TSUNAMI DAMAGE ASSESSMENT
In order to protect life and property from the damage caused
by a theoretical tsunami, the type and scale of potential damage must
first be estimated.
This estimate is derived from evaluations of damage caused by
past tsunamis, along with current land use, population, and
agglomeration of buildings and industries in the at-risk community.
These factors are then compared to the estimate of a theoretical
tsunami’s inundation (calculated from the numerical analysis of
approximate water height) and existing shore protection structures,
the results of which can effectively indicate the extent of danger.
Nevertheless, there will still be considerable uncertainty in
regard to the secondary damage that tsunamis cause, namely floating
debris, fires and damage by chemicals, such as oil. With this in mind,
the estimate itself should only be used as a bare outline of all them
potential hazards.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
Great East Japan Earthquake
and tsunami
United Nations Environment Programme. Great East Japan Earthquake and
tsunami. [2013 02 20]. Available on the Internet:
<http://www.unep.org/tsunami/>.
Hazardous Materials
Hazardous materials, such as spills of oil and gasoline, cause secondary
damage during a tsunami. Great care should therefore be taken to ensure they are
protected and safely stored.
Storage tanks should be buried and steps to prevent spills should be taken in
order to make them less susceptible to tsunamis. Another measure is to store such
materials in tsunami-proofed warehouses, but volume and size are often in excess of the
capacity available, in which case little can be done. Improvements to timber yards are an
immediate concern.
Tsunami waves often turn timber, fishing boats and equipment into projectiles.
They are carried on the waves as they surge inland and easily destroy embankments,
bridges, facilities and houses.
The safety of residents is of paramount importance. Sufficient supplies for the
rapid recovery of spills and/or extinguishing fires should be stored and ready and
procedures carefully planned. Management and public authorities in charge of hazard
mitigation should cooperate during the design and construction phase of such facilities
to create a functioning system for such emergencies
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
On 11 March 2011, a 9.0 magnitude earthquake off the
north-eastern coast of Japan – the strongest ever recorded in the
country – triggered a tsunami up to 30 metres high that washed
up to 5 kilometres inland. It resulted in massive loss of life,
environmental devastation and infrastructural damage. The
disaster also damaged several nuclear power plants, leading to
serious risks of contamination from radioactive releases.
United Nations Environment Programme. Great East Japan Earthquake and tsunami. [2013 02 20]. Available on the Internet:
<http://www.unep.org/tsunami/>.
IMPACTS OF RECENT TSUNAMIS &
THEIR CHARACTERISTICS (1)
The majority of tsunamis are thought to be generated by earthquakes below
the sea floor. Importantly however, they may also be generated by volcanic eruptions,
underwater landslides, asteroid/comet impacts in to the ocean and occasionally,
meteorological conditions. However, things are not quite that simple, the Pacific also
experiences unusually large tsunamis associated with poorly understood processes
operating at subduction zones. These include “tsunami earthquakes” where larger
than expected tsunamis are generated by “slow” earthquakes and by earthquakes that
simultaneously generate submarine landslides.
In September 2009, yet another unexpectedly large tsunami resulting from
an unusual earthquake event occurred in the South Pacific. In essence, we are
continuing to experience larger tsunamis than anticipated by current numerical
modelling scenarios. This is of enormous concern for the Pacific (and PICTs) where
attention has largely been focussed on subduction zone events with little or no
consideration given to regional tectonic and submarine landslide sources that can be
equally important for individual PICTs. This is significant because, local and regionally
generated events pose the greatest challenge for effecting warning alerts and ensuring
adequate community response (e.g. evacuation).
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
Available on the Internet: <http://wwwwds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2011/07/22/000356161_20110722030203/Rendered/PD
Post-disaster waste management
Along with the unresolved situation at the Fukushima Daiichi power
plant and pressing humanitarian issues linked to the large number of
displaced and dispossessed, the management of the massive amounts of
debris generated by the earthquake and tsunami has been identified by the
Government of Japa as an immediate challenge.
The total amount of waste has been estimated to be between 80 and
200 million tons – comparable in size to the waste generated by Hurricane
Katrina, which cost over USD 3.2 billion to clean up. The shortage of land will
further escalate the cost of post-disaster waste management in Japan.
United Nations Environment Programme. Great East Japan Earthquake and tsunami. [2013 02 20]. Available on the Internet:
<http://www.unep.org/tsunami/>.
CHALLENGES INIDENTIFYING, ASSESSING & MONI
TORING TSUNAMI RISKS (1)
There are a number of important challenges that exist in relation to identifying, assessing and monitoring the risk
from tsunamis. We discuss these in relation to each element of the risk management process identified in the previous section.
The first point is our limited understanding of tsunami sources – the hazard assessment. Prior to the 2004 Indian Ocean disaster,
few (if any) had imagined the possibility of extremely large (Magnitude 9+) earthquakes along the Sumatra subduction zone. The
geophysical constraints of the subduction system and its capacity to generate such large events were not fully recognised.
In many ways this problem hinges on a key issue related to assessing the tsunami hazard for any region – a lack of
context. Until we have a better understanding of how subduction zone geology/geophysics constrains maximum earthquake size,
or we can be sure that our knowledge of the tsunami record is complete, we must assume that any subduction zone can generate
a large tsunamigenic earthquake. We should therefore strive to improve understanding of past (historic and prehistoric) events in
order to better understand our future.
One recently developed method to undertake quantitative tsunami hazard assessment is the Probabilistic Tsunami
Hazard Assessment (PTHA) that is based on numerical simulations of what are believed to be ‘plausible’ tsunami scenarios. Such
an assessment has been conducted for SOPAC (Secretariat of the Pacific Community, Applied Geoscience and Technology Division)
member countries. This approach accounts for large earthquake occurrence on all subduction zones, even those that are not
known to have generated large tsunamis. However, these deal almost exclusively with reasonably simple subduction zone source
scenarios using historical data as their primary contextual source. The nature and extent of larger events are in general
extrapolated from these historical data coupled with a rudimentary understanding of the geophysical properties of the fault zone
in question. Scant consideration is given to Traditional Environmental Knowledge (TEK) about past events and geological data
concerning prehistoric tsunamis.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
Available on the Internet: <http://wwwwds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2011/07/22/000356161_20110722030203/Rendered/PD
CHALLENGES INIDENTIFYING, ASSESSING & MONI
TORING TSUNAMI RISKS (1)
There are a number of important challenges that exist in relation to identifying, assessing and monitoring the risk
from tsunamis. We discuss these in relation to each element of the risk management process identified in the previous section.
The first point is our limited understanding of tsunami sources – the hazard assessment. Prior to the 2004 Indian Ocean disaster,
few (if any) had imagined the possibility of extremely large (Magnitude 9+) earthquakes along the Sumatra subduction zone. The
geophysical constraints of the subduction system and its capacity to generate such large events were not fully recognised.
In many ways this problem hinges on a key issue related to assessing the tsunami hazard for any region – a lack of
context. Until we have a better understanding of how subduction zone geology/geophysics constrains maximum earthquake size,
or we can be sure that our knowledge of the tsunami record is complete, we must assume that any subduction zone can generate
a large tsunamigenic earthquake. We should therefore strive to improve understanding of past (historic and prehistoric) events in
order to better understand our future.
One recently developed method to undertake quantitative tsunami hazard assessment is the Probabilistic Tsunami
Hazard Assessment (PTHA) that is based on numerical simulations of what are believed to be ‘plausible’ tsunami scenarios. Such
an assessment has been conducted for SOPAC (Secretariat of the Pacific Community, Applied Geoscience and Technology Division)
member countries. This approach accounts for large earthquake occurrence on all subduction zones, even those that are not
known to have generated large tsunamis. However, these deal almost exclusively with reasonably simple subduction zone source
scenarios using historical data as their primary contextual source. The nature and extent of larger events are in general
extrapolated from these historical data coupled with a rudimentary understanding of the geophysical properties of the fault zone
in question. Scant consideration is given to Traditional Environmental Knowledge (TEK) about past events and geological data
concerning prehistoric tsunamis.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
Available on the Internet: <http://wwwwds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2011/07/22/000356161_20110722030203/Rendered/PD
THE BASIS OF TSUNAMI READINESS
In assessing the risk, namely, configuring the
magnitude of a theoretical tsunami and identifying
vulnerable areas, officials should make projections based
on the largest tsunami possible. Using this as a
hypothetical benchmark fosters the maximum safety for
planning purposes.
Recent scientific research on earthquakes
generating tsunamis along high-risk coasts and data from
the largest tsunamis (for example, water mark heights for
recent and geological evidence for older ones) provide us
with scientific evidence, sometimes very accurate. This
information enables us to make projections and assess
the potential threat for tsunamis in a given area.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
Disasters and Disaster Risk are a Development
Challenge (2)
Communities will have to adapt even more to these stressful environmental
conditions, through disaster risk reduction and resilience building measures. This will especially
impact on least-developed countries and Small Island Developing States. While all countries are
vulnerable (as demonstrated by the Great East Japan earthquake and tsunami) the impact
disasters have on Least Developed Countries and Small Island Developing States is perhaps the
most challenging. For these States, disaster events have a significant impact on, or in some cases
completely destroy, development gains built up over decades. Hurricane Ivan (2004) cost Grenada
over 200 per cent of GDP. The earthquake in Haiti (2010) is estimated to have exceeded 15 per
cent of GDP or 120 per cent of GDP when total damages and losses are included. In larger LDC
economies, such as Bangladesh or Mozambique, the loss of 3 to 5 per cent of GDP, due to
disasters, every five to ten years has a cumulative impact on development.
The risk of losing wealth in weather-related disasters is now outstripping the rate at
which the wealth itself is being created. Since 1980 the risk of economic loss due to floods has
increased by over 160 per cent and to tropical cyclones by 265 per cent in OECD countries.
Economic loss risk to floods and cyclones in the OECD is growing faster than Gross Domestic
Product (GDP) per capita. For instance, the Great East Japan earthquake and tsunami caused an
estimated 1 per cent reduction in Japan’s GDP. The 2011 floods in Thailand similarly led to an
estimated 2.5 per cent drop in global industrial production and caused damages of USD 40 billion.
UNISDR, WMO. 2012. Thematic Think Piece. Disaster risk and resilience. Un System Tast Team on the POST-2015 Un Development Agenda.
Available on the Internet: <http://www.un.org/millenniumgoals/pdf/Think%20Pieces/3_disaster_risk_resilience.pdf>.
THE GENERAL CONTEXT (1)
Tsunamis can be devastating. The 2004 Indian Ocean and 2011
Tōhoku disasters provide frightening examples of the power of tsunamis. The
Pacific has long been recognised as a place where tsunamis occur - the
“Pacific Ring of Fire” (PRF) contains regions of volcanoes and large
earthquakes associated with tectonic plate motions that are ideal breeding
grounds for tsunamis.
The Pacific Ocean covers an area of 30 million km2. Some 22 Pacific
Island countries and territories (PICTs) are otted throughout the Pacific and
are vulnerable to varying degrees, to the effects of tsunamis generated
locally, regionally and distantly.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
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Environmental impacts and risks
Other environmental issues requiring attention during the recovery phase
could include:
Soil and groundwater: When seawater penetrates far inland, land salinity (and hence agricultural
productivity) and shallow groundwater quality (if used for drinking or irrigation) can be affected;
De-silting of coastal canals: Coastal waterways were fully silted by the tsunami and will need to be drained
in order to become operational;
Water supply and sewage networks: Damage to urban water supply and sewage networks can result in
cross contamination, leading to health impacts for the population;
Coastal ecosystems: Coastal habitats and ecosystems can be destroyed, with implications for livelihoods;
and
Environmental risks of reconstruction: Reconstruction operations can have a significant environmental
footprint, particularly if environmental considerations are not taken into account in planning and managing
operations such as waste disposal and clean-up.
Immediately after the earthquake and tsunami, UNEP's Executive Director wrote to
Japan's Prime Minister and Environment Minister respectively to express his
condolences and offer UNEP's assistance and expertise. UNEP has significant first-hand
experience in managing the environmental impacts of major disasters and stands ready
to assist the Government and people of Japan, if requested.
United Nations Environment Programme. Great East Japan Earthquake and tsunami. [2013 02 20]. Available on the Internet:
<http://www.unep.org/tsunami/>.
LOCAL PLANNING
Tsunami preparedness is just one part of a comprehensive plan
covering a broad range of possible local damage, including that caused by
earthquakes, wind and rain, storm surges and volcanic eruptions. When a
tsunami is generated in a local area, there is little or no warning time
before it strikes. Consequently, the building blocks of tsunami readiness
are advance planning and the establishment of evacuation areas,
maintenance of evacuation routes, communication systems and the rapid
dissemination of accurate information.
The two key areas that officials need to set up are:
• URBAN PLANNING to strengthen at-risk communities’ preparedness,
including zoning restrictions, relocation to higher ground, renovation
and reconstruction of dilapidated structures;
• EMERGENCY READINESS forming the organizational structure and
activity behind tsunami readiness, such as warning systems,
establishing evacuation zones and routes, public educational
programmes and protection of the fishing industry.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
Results
Our quantitative survey conducted during the same time period as this qualitative
study revealed that the overall prevalence of symptoms of post-traumatic stress in
surveyed villages nine months after the tsunami was 6.4%, considerably lower than
that predicted immediately after the tsunami, and largely confined to those who had
lost loved ones in the tsunami. Details of this survey will be published elsewhere.
(Rajkumar et al. 2008)
Reconstructive and resettlement activities had not progressed as expected and the
majority of participants were still living in shelters. Aid agencies and health workers
were still present and active in the area, though less numerous than in the immediate
aftermath of the tsunami. Though some fishermen had resumed normal fishing
activities, political processes connected with compensation claims had prevented
widespread resumption of commercial fishing. Rumors about earthquakes and
impending tsunamis were rife and facilitated by reports in the press and through local
radio and television programs. (Rajkumar et al. 2008)
Rajkumar, A. P., Premkumar, T. S., Tharyan, P. Coping with the Asian tsunami: Perspectives from Tamil Nadu,
India on the determinants of resilience in the face of adversity. Social Science & Medicine 67 (5), 2008, pp. 844853.
WHAT DOES ‘TSUNAMI RISK MANAGEMENT’
INVOLVE? (2)
Clearly, experts from different discipline fields will be involved in generating
data associated with each step of this process. For example, generally speaking, earth
scientists are involved in the identification and characterisation of the tsunami hazard
(from not only earthquakes but all possible tsunamigenic sources). Numerical modellers,
oceanographers and coastal engineers will model the tsunami from source to
inundation. Social and human scientists and engineers will work to evaluate exposure
and vulnerability of relevant people, infrastructure and assets, and a range of experts
such as risk managers, engineers, social scientists, economists, geographers, etc. might
be involved in the quantification of the probable maximum loss (PML) associated with
the scenario. Lastly, risk managers have the task of integrating all these datasets and
decision makers determine how best to mitigate the risk identified. All this should
happen and the risk management actions should be in place before the next tsunami
occurs.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
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IMPACTS OF RECENT TSUNAMIS &
THEIR CHARACTERISTICS (2)
It is not the purpose of this Knowledge Note to provide a comprehensive analysis of the impacts and effects of
tsunamis of various magnitudes. However, in common with other types of natural hazards, tsunamis can cause extensive loss of
life and injuries to survivors. Tsunamis destroy and damage public and private coastal infrastructure, lifelines, critical assets and
infrastructure, agricultural systems and produce, transport and communication networks, natural ecosystems and the goods and
services those systems provide. Major tsunamis can lead to significant economic losses with recovery often counted in years to
decades. Even then, a return to economic growth does not compensate for the direct human and economic loss caused by the
event.
In the case of the 2011 Great East Japan Earthquake and Tsunami, the final toll will be immense. The number of
dead and missing exceeds 23,000 and economists have estimated the monetary loss at 16-25 trillion yen (US$198-310 billion),
about 3-5% of Japanese GDP and the effects of the Fukushima Daiichi nuclear plant remain unclear. The take home message from
this event is that even for the most well prepared Pacific country for tsunamis, it is impossible to prevent disaster completely and
huge damage was occurred although preparedness mitigated losses dramatically.
For PICTs such as Samoa, even a moderate event such as the 2009 South Pacific tsunami caused by an magnitude
8.1 earthquake was its worst natural disaster in at least half a century with nearly 150 dead and 2.5% of the population left
homeless. The final physical damage repair bill is expected to be around US$ 85 million (14% of GDP). However, when the
additional costs of maintaining basic social services and safety nets for the affected population and the costs for investing in
disaster risk reduction during the reconstruction process are considered, total economic cost is equal to about 21% of GDP over
the next three to four years.
It is also important to remember that tsunamis do not respect geographic boundaries and may cause losses across
entire (small) nations or the coastal zones of several countries simultaneously. Impacts and effects often ‘ripple’ out across
connected socio-economic and human-environment systems and transcend scales from the local to the global. For example, the
2009 South Pacific tsunami affected Samoa, American Samoa, Tonga and even caused damage as far away as the Wallis and
Futuna archipelago.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
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Main and local roads
• Main roads, such as national and prefectural routes, are critical as supply
routes during an emergency. As much as possible, their passage through
hazardous areas should be avoided; if this is impossible, roads must be
fortified against earthquakes and flooding. In extreme cases where main
roads are inaccessible during a tsunami, an alternative network of detours
must also be built and fortified in order to be in place and ready for
emergency transportation.
• Development tends to occur along main roads. Main roads in safe areas
therefore serve as an inducement to safe land usage. In cases where
elevated roads and heavy traffic cross coastal areas, alternative evacuation
route measures must be in place.
• Local roads also need to be fortified in order to serve as escape routes. The
construction of direct routes linking ports to safe residential areas located
further inland on higher ground is key to promoting safe land use.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
DEFENCE STRUCTURES
Defence structures reduce the damaging effects of tsunamis. They
include:
• Tsunami control forest belts;
• Tsunami-resistant buildings;
• Others (sea walls, tsunami breakwaters, tsunami tidegates, river
dikes, etc.).
Tsunami breakwaters and tsunami-resistant buildings are based on the
premise that the tsunami will undoubtedly breach existing sea
barriers. Their construction largely depends on civil planning, so they
are mentioned here as reference points. They can be effective by
blocking floating debris. Exactly how effective they are, however, is
difficult to quantify. If the tsunami runup depth is over four metres,
these defence structures have practically no beneficial effect.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
GOOD PRACTICE CASES (1)
There is no single example of comprehensive good practice. However, elements of good practice have been
adopted at international, national and local scales.
•
At the international and regional level, the UNESCO-IOC organised two Pacific-wide tsunami exercises in 2006 and 2008 to
encourage countries to prepare for the next tsunami. The next Exercise Pacific Wave (PacWave) 2011 will take place 9-10
November as a multi-scenario exercise to allow countries to practice responding to local and regional sourced tsunamis. For
PICTs, earthquake sources along the New Hebrides and/or the Philippines Trench can be used. PacWave, in which 44
countries participated, has been credited with saving lives in the 2009 South Pacific and 2010 Chilean tsunamis.
•
At a national scale, prior to the 2009 South Pacific tsunami, the Government of Samoa had developed an effective tsunami
early warning system, working with communities to raise public awareness and to practice evacuation drills and exercises.
These actions helped to save lives during the 2009 South Pacific tsunami since the population in many cases knew how to
respond. In American Samoa, September has been declared as ‘Disaster Awareness Month’. During this month in 2010, the
disaster management office conducted numerous outreach and training activities for government and nongovernment
agencies and schools, so that by the 29 September, many people knew about tsunamis.
•
At a local scale, the Island Council of Mangaia, Cook Islands, has passed a law stating that all new houses should be built
inland and uphill away from the coast, in part taking on-board the results of recent geological studies of past tsunamis on
the island27.
•
In Guam, American Samoa and the USA, there is a community-based programme called TsunamiReady which requires
communities to have redundant warning and alerting communications, tsunami response plans, tsunami hazard and
evacuation maps and signage, and active community and school education programmes. Similar efforts are in place in the
Philippines and being undertaken in Commonwealth Caribbean countries. These are the essential components of an
effective and successful end-to-end tsunami warning.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
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Railroads
Railroads need to be built in safe areas. When they traverse hazardous areas, they
should be properly fortified.
Transportation lines as dual levees
Some communities have the advantage of effectively having two levees by roads and
railways. In such cases, it is necessary to reinforce levees by elevating the roadbed and
stone or concrete pitching of the embankment. The gap in the junction between the
embankment filling and the wing wall of the concrete abutment is a weak point.
Lightweight beams on railroad bridges are also susceptible to damage by floating
debris.
Maintaining safety in ports and harbours
Being able to ship emergency supplies by sea is vital in areas that might be cut off from
emergency relief transport, such as those surrounded by mountains or peninsulas.
Accordingly, ports or harbours must be fortified against earthquakes so that they can be
used as supply, rescue and reconstruction centres. Attention must also be paid to the
safety of anchored and sailing vessels, as well as improving the function of the port and
harbour as a relief centre.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
Abstract
A tsunami, triggered by a massive undersea earthquake off Sumatra in Indonesia,
greatly devastated the lives, property and infrastructure of coastal communities in the coastal
states of India, Andaman and Nicobar Islands, Indonesia, Sri Lanka, Malaysia and Thailand. This
event attracted the attention of environmental managers at all levels, local, national, regional and
global. It also shifted the focus from the impact of human activities on the environment to the
impacts of natural hazards. (Sonak et al. 2008)
Recovery/reconstruction of these areas is highly challenging. A clear understanding of
the complex dynamics of the coast and the types of challenges faced by the several stakeholders
of the coast is required. Issues such as sustainability, equity and community participation assume
importance. The concept of ICZM (integrated coastal zone management) has been effectively
used in most parts of the world. This concept emphasizes the holistic assessment of the coast and
a multidisciplinary analysis using participatory processes. It integrates anthropocentric and ecocentric approaches. This paper documents several issues involved in the recovery of tsunamiaffected areas and recommends the application of the ICZM concept to the reconstruction
efforts. (Sonak et al. 2008)
Sonak, S., Pangam, P., Giriyan, A. Green reconstruction of the tsunami-affected areas in India using the
integrated coastal zone management concept. Journal of Environmental Management 89 (1), 2008, p.p. 14-23.
WARNING AND COMMUNICATION SYSTEM (1)
a)
Monitoring tsunamis.
In order to understand better the effects of various coastal features on
tsunamis and to improve readiness, one of the highest priorities
should be to develop and/or enhance a system for monitoring
tsunamis. The National Tsunami Warning Centre will make efforts to
strengthen tsunami monitoring. However, the magnitude of a tsunami
could be greater than that announced in some areas due to local
conditions. In addition, dedicated monitoring networks have different
configurations depending on the distance to tsunamigenic sources
from the actual risk area. In all cases the basic components of a
tsunami monitoring unit are the following:
• Seismic monitoring;
• Sea level monitoring;
• Updating redundant communications networks.
Intergovernmental Oceanographic Commission. TSUNAMI PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS. Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
TSUNAMI PREPAREDNESS
INFORMATION GUIDE FOR DISASTER
PLANNERS
Intergovernmental Oceanographic Commission. TSUNAMI
PREPAREDNESS. INFORMATION GUIDE FOR DISASTER PLANNERS.
Available on the Internet:
<http://unesdoc.unesco.org/images/0016/001600/160002e.pdf>.
CHALLENGES INIDENTIFYING, ASSESSING & MONI
TORING TSUNAMI RISKS (2)
While this approach offers a ‘general picture’ of the tsunami hazard, it falls short of offering a comprehensive
representation of the problems faced by PICTs. There is currently almost no grasp of local and regional volcanic- related tsunamigenic
sources and processes in the Pacific (e.g., eruptions, caldera collapse, flank collapse etc). For example, an eruption at Ritter Island,
PNG in 1888 produced a significant local volcanic tsunami and the 1452/1453AD eruption at Kuwae, Vanuatu produced a catastrophic
region-wide tsunami only recently recognised in the geological record. Many PICTs are still volcanically active and form part of the
PRF, while those not directly associated with it are generally either linked to hot spot volcanism, mid-ocean ridges, or past tectonic
activity. Perhaps most importantly, because most PICTs are volcanic in origin they rise up steeply 1000’s of metres from the seafloor
and as such are susceptible to tsunamigenic landslides.
On balance, it seems reasonable to suggest that simple subduction zone events may represent as little as 50% of the
potential tsunamigenic sources for some PICTs (e.g. Cook Islands, Kiribati, French Polynesia). While these challenges are not
insurmoutable, and indeed science advances by addressing such issues, for the time being all we can safely say is that we only have a
rudimentary knowledge of the risks posed by tsunamis to PICTs.
Even the modelling of moderately simplistic tsunami hazard scenarios is complex - all the way from source (e.g.,
earthquake, landslide, volcano) to inundation (e.g. water depth, speed, runup). Furthermore, modelling tsunami generation,
propagation and inundation faces the challenge of a lack of detailed offshore bathymetry and onshore topography including LIDAR
datasets which both act as impediments to producing realistic inundation and runup forecasts. Equally, current inundation models are
based on bare earth topography and fail to consider land surface roughness and vegetation, people and infrastructure. Finally, aspects
of later arriving and receding waves, and the interaction of debris or projectiles have not been included in many modelling studies.
EAP DRM KnowledgeNotes. Disaster Risk Management in East Asia and the Pacific. Working Paper, Series No. 25.
Available on the Internet: <http://wwwwds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2011/07/22/000356161_20110722030203/Rendered/PD
Early warning system
Tsunami warning systems do not exist in India because of the
relative rarity of tsunamis in the Indian Ocean. Tsunamis are rare in the
Indian Ocean, where seismic activity is less frequent than in the Pacific.
On the other hand, the greater frequency of tsunamis in the Pacific Ocean
has led to much greater investment in tsunami research in the countries
that have a coast on the Pacific. A tsunami warning system is in place
across the Pacific Ocean. An Indian Ocean Tsunami Warning system has
been proposed. However, it is estimated that its implementation might
take two to three years. In the meanwhile, it is suggested that the
vulnerable countries should form a part of the Pacific Ocean Tsunami
Warning system and have facilities for communication with the vulnerable
population. (Sonak et al. 2008)
Sonak, S., Pangam, P., Giriyan, A. Green reconstruction of the tsunami-affected areas in India using the
integrated coastal zone management concept. Journal of Environmental Management 89 (1), 2008, p.p. 14-23.