沿岸センター研究論文集

No.5（2005）

A Study on Future Perspective of Disaster-Prevention Studies Obtained through the Inspectionof 2004 Indian Ocean Tsunami-Devastated Sites in Thailand
SHISHIDO Tatsuyuki*，KITAMURA Michio*，GOTOH Katsushi**，SUKEYASU Yoshiki***and YAMAMOTO Chuji***** Coastal Development Institute of Technology** Ohmotogumi, Co., Ltd.
*** Hitachi Zosen Corporation**** Japan Meteorological Business Support CenterTsunami, which was exemplified by 2004 Indian Ocean tsunami, notified the world of its threat, signifying quite a few unresolved
issues on tsunami studies. In order to acquire on-site information and detect clues to the unresolved issues, Coastal Development
Institute of Technology sent its own field survey teams to the tsunami-devastated sites of Thailand in March and April. This paper
presented summaries of survey outcomes obtained in March field trip.
Key Words: tsunami, field survey, earthquake, disaster, Thailand

1．Introduction
Coastal Development Institute of Technology (CDIT) has
been making disaster-prevention studies in coastal areas amongits main tasks. The importance of tsunami study is growing so asto reduce impacts owing to such earthquakes as Tokai,
Tonankai-Nankai and Miyagi. Occurring on December 26, 2004,
2004 Indian Ocean tsunami with Sumatra-Andaman earthquake
notified the world not only of the threat of tsunami but also theimportance of countermeasure to it. In order to incorporate
views concerning the tsunami into our research activities, whilecollecting data from several reports both by Japanese
government and Japan Society of Civil Engineering, CDIT sent
its own field survey squads to the tsunami-devastated sites inThailand. This report summarized the first phase field survey inthis March.

3．Purpose of Field Survey
CDIT’s “First-Phase squad for 2004 Indian Ocean Tsunami
survey”, composed of the authors of this paper, visited thedevastated sites in Phuket Island and Kao Lack beach of South
Thailand on March 13th and 14th to make its field studies onaftermaths owing to the tsunami. Surveyed spots are depicted inFig.1.

2．Outline of 2004 Indian Ocean tsunami
Sumatra-Andaman earthquake, magnitude of which isestimated at 9.0 with its focal region of 800km, originated in the
Indian Ocean off the west coast of North Sumatra at 07:58:53
local time on December 26, triggering massive tsunamis thatobliterated seaside communities in a dozen countries, especiallyinflicting catastrophic damages there. The first tsunami arrived
in South Thailand and Sri Lanka two hours after the seismic
strike. Even in the east coast of Africa 5000 kilometer off theseismic center, the tsunami was subsequently detected ten hours
later. In more than 20 spots at Banda Aceh of North Sumatra,
over 20-meter high tsunamis, the maximum height of whichwas 34.9 meters, were observed. In other areas, reported aresuch cases as over 10-meter high tsunamis in Kao LAK beachof South Thailand, those ranging from 5 to 6 meters in Phuket
Island and so forth. Worldwide efforts were made for recovering
devastated sites where approximately 300,000 people werekilled, however there still remain yet-to-be-revived areas eventwo months after the catastrophe.

Fig.1 Surveyed Spots and Measured Tsunami Heights
The above figure was excerpted from an internet website,
http://www.drs.dpri.kyoto-u.ac.jp/sumatra/thailand/phuket_survey.html, of Disaster Prevention Research Institute, Kyoto
University.
On 13th, the authors visited beaches of Patong, Kamala,Karon, Katanoi, Katayai and Naihan, all of which are locatedin east coast of Phuket Island, to investigate their afflictions and－ 109 －沿岸センター研究論文集

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rehabilitations. On 14th, we made a field survey on theplanting density and damages in Khuk Khak beach of Kao
Lack. These surveys were practiced with researchers bothfrom Independent Administrative Institution, Port and Airport
Research Institute and from Prince of Songkla University.

4．Aftermaths of Devastated Sites
Damages in Kamala beach and Khuk Khak beach of Kao
Lack had remained unchanged for two months when we visited.
Kamala Beach in Phuket Island
Kamala beach, located in the center of Phuket Island, is
2000-meter long seashore, ranging in its width from 30 meters
to 50 meters. Several Pine trees were found there. The verticalinterval between its seashore and ground was approximately one
meter and that between its sea and ground was approximately
two meters. There were located hotels, roads, pathways,
buildings and resort houses, mutual positions of which aredepicted in Fig.2, behind surveyed spots.

Fig.3 A Resort House Damaged in its Front

Fig.4 A Pathway Damaged by the Suction of its Base Sand

Resort Houses
TreesHotels, fronts of which are open for the sea, also received
severe damages, their recovery works going under way. It isconsidered that, judging from the discoloration of its nearby
Palm trees’ leaves, the police station, located near the coast roadin the north of hotels, was struck by 4 to 5-meter high tsunami,
remaining intact due to its firm structure depicted in Fig.5. In
contrast, disastrous damages of wooden houses in further inlandarea, depicted in Fig.6, are characterized by missing walls intheir first floors, and corrosions of their foundations. It is
presumed that these damages were caused by the passage ofhighly energized tsunami.

Houses with Corroded Foundations

Sea
Wooden Houses with Only Columns
Remaining in Their First Floor
Pathway
Police Station
PlantsHotelsFig.2 Air View of Surveyed Spots in Kamala Beach
Note: Precise distances among facilities are not shown up above.
A resort house owner who experienced the tsunami said thathe could escape from the first wave, because its height was
below his body. The second wave 15 minutes later, however,
was high enough to be over the roof of his house. While finding
works for rehabilitation and rubble removal of some damaged
facilities, we could also find many damages in other facilities.
Impacts on facilities due to the tsunami can be characterized bycollapses of their seaside walls, depicted in Fig.3, excepting theircolumns and base structures. These impacts are reduced
according to the distance from the coast. Dwellings in further
inland areas, however, also suffered from noted damages, whichwere supposedly induced by the invasion of the tsunami into
intervals between resort houses. Most of pathways weresignificantly inflicted; especially some of their surfaces weredepressed by the outflow of their sand bases. Such damages,depicted in Fig.4, were notable in their seasides with no plants.

Fig.5 Unaffected Building of Police Station

Fig.6 A Wooden House Sustaining Columns in its First Floor－ 110 －

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Khuk Khak Beach in Khao Lak
We made surveys on damages around Theptharo Lagoon
Beach Resort in Khuk Khak beach of Central Kao Lak. There
were doted cottages, each of which are 10 meters wide, 15
meters deep and 4 meters high, along the coastline of lagoon
shaped as sandpit. Since simple structures were installed incottages, all of them suffered from such severe damages as
disconnections between their superstructures and substructures,
fractures of their members, inclinations or collapses,submersions under the lagoon and so on. We founddisappearances of their front walls or collapses of their column
in half of cottages. As for cottages near the sea, their damages,
which are noted as complete collapses of their structures or thoseof their superstructures such as columns and walls, were moresignificant than cottages along the lagoon. Two cottages locatedfarthest from the coast, however, remained comparatively intact,
receiving small injuries only in their walls. Besides, traits ofcorrosion were also found in footings of many cottages. Most ofpile foundations that were installed in the lagoon remained
structurally sound. Many of newels on balconies, though they
are set in forefronts of cottages, remained undamaged.
Attentions should be paid to Fig.8 showing a damaged house,around which its back and forth walls facing the sea weremissed and rubbles of its 10-centimeter thick walls were
scattered around. In addition, several bicycles also lay broken
inland.
It is presumed that all aforementioned damages were also
caused by same phenomenon as that in Kamala beach.

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Fig.8 A House Damaged in its Seaside Wall
Survey on Planting Density
Planting density around Kao Lak Orchid Hotel was also
investigated. Fig.9 depicts a survey outcome obtained in thesouth of the hotel. A part of pine trees that were planted beforethe development of surveyed spot remained in the coast, and theforestations of palm trees were gridironed at 10-meter intervals
in approximately 100-meter wide inland zone. Trunk diametersof Palm trees were about one meter, and heights of them ranged
from 10 to 30 meters. In 10-meter upper part of most trees,
which were positioned in the third to the forth line of theplanting strip, their barks were peeled. Levels of their peelings
tended to be lower in accordance with the distance from thecoast.
It indicates that planting strip with its observed degree ofplanting density did not perform enough to weaken the strengthof the tsunami. Furthermore phenomena that roots of the trees
prevented the outflow of beach sand and the collapse of groundwere found not only in some spots but also in other beaches

Fig.7 Damaged Cottages
PalmTree: 100 cm DiameterofTrunk at its 1.0-meter.height.
PineTree: Cut down at its base.

Coast Line
Holding Pond

PineTree: 80 cm Diameter ofTrunk at its 1.0-meter.height.

Average Interval of Plants: 9.2 m

Average Interval of Plants: 13 m
53.0 m12.5 m127.8 m
8.5 ma) 200-meter South of Orchid Beach Resort
Fig.9 Survey Result of Planting Density－ 111 －b) Conditions of Palm Trees

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No.5（2005）

intervals of structures, plants and so on with its strong impetus.
Phenomena of such strikes and run-ups depended on
geographical and sites conditions.

（2）Collapses of Structures and Plants
Buildings closest to coasts suffered from severe damages.
While damages of bearing-wall structures were notable in theirseaside walls, those of wave-pervious structures such as column
structures were comparatively small. Furthermore rigidstructures lied durable. As for trees, although their barks facing
the sea were peeled, they remained intact.

（3）Characteristics of Ground Collapses
Fig.10 Corrosions at Bases of Trees
Other Beaches
Patong beach, the tsunami into which was reported
worldwide by the media, is one of typical beaches in west coastof Phuket Island. We found some damages such as breaches ofpavements in parking lots, corrosions of basements of trees andstructures, collapses of coastal facilities due to outflows offoundation grounds and so on. But these damages did not affectcivic life there any more. The beach was crowded with manyvisitors. Shops in the streets were also run as usual.
In Kalon beach, formed was the sandbank that is 4 to 5-meterhigh and approximately 10-meter wide. No particular damages
were seen behind its back. In Katayai beach, rehabilitation
works for damaged walls of hotels went under way. Some
depressions due to outflows of sand basements were found there.
In Katanoi beach, seen were such trails as the collapse of its
riverbank, accumulated dusts in the coast and so on. In Naihan
beach with large level gaps between its sea and ground, few
tsunami trails were seen. There were many tourists, which aredepicted in Fig.11.

While surroundings of foundation structures were deeply
corroded by the tsunami, roots of trees were presumed to beeffective in preventing both outflows of sand basements andcollapses of grounds.
It is generally known that hazard map can be an efficient tool
to predict impacts due to tsunami. As this field survey clarified
that impact due to tsunami could depend on geographical andland use conditions, it indicated the importance of hazard mapthat can present reliable information to reduce the impact due totsunami. It is considered that issues to be resolved in furtherstudies should be as follows: clarifications of fluid and impulsive
forces of tsunami, the mechanism of tsunami passage between
structures; the evaluation of structural performance against thestrike of tsunami; the improvement of structural durability ofcoastal facilities. In addition, even though enough data on thecorrelation between planting density and tsunami could not beobtained, further research between them will continue to be oneof the most important themes on tsunami studies.

6．Acknowledgments
Sumatra-Andaman earthquake and 2004 Indian Ocean
tsunami killed quite a few people. Through this field survey, we
firmly recognized the emergency to prevent such tragedies
forever. It is hoped that this paper can be helpful in presenting
one of the useful references not only for CDIT but also thosewhom it may concern. In conducting this field survey, we would
like to express our sincere appreciations to Dr. Tetsuya Hiraishi,
Head of Wave Laboratory at Independent Administrative
Institute of Port and Airport Research Institute for his kind leads
and advices. We strongly recommend that all readers shall refer
to “First-Phase Report on Field Survey of 2004 Indian OceanTsunami” published by CDIT on May 2005, for more
information.

Fig.11 Kata Yai Beach Crowded with Visitors

5．Conclusions
It is one of the most basic strategies against tsunami to predict
their impacts. Based on this field survey, our summaries
concerning on-site statuses during the tsunami strike are as
follows:（1）Hydraulic Traits of the Tsunami
The tsunami characterized by its significant fluid force madeimpulsive strikes on damaged structures, passing through－ 112 －