadedinvaded thethe residentialresidential area.area. Overall, the the results results indicate indicate that that the the embankment embankment height height was was not not sufficiently sufficiently high high to protect to protect the areathe area against against the theflooding flooding brought brought about about by by Typhoon Typhoon Jebi. Jebi. It Itis is interesting interesting to to note note that that the the sea sea water water overtopped the the road road embankment embankment (which (which had had an elevat an elevationion of T.P. of +5.6 T.P. m), +5.6 despite m), despitethe fact thethat factthe maximumthat the maximum water level water recorded level recorded at Osaka at Osaka and Kobe and Kobe tidal tidal station station were were T.P. T.P. +3.29 +3.29 m m and and +2.33 +2.33 m, m, respectively. BasedBased on on field field observations observations and and the the reports reports of localof local witnesses, witnesses, this overtoppingthis overtopping could could have havebeen causedbeen caused by a combination by a combination of a storm of a surgestorm and surge associated and associated high waves. high Local waves. witnesses Local witnesses reported veryreported strong very winds strong in Suzukaze winds in town Suzukaze before thetown seawater before overtoppedthe seawater the overtopped embankment. the Thus, embankment. the storm Thus, the storm surge height around this point should have been relatively high. However, as the measured inundation depths are not so large, the authors think that the storm surge height (tidal level) might not have exceeded the height of the embankment. Therefore, seawater intrusion to the landside area could have occurred due to a combination of an already high tidal level and wind waves, resulting in waves running up the slope of embankment and therefore overtopping it.

Geosciences 2018, 8, 412 10 of 19 surge height around this point should have been relatively high. However, as the measured inundation depths are not so large, the authors think that the storm surge height (tidal level) might not have exceeded the height of the embankment. Therefore, seawater intrusion to the landside area could

Geoscienceshave occurred 2018, 8, due x FOR to PEER a combination REVIEW of an already high tidal level and wind waves, resulting in waves10 of 19 running up the slope of embankment and therefore overtopping it. However, in order to clarify this However,mechanism, in it order will beto necessaryclarify this to mechanism, conduct a detailed it will numericalbe necessary simulation to conduct of the a stormdetailed surge, numerical and to simulationalso consider of the effectstorm ofsurge, wind and waves. to also consider the effect of wind waves.

Figure 8. Photographs taken by the au authorsthors at Suzukaze town. ( a) Damaged steel barrier and drifted shipment container at the embankment; ( b–f) Survey Points S1–S5, respectively (watermark is highlighted with a yellow dashed line); (g) Eroded pedestrianpedestrian roadroad nearnear thethe coastalcoastal embankment.embankment.

3.2. Location of Containers Table3 3 and and FiguresFigures9 9and and 10 10 provide provide the the location location of of the the containers containers found found at at the the waterfront waterfront of of Suzukaze town, Ashiya City, with the type and size of each container (following the ISO standards, when available). As No. 11 and 13 are containers used for domestic transportation, ISO types are not assigned toto them,them, but but the the size size could could be obtained be obtained by referring by referring to the Japanese to the Japanese standards. standards. Six containers Six containershad been washed had been away washed in front away of the in embankment,front of the embankment, and 8 on the and beach. 8 on According the beach. to According a report issued to a reportby Ashiya issued City by [Ashiya17], a total City of[17], 18 a containers total of 18 driftedcontainers to Ashiya drifted City,to Ashiya and allCity, of themand all were of them removed were removedon the 8th on of the September, 8th of September, two days two after days the after survey. the All survey. of the All containers of the containers that arrived that atarrived the front at the of frontthe embankment of the embankment were large were (40 larg feete high,(40 feet ~12.2 high, m), ~12.2 while m), those while found those on found the beach on the were beach of were a smaller of a smallertype (20 type feet, ~6.1(20 feet, m), though~6.1 m), the though reason the for reason this segregation for this segregation is not known is bynot the known authors. by Thethe authors. doors of Thecontainers doors No.of containers 7 and No. No. 13 were 7 and open, No. and 13 werewere confirmedopen, and by were the authorsconfirmed to beby empty. the authors The authors to be empty.asked Ashiya The authors City whereasked Ashiya they thought City where the containers they thought came the from. containers However, cameas from. of September However, 14th,as of Septemberthis was still 14th, not clear,this thoughwas still it isnot highly clear, likely though that it they is highly originated likely from that the they southeast originated container from berth the southeastat Rokko Island,container in Kobeberth City at Rokko (See Figure Island,2). in Kobe City (See Figure 2).

Geosciences 2018, 8, 412 11 of 19 GeosciencesGeosciences 2018 2018, 8, ,x 8 FOR, x FOR PEER PEER REVIEW REVIEW 11 of11 19of 19

FigureFigure 9. Bird’s9. Bird’s eye view view of ofthe the reclaimed reclaimed land land of ofAs Ashiya Ashiyahiya City City and and the the location location of ofthe the containers, containers, whosewhose coordinate coordinate areare are shownshown shown inin TableTablein Table3 .3. 3.

Figure 10. Photographs of the displaced containers. The numbers correspond to the identification FigureFigure 10. 10. Photographs Photographs of ofthe the displaced displaced containers. containers. Th The numberse numbers correspond correspond to tothe the identification identification numbers of each container shown in Table3. numbersnumbers of eachof each container container shown shown in Tablein Table 3. 3.

Geosciences 2018, 8, x FOR PEER REVIEW 12 of 19

Table 3. Location of the drifted containers.

Size (Length/Width/Height) No. Longitude Latitude Type Geosciences 2018, 8, 412 (mm) 12 of 19 1 34°42′18.68′′ 135°19′6.96′′ 45R1 12,192/2438/2896 2 34°42′19.15′′ 135°19′1.2′′ 45U1 12,192/2438/2896 3 34°42′19.48′′ Table135°18 3. Location′56.52 of′′ the drifted45G1 containers. 12,192/2438/2896 4 No.34°42 Longitude′19.58′′ Latitude135°18′56.52 Type′′ Size45G1 (Length/Width/Height) 12,192/2438/2896 (mm) 5 34°42′19.8′′ 135°18′53.64′′ 45G1 12,192/2438/2896 1 34◦42018.68” 135◦1906.96” 45R1 12,192/2438/2896 6 2 34°4234′◦20.4542019.15”′′ 135135°18◦1901.2”′47.16 45U1′′ 45G1 12,192/2438/2896 12,192/2438/2896 7 3 34°4234′◦22.3942019.48”′′ 135135°18◦18056.52”′42.8445G1′′ 45GI 12,192/2438/2896 12,192/2438/2896 ◦ 0 ◦ 0 8 4 34°4234′22.942 19.58”′′ 135135°1818 56.52”′42.4845G1′′ 45R1 12,192/2438/2896 12,192/2438/2896 ◦ 0 ◦ 0 9 534°42 34′30.142 19.8”′′ 135135°1818 53.64”′40.3245G1′′ 22G1 12,192/2438/2896 6058/2438/2591 6 34◦42020.45” 135◦18047.16” 45G1 12,192/2438/2896 1 10 7 34°4234′◦29.2742022.39”′′ 135135°18◦18042.84”′33.4845GI′′ - 12,192/2438/2896 3.66 m/2.42 m/2.59 m 11 834°42 34′29.26◦42022.9”′′ 135135°18◦18042.48”′31.4045R1′′ - 12,192/2438/2896 6058/2438/2591 12 934°42 34′29.12◦42030.1”′′ 135135°18◦18040.32”′31.3222G1′′ 22G1 6058/2438/2591 6058/2438/2591 ◦ 0 ◦ 0 1 13 1034°4234′29.3842 29.27”′′ 135135°1818 33.48”′31.06′′ - - 3.66 m/2.42 m/2.59 6058/2438/2591 m 11 34◦42029.26” 135◦18031.40” - 6058/2438/2591 14 34°42′29.27′′ 135°18′30.96′′ 22G1 6058/2438/2591 12 34◦42029.12” 135◦18031.32” 22G1 6058/2438/2591 1 As information13 34 regarding◦42029.38” the 135 size◦18 of031.06” this containe-r could not be 6058/2438/2591 obtained (the surface on which the type would14 have34◦ 42been029.27” written 135 was◦180 30.96”in contact22G1 with ground), 6058/2438/2591the authors measured the size by 1 Asthemselves. information regarding the size of this container could not be obtained (the surface on which the type would have been written was in contact with ground), the authors measured the size by themselves. 3.3. Questionnaire Surveys 3.3. Questionnaire Surveys 3.3.1. Perception of Danger and Experience with Previous Disasters 3.3.1. Perception of Danger and Experience with Previous Disasters The first question of the survey asked respondents if they thought that the storm surge constitutedThe first a question real danger of the for survey them. asked Figure respondents 11 and subsequent if they thought figures that show the the storm disaggregated surge constituted values afor real Higashi-Kawasaki danger for them. town Figure (n = 115) andand Suzukaze subsequent town figures (n = 12). show For the the disaggregated case of Higashi-Kawasaki values for Higashi-Kawasakitown, 3 out of 5 respondents town (n = 5) indicated and Suzukaze that the town storm (n =surge 12). constituted For the case a ofreal Higashi-Kawasaki danger for them. town,People 3 outwho of thought 5 respondents that the indicatedstorm surge that was the a stormreal danger surge for constituted them also a answered real danger that for they them. had Peopleexperienced who thought damage that during the storm a previous surge wasstorm a real surge danger (Figure for them12) and also that answered their place that theyhad hadbeen experiencedflooded during damage that during event. a In previous contrast, storm almost surge 60 (Figure% of people 12) and in thatSuzukaze their place town had thought been flooded that the duringstorm thatsurge event. did Innot contrast, represent almost a real 60% danger of people for inthem. Suzukaze This townrelatively thought low thatawareness the storm could surge be didexplained not represent by the a realfact dangerthat 90% for have them. never This relativelyexperienced low flooding awareness before could (Figure be explained 12). In byaddition, the fact a thatstorm 90% surge have hazard never experiencedmap provided flooding by Hyogo before Prefecture (Figure 12did). not In addition, show that a stormthis area surge could hazard be flooded map provided[18]. Thus, by it Hyogo might Prefecture have been did difficult not show for thatpeople this in area this could area beto understand flooded [18]. that Thus, they it mightwere in have real beendanger. difficult for people in this area to understand that they were in real danger.

FigureFigure 11. 11.Distribution Distribution of of the the opinion opinion of of respondents respondents regarding regarding whether whether they they thought thought a a storm storm surge surge waswas a a real real danger danger for for them them (n (n = = 5 5 for for Higashi-Kawasaki Higashi-Kawasaki town, town, n n = = 12 12 for for Suzukaze Suzukaze town). town).

Geosciences 2018, 8, 412 13 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 13 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 13 of 19

FigureFigure 12. Proportion 12. Proportion of respondents of respondents who havewho have experienced experienced some some sort sort of damageof damage from from aprevious a previous stormFigure surgestorm 12. (n surge Proportion = 5 for(n = Higashi-Kawasaki 5 for of Higashi-Kawasakirespondents who town, havetown, n = experien 12 n = for 12 Suzukaze forced Suzukaze some town). sort town). of damage from a previous storm surge (n = 5 for Higashi-Kawasaki town, n = 12 for Suzukaze town). 3.3.2. Preparedness3.3.2. Preparedness before before the Disaster the Disaster and Sourceand Source of Information of Information about about the the Disaster Disaster 3.3.2. Preparedness before the Disaster and Source of Information about the Disaster RegardingRegarding sources sources of information of information on the on disaster, the disaster, a relatively a relatively high percentagehigh percentage of people of people relied relied on TV or radioonRegarding TV (Figure or radio sources13 ),(Figure which of information13), is similar which to ison thesimilar the tendencies disaster, to the a observedtendencies relatively in highobserved storm percentage surges in storm in of other peoplesurges countries reliedin other (e.g.,on Philippines countriesTV or radio (e.g., for (Figure thePhilippines case 13), of which Typhoonfor the is casesimilar Haiyan of Typhoon to [the12]). tendencies Haiyan This confirms [12]). observed This that confirmsin mass storm media thatsurges mass is thein mediaother most is effectivecountriesthe way most (e.g., to effective disseminate Philippines way information tofor disseminate the case [of19 informationTyphoon]. However, Haiyan [19]. as shown [12]).However, This in Figure asconfirms shown 14, 35%that in Figure ofmass respondents media14, 35% is of answeredtherespondents most that effective this information answered way to thatdisseminate was this not information very information useful, was which not[19]. is very oppositeHowever, useful, to aswhich what shown coastal is opposite in Figure residents to 14, what reported35% coastal of in areasrespondentsresidents affected reported byanswered Typhoon in that areas Haiyan this affected information in the by Philippines Typhoon was not Haiyan [ 12very]. This useful,in the is probablyPhilippines which is due opposite [12]. to the This to fact iswhat probably that coastal no one due hadresidents predictedto the fact reported that that Suzukaze no in one areas had town affected predicted could by be Typhoon that flooded. Suzukaze Haiyan Thirty-five town in the could percent Philippines be flooded. of the [12]. respondents Thirty-five This is probably inpercent Suzukaze due of the to the fact that no one had predicted that Suzukaze town could be flooded. Thirty-five percent of the town answeredrespondents that in they Suzukaze received town information answered from that the th area’sey received loud speaker information system. from Ashiya the City area’s issued loud respondents in Suzukaze town answered that they received information from the area’s loud an evacuationspeaker system. order to Ashiya local residentsCity issued of an Suzukaze evacuation town order at to 14:50 local JSTresidents [20]. However,of Suzukaze according town at 14:50 to speaker system. Ashiya City issued an evacuation order to local residents of Suzukaze town at 14:50 the locals,JST [20]. by the However, time this according alert was to issued,the locals, the by area the had time already this alert started was issued, to be flooded,the area had and already there JST [20]. However, according to the locals, by the time this alert was issued, the area had already was a powerstarted outageto be flooded, soonafter and there the flooding was a power started, outage meaning soon after that the they flooding could notstarted, get anymeaning further that started to be flooded, and there was a power outage soon after the flooding started, meaning that informationthey could from not TV. get In addition,any further residents information reported from TV. that In they addition, could residents not hear thereported evacuation that they order could due not they could not get any further information from TV. In addition, residents reported that they could not to the stronghear the sound evacuation of rain order and due wind. to the As strong a result, sound 58% of ofrain respondents and wind. As in a Suzukaze result, 58% town of respondents answered in hearSuzukaze the evacuation town answered order due that to the they strong did not sound get anyof rain information and wind. from As a local result, authorities. 58% of respondents in thatSuzukaze they did nottown get answered any information that they did from not local get any authorities. information from local authorities.

Figure 13. Source of information on storm surge and typhoon (n = 5 for Higashi-Kawasaki town, FigureFiguren 13. = 1213.Source for Source Suzukaze of of information information town, multiple-choice on on stormstorm surge allowed). and and typhoon typhoon (n(n = 5 = for 5 forHigashi-Kawasaki Higashi-Kawasaki town, town, n= 12n = for 12 Suzukazefor Suzukaze town, town, multiple-choice multiple-choice allowed). allowed).

Geosciences 2018, 8, x FOR PEER REVIEW 14 of 19 Geosciences 2018, 8, 412 14 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 14 of 19

Figure 14. Distribution of respondent regarding whether the information they obtained on the storm surge was useful (n = 5 for Higashi-Kawasaki town, n = 12 for Suzukaze town). FigureFigure 14. Distribution 14. Distribution of respondent of respondent regarding regarding whether whethe therinformation the information they they obtained obtained on the onstorm the storm surgesurge was was useful useful (n = 5(n for = 5 Higashi-Kawasaki for Higashi-Kawasaki town, town, n = 12n = for 12 Suzukaze for Suzukaze town). town). 3.3.3. Evacuation 3.3.3. Evacuation 3.3.3.Regarding Evacuation evacuation preparedness prior to the event, 82% answered that they have never joinedRegarding anRegarding evacuation evacuation evacuation drill. preparedness Even preparedness a respondent prior toprior who the event,toan sweredthe 82%event, that answered 82% they answeredhad that joined they that havean evacuation they never have joined drillnever anindicated evacuationjoined an that evacuation drill. this Even was a drill.not respondent to Even prepare a respondent who them answered agains who thatt aan storm theyswered had surge that joined orthey tsunami, an had evacuation joined but justan drill evacuation for indicated checking drill thattheindicated this location was not thatof tothe this prepare disaster was themnot prevention to against prepare a warehouse. storm them surgeagains Ninety-four ort a tsunami, storm surge butpercent just or fortsunami,answered checking but that the just they location for didchecking ofnot theevacuate disasterthe location during prevention of thethe eventdisaster warehouse. (Figure prevention Ninety-four 15). Regarding warehouse. percent this Ninety-four answeredquestion, it that percentshould they be didanswered noted not evacuate that that respondents they during did not thewere eventevacuate being (Figure duringasked 15). if the Regardingthey event evacuated (Figure this question, to 15). somewhere Regarding it should th that beis was notedquestion, outside that it respondents ofshould the inundation be noted were beingthat area, respondents askedand thus if theyverticalwere evacuated beingevacuation asked to somewhere wasif they categorized evacuated that was as outsideto ”no somewhere evacuation”. of the inundationthat Therewas outside are area, a variety andof the thus inundationof verticalreasons evacuation citedarea, forand not thus wasevacuatingvertical categorized evacuation (Figure as ”no 16). evacuation”.was For categorized example, There 15% as are ”noof athos varietyevacuation”.e who of reasonsdid Therenot evacuate cited are fora variety notanswered evacuating of reasons that (Figurethey cited did 16for not). not Forknow example,evacuating how to 15% (Figureevacuate, of those 16). or whoFor that example, did the not ground evacuate 15% elevation of thos answerede whoof their did that area not they shouldevacuate did not be answered knowhigh enough how that to evacuate,(13%). they did 45% not orof that knowthe the respondents how ground to evacuate, elevation in Higashi-Kawasaki or of that their the area ground should town elevation beunde highrestimated of enough their area (13%).the should size 45% of be ofthe high the storm enough respondents surge. (13%). Other in 45% Higashi-Kawasakireasonsof the givenrespondents were town relatedin underestimated Higashi-Kawasaki to difficulty the sizein town getti of the undeng storm torestimated the surge. evacuation Other the size reasons area, of theor given stormnot were receiving surge. related Other an toevacuation difficultyreasons ingiven order. getting were Approximately to therelated evacuation to halfdifficulty area, the orrespondent notin getti receivingngs answeredto anthe evacuation evacuation that they order. area, would Approximately or evacuatenot receiving if half they an thefaced respondentsevacuation a similar order. answeredsituation Approximately in that the they future, would half while the evacuate othersrespondent answered if theys answered faced that a they similar that would they situation wouldnot, or in evacuatedid the not future, give if they a whileclearfaced others answer. a similar answered situation that they in the would future, not, while or did others not give answered a clear that answer. they would not, or did not give a clear answer.

FigureFigure 15. 15.Proportion Proportion of of respondents respondents who who evacuated evacuated during during the the event event (n (n = 5= for5 for Higashi-Kawasaki Higashi-Kawasaki town,town, n =n 12= 12 for for Suzukaze Suzukaze town). town). Figure 15. Proportion of respondents who evacuated during the event (n = 5 for Higashi-Kawasaki town, n = 12 for Suzukaze town).

Geosciences 2018, 8, 412 15 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 15 of 19

Figure 16. Reasons cited by respondents for not evacuating (note that multiple answers were allowed in this question, n = 4 4 for for Higashi-Kawa Higashi-Kawasakisaki town, n = 12 12 for for Suzukaze Suzukaze town). town). 4. Lessons for Japanese Disaster Risk Management 4. Lessons for Japanese Disaster Risk Management The field surveys allowed some important lessons to be learnt from the event, which should The field surveys allowed some important lessons to be learnt from the event, which should inform future disaster risk management in Japan. Although information about the overall damage inform future disaster risk management in Japan. Although information about the overall damage and inundation heights along Osaka Bay are provided by Mori et al. [9], it is still important to and inundation heights along Osaka Bay are provided by Mori et al. [9], it is still important to compare the inundation that took place in the various areas with those predicted by local authorities compare the inundation that took place in the various areas with those predicted by local authorities through hazard maps. A Committee for Measures against Storm Surge in Osaka Bay [21] simulated through hazard maps. A Committee for Measures against Storm Surge in Osaka Bay [21] simulated three scenarios for storm surge (Scenarios 1, 2 and 3), and provided the expected inundation maps three scenarios for storm surge (Scenarios 1, 2 and 3), and provided the expected inundation maps for each of these scenarios. In Scenario 1, they assumed that a typhoon with a central pressure for each of these scenarios. In Scenario 1, they assumed that a typhoon with a central pressure of 930 of 930 hPa at the time of the landfall (which would be as strong as the Isewan Typhoon (1959), hPa at the time of the landfall (which would be as strong as the Isewan Typhoon (1959), and stronger and stronger than Typhoon Jebi by 20 hPa), would move along the same route as the Muroto Typhoon than Typhoon Jebi by 20 hPa), would move along the same route as the Muroto Typhoon (1934) (See (1934) (See Figure1). In this scenario, they also assumed that their coastal defenses (e.g., water gate, Figure 1). In this scenario, they also assumed that their coastal defenses (e.g., water gate, seawall) seawall) would be damaged due to the collision force by drifted ships and not work properly during would be damaged due to the collision force by drifted ships and not work properly during such an such an event (e.g., water gate cannot be closed). In Scenarios 2 and 3, they assumed a stronger typhoon, event (e.g., water gate cannot be closed). In Scenarios 2 and 3, they assumed a stronger typhoon, having a central pressure of 910 hPa at the time of landfall, and shifted the course of the typhoon having a central pressure of 910 hPa at the time of landfall, and shifted the course of the typhoon west by 40 km from that in Scenario 1. The coastal defenses were assumed to work properly in west by 40 km from that in Scenario 1. The coastal defenses were assumed to work properly in Scenario 2 (no damage due to a collision by drifted ships), whereas they were assumed not to in Scenario 2 (no damage due to a collision by drifted ships), whereas they were assumed not to in Scenario 3. Higashi-Kawasaki town, Mikageishi town and Fukaehama town were predicted to be Scenario 3. Higashi-Kawasaki town, Mikageishi town and Fukaehama town were predicted to be flooded by all scenarios. However, the maps do not indicate that Suzukaze town was at risk of flooded by all scenarios. However, the maps do not indicate that Suzukaze town was at risk of being being flooded in Scenario 1, even though the typhoon modelled was stronger than Typhoon Jebi in flooded in Scenario 1, even though the typhoon modelled was stronger than Typhoon Jebi in terms terms of central pressure at the time of the landfall. A storm surge and a tsunami hazard map for of central pressure at the time of the landfall. A storm surge and a tsunami hazard map for Suzukaze Suzukaze town are also provided by Hyogo Prefecture [18]. The storm surge hazard map was based town are also provided by Hyogo Prefecture [18]. The storm surge hazard map was based on a on a simulation of (1961), shifting the course of the historical typhoon to the west simulation of typhoon Nancy (1961), shifting the course of the historical typhoon to the west by 10°. by 10◦. It should be noted that the map clearly states that it does not include the possibility of river It should be noted that the map clearly states that it does not include the possibility of river flooding flooding and wave overtopping. The tsunami hazard map was based on a tsunami simulation of and wave overtopping. The tsunami hazard map was based on a tsunami simulation of the Nankai the Nankai trough earthquake [22]. Neither the storm surge nor the tsunami hazard maps indicated trough earthquake [22]. Neither the storm surge nor the tsunami hazard maps indicated there was a there was a risk of flooding for Suzukaze town (for the other three areas analyzed in the present study, risk of flooding for Suzukaze town (for the other three areas analyzed in the present study, this risk this risk was predicted to some extent). Thus, it was clearly more difficult for residents at Suzukaze was predicted to some extent). Thus, it was clearly more difficult for residents at Suzukaze town to town to realize that they were actually at risk of being flooded. Indeed, the questionnaire survey realize that they were actually at risk of being flooded. Indeed, the questionnaire survey revealed revealed that most of the residents at Suzukaze town did not think that a storm surge could overcome that most of the residents at Suzukaze town did not think that a storm surge could overcome the the defenses in their area, and did not evacuate to higher ground. In that regard, it would be rational defenses in their area, and did not evacuate to higher ground. In that regard, it would be rational to reconsider re-evaluating risk potentials in not only Suzukaze town, but perhaps also in other areas that have been previously considered to have minimum risks. The possible wave overtopping at

Geosciences 2018, 8, 412 16 of 19 to reconsider re-evaluating risk potentials in not only Suzukaze town, but perhaps also in other areas that have been previously considered to have minimum risks. The possible wave overtopping at Suzukaze has introduced a degree of uncertainty in currently available storm surge hazard maps around Osaka Bay. Reassessing the vulnerability and risk management at the local and regional scale would undoubtedly help in addressing the concerns and uncertainty left by Typhoon Jebi. Generally, a storm surge hazard map is created by simulating several typhoon scenarios [23]. In such simulations, the pressure distribution of the typhoon and its moving speed are typically modelled in a relatively simplistic way (e.g., using Myers equation [24] to reproduce the pressure distribution). However, the actual storm surge height at a given location is sensitive to local geographic and bathymetric conditions, and the exact wind conditions at an area during the passage of a typhoon. Thus, the actual storm surge height at a given point of interest could be higher than that simulated one. In addition, when elaborating a storm surge hazard map, the effects of overtopping waves are seldom included. As shown by previous storm surge events [25–27], the extent of the damage to human being depends on the level of people’s awareness and preparedness. Considering this, it is important to make coastal residents aware that inundation could occur even if they are outside of the predicted storm surge inundation area. Especially, a newer community created on reclaimed land along the coast, such as Suzukaze town, has less experience with coastal hazards, as there is no collective memory of previous disaster events (see Esteban et al. [28]). Thus, it is imperative for disaster risk managers and local authorities to make them aware of risks related to natural hazards, and evacuate to areas of higher elevation whenever a strong typhoon approaches. Another important lesson from this event is the necessity of considering the effects of drifting objects. During the event, many containers were displaced from ports, with the authors recording the location of 14 at the waterfront of Suzukaze town. This problem has actually been observed in other past events [29–32]. For example, during the 2011 Tohoku Earthquake and Tsunami, many containers were moved by the strong tsunami flows [30]. Such problems were also recorded for the case of ’s storm surge in 2005 [32]. For the case of Suzukaze town, the maximum inundation depth was found to be 64 cm, which was not high enough to destroy the houses in the area [33]. However, if containers had managed to overcome the embankment in front of the area, the forces exerted on the houses could have damaged many of them. Many researchers have conducted hydraulic physical model tests and confirmed that the magnitude of a tsunami force would be significantly increased due to the presence of debris (in this sense, a weak tsunami force and a storm surge can be somewhat similar [34–36]). In addition, it takes considerable effort to collect all the drifted containers (in fact, Kobe city spent 10 day to collect all of them). Thus, it is necessary to give some further consideration on how to predict the location of drifted containers during a severe coastal flooding event. Some numerical simulation models to predict the movement of debris under tsunami flows have been proposed [37–39]. Although most of these types of models were validated by comparison with hydraulic physical model tests, a prolonged period of water surface elevation such as tsunami or a storm surge are difficult to accurately reproduce at the experimental scale. The movement of large vessels under strong tsunami flows were recorded during the 2011 Tohoku Earthquake and Tsunami, using Automatic Identification System (AIS) [40]. Naito et al. [30] investigated the positions of drifted containers by using satellite images taken at several areas affected by the 2011 event. However, to the authors’ knowledge, detailed information about the location of the actual containers displaced has never been provided. In that sense, the information provided in the present work should be useful to validate future simulation models of container displacement.

5. Conclusions In the present work, the authors surveyed the coastal flooding that took place as a result of Typhoon Jebi in Japan in 2018. It became clear that some coastal residential areas had been flooded due to a storm surge, despite the dyke protecting them being substantially higher than the predicted Geosciences 2018, 8, 412 17 of 19 and measured storm surge levels at nearby tidal stations. For example, inundation depths ranging from 0.18 m to 0.64 m were measured at Suzukaze town. This indicates that some interesting geographical, bathymetric of wind factors played a part in increasing the height of the water levels at Suzukaze town, which was considered to be a minimum risk area. This storm was described as the worst in 25 years, and it would thus appear surprising that flooding would take place as a result of it. The current hypothesis regarding the reasons for the sea water flooding at Suzukaze town is that it was caused by wave overtopping. Such failures of the coastal defenses, albeit localized, highlight the need for further research into the detailed behavior of storm surges along the complex Japanese coastline and the need to reassess what are currently considered minimum risk areas, in order to reduce a degree of uncertainty left after the passage of Typhoon Jebi. The authors also interviewed the residents of the areas flooded, and carried out a questionnaire survey of local residents, though the number of respondents was limited to 17. Through this it became clear that residents of newly reclaimed areas had a poor level of awareness about the potential dangers of a storm surge (e.g., none of the 12 respondents in Suzukaze town evacuated during the event), partially because they had not experienced any such events during their lifetimes. The failure of local authorities to issue evacuation orders well in advance of the event, and the lack of evacuation to higher grounds (local residents mostly chose to evacuate vertically, though their houses were comparatively weak constructions, only 2 or 3 floors high) are potentially hazardous types of behavior. Thus, it would appear imperative that local authorities should emphasize the need for proper evacuation (either to higher grounds or strong tall concrete buildings) when strong typhoons approach. The present research highlights how, although relatively well prepared, there is still much that Japanese local authorities need to learn with regards to coastal risk management. Given that the strength of typhoons could increase in the future as a consequence of climate change, it is necessary that measures are put in place to increase the resilience of coastal communities.

Author Contributions: All authors joined the field survey. T.S., M.E., R.N., M.M., T.O.K. and J.J.V. conducted a survey to investigate inundation heights in the study areas. T.T. and Y.N. recorded the location of displaced containers in Suzukaze town. T.T., H.I. and F.N. carried out a questionnaire survey of local residents. T.T., M.M. and M.E. contributed to the writing of the manuscript, analysis, and visualization. R.N., T.O.K., H.I., J.J.V., Y.N. and F.N. contributed to the editing of manuscript and analysis. T.S. supervised the team and reviewed the manuscript. Funding: This research was partly funded by Penta-Ocean Construction Co., Ltd. and by New CC Construction Consultants Co., Ltd. Acknowledgments: The present work was performed as a part of activities of Research Institute of Sustainable Future Society, Waseda Research Institute for Science and Engineering, Waseda University. Conflicts of Interest: The authors declare no conflict of interest.

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