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DISASTER RISK ASSESSMENT Overview of Basic Principles and Methodology

George Pararas-Carayannis, Ph.D.

Retired Director, International Tsunami Information Center, UNESCO – Intergovernmental Oceanographic Commission

ABSTRACT Earthquakes, tsunamis, volcanic eruptions, hurricanes, storms, tornadoes, floods, landslides,

droughts and fires are among the major and most terrifying disasters which have taken hundreds of thousands of lives in recent years and have devastated the economies of many nations. Natural and man-made disasters differ from region to region - often affecting directly or indirectly populations of large geographical areas. Therefore, disaster risk assessment must be tailored to the specific threats of each geographical region. Mitigating the adverse impact of disasters and assistance for recovery, require proper planning, land utilization, civil defense preparedness, public education and the implementation of early warning systems.

Although each disaster for each geographical region often requires a different methodology in

developing a valid risk assessment plan, some basic principles apply to all. The present paper provides an overview of some of the basic principles and techniques that apply to the risk assessment of most disasters for rural as well as metropolitan areas. Furthermore it, illustrates the protective and preventive measures that must be taken to minimize disaster impact, alleviate potential problems, and help safeguard life and property.

INTRODUCTION The destructive impact of recent natural disasters on many regions of the world has brought into

focus the need for proper risk assessment, planning, preparedness and the implementation of early warning systems. The great earthquake and tsunami of December 26 2004 near Sumatra affected 13 countries bordering the Indian Ocean and was responsible for the deaths of more than 250,000 people. The great earthquake of 28 March 2005 in the same general area caused additional devastation. The hurricanes of 2005, and Katrina in particular, destroyed the city of New Orleans and other well-developed communities in the Gulf of Texas. The great earthquake of October 8, 2005 in Northern Pakistan and Kashmir was a reminder of the degree of devastation and human suffering disasters can cause.

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Regrettably, disasters such as these occurred in regions known to be vulnerable but where not proper risk assessment studies had been made and no adequate plans for preparedness or mitigation existed. If such studies had been properly made and plans were in place, the death toll and destruction would have been minimized.

Satellite Image of BandaSatellite Image of Banda Aceh Aceh taken on 2 Jan 2005 taken on 2 Jan 2005

Satellite image of Banda Aceh, in Sumatra, showing the extent of inundation and destruction from the tsunami of December 26, 2004

Unequivocally, disaster mitigation requires accurate and expeditious assessment of all potential

risks, the issuance of prompt warnings, and programs of preparedness that will assure warning effectiveness and public safety. The methodology for assessing the potential risks that threaten each region of the world requires adequate understanding of the physics of each type of disaster, a good and expeditious collection of historical data of past events, and an accurate interpretation of this data as to what future impact will be. Since each type of disaster results from different sources, the risk assessment methodology will vary accordingly.

Because of the extensive and specialized nature of disasters, it is outside the scope of the present

report to provide a detailed analysis of how all risks are determined for planning, zoning, construction or evacuation purposes. Each disaster requires separate treatment and analysis. This paper provides only a brief overview of general principles that apply to the risk assessment of all types of disasters.

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In the following sections, disasters are examined from a fundamental perspective, with emphasis on general techniques that must be used in assessing risks, with emphasis on mitigation, preparedness and public education.

UNDERSTANDING DISASTERS Understanding natural and man-made disasters can help mitigate their effects and help protect life

and property. Most of the natural disasters are comparatively rapid changes that affect the immediate human environment and safety. Earthquakes, tsunamis, hurricanes, volcanic explosions, floods or droughts have always been part of the natural cycle. In the last two decades such natural disasters have killed close to 3 million people worldwide, disrupted over 820 million lives, and caused more than $100 billion in property damage.

To the heavy toll of natural disasters, we must also add the impact of man-made hazards.

Accelerated changes in demographic and economic trends caused by population growth have disturbed the delicate balance between ecosystems on our planet, have seriously affected human health, and have increased the risk of human suffering, death and destruction (Pararas-Carayannis, 1986). The slower developing man-made disasters include pollution of the atmosphere and of the seas, destruction of our rain forests, alterations of sensitive ecosystems, or the destruction of the ozone layer. Climate changes we do not fully comprehend, like global warming or sea level rise, are slow disasters in the making that will have a long-term adverse effect on future generations.

A population explosion may be also a disaster of major proportions as it will impact on the earth’s

limited resources and environment. According to statistical reports published by the United Nations, the human population is now more than 6.5 million and is increasing at the rate of 210,000 per day about 76 million per year. There are projections that the world population may even reach 30 billion by the end of the millennium. Given these statistics of growth, it appears that the impact of natural and man-made disasters may be significantly greater in the future.

Natural Disasters We term the rapid changes that occur at inter phases of our planet and affect our safety and

property, as natural disasters. Weather-related natural disasters include hurricanes (typhoons) and associated surge flooding, tornadoes, heavy thunder storms, flash flooding floods, mud and rock slides, high winds, hail, severe winter weather, avalanches, extreme high temperatures, drought and wildfires. Major, weather-related geological disasters include earthquakes, volcanic eruptions, landslides and tsunamis and have been extensively reported in the scientific literature and Internet websites (Bolt 1977; Waltham, 1978; Frazier 1979; Whitlow, J., 1979; Walker, 1981; Maybury 1986; Steinbrugge, 1982; Pararas-Carayannis, 1968, 1976, 1977, 1979, 1980 1985, 1986, http://drgeorgepc.com), Most of the naturally occurring disasters are inevitable because they are beyond human control and cannot be prevented. Often, they are unpredictable, strike without warning and can result in great loss of life and destruction to property in a very short period of time.

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Recent natural disasters were responsible for great losses in life and extensive destruction to property. The official death toll from the October 8, 2005 earthquake in Northern Pakistan was more than 79,000. Another 1,300 people were killed in India.

Man-Made Disasters Man-made disasters include wars (conventional, biological, chemical or nuclear), toxic material

emissions and chemical spills (from trains, industrial plants or ships, riots or other civil disorders, nuclear plant melt down or other nuclear disaster, acts of terrorism, fires, pollution and man-made weather modification - if used as a weapon.

Hurricane Wilma over Florida in September 2005 (NOAA composite satellite image) Natural Disasters with Anthropogenic Contribution In the last two decades we have witnessed a remarkable increase in the frequency and severity of

weather related disasters such as hurricanes, tornadoes floods, wildfires, and droughts. Although these

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are considered to be natural disasters, anthropogenic input in the form of greenhouse gases emitted by industries into our planet’s atmosphere, has been blamed for climate change, global warming and sea level rise. It appears that a new era of super-disasters has made its ugly appearance. In 2005 there was a record of 26 storm systems in the Atlantic and most of them reached hurricane intensities. Nothing similar has occurred in the past. The contributing human factors can no longer be ignored. The seas are rising, the planet is getting hotter and there is an explosion in population and development in all regions of the world. . The damage to the ecosystems is unprecedented. The table below illustrates the range of disasters that impacted a small geographical region – Hong Kong.

Natural Disasters in Hong Kong Source: "EM-DAT: The OFDA/CRED International Disaster Database, Université Catholique de

Louvain, Brussels, Belgium" (By date and people killed)

WIND STORMS

(Typhoons and storm surges)

28-Aug-1937 11,000 8-Sep-1906 10,000 7-Oct-1947 2,000 28-Aug-1962 183 12-Aug-1923 100 15-Sep-1993 82 28-Aug-1962 72,000 4-Jun-1960 15,127 28-Jul-1979 12,090

17-Aug-1971 115 21-Aug-1968 3,004

FLOODS

Date Date

16-Jun-1972 138 11-Jun-1966 65 16-Jun-1972 14,607 11-Jun-1966 11,301 7-May-1972 7,565 6-May-1960 7,000 22-Jul-1994 4,017

LANDSLIDES

18-Jun-1972 100

WILD FIRE

Jan-1982 9,000

Global Warming: Rising populations and the cumulative and synergistic effects of environmental

degradation appear to have a significant effect in global warming and appear to have increased the frequency and intensity of weather-related disasters (Pararas-Carayannis, 2003 a, b). Intense weather related disasters have resulted in an increase of the human death toll. According to the World Disasters Report, weather related disasters in 1998 resulted in the deaths of thousands. Hurricane Mich killed 10,000 in Central America. Indonesia experienced the worst drought in 50 years. Floods in China affected 180 million people. Fires, droughts and floods - blamed on the El Nino weather phenomenon - claimed a total of 21,000 lives and caused more than $90 billion in damages.

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The on going climate change and accelerated global warming that our planet has been experiencing for the last few decades, represent the greatest long term disasters that threaten present and future generations (IPCC, 2001: Pararas-Carayannis, 2003 a, b). Unfortunately, these slow, global changes cannot be easily measured, quantified or mitigated. Although international treaties such as the Kyoto Protocol have been signed by most countries to reduce greenhouse gases, there has been no significant reduction in atmospheric concentrations. In fact, the world population increases have placed higher demands for the use of fossil fuels and the amounts of greenhouse gases in our atmosphere are increasing.

Other Anthropogenic Impact: Biological and chemical weapons, as well as weapons of mass

destruction, are also potential man-made disasters that threaten humanity. Weather modification, if used as a weapon rather than for mitigation purposes, may be a man-made contribution to what may appear as natural disasters.

Rare Disasters Finally, to the list of disasters that threaten humanity, whether man made or natural, rare disasters

include pandemic disease outbreaks (like bird flu), asteroid, mega volcanic eruptions and collapses, comet or giant meteor strikes, magnetic pole reversals and alien invasion. In fact, the looming health hazards of diseases and potential pandemics such as the Avian Flu may not be all that rare. About four pandemics occurred in the 20th Century. In 1918 to 1919 the so-called “Spanish Flu” or great influenza pandemic - which is believed to have originated in Asia - infected an estimated one billion people and claimed as many as 50 million lives. Presently, the Avian Flu – if not effectively contained - has the potential of becoming the world’s worse disaster. It is estimated that a pandemic of the avian flu could cause the death of 150 million people.

Need to Mitigate Disaster Impacts Human life on earth can only exist within a finite range of environmental conditions. Therefore,

assessing risks associated with long-term disastrous global changes is extremely significant but also very complex since it involves all aspects of human life and activities on our planet.

The assessment of long term disasters associated with climate change should be of great concern to

all nations and will require governments and international organizations to cooperate and continue to conduct synoptic data collection and studies to assess what the future global impact may be, as well as the means by which adverse trends can be stopped or reversed and the effects of weather related disasters be mitigated. Treaties and international agreements like the Kyoto Protocol are meaningless if there are no sincere efforts by the signatory parties to significantly reduce the anthropogenic input of greenhouse gases and other pollutants into the earth’s atmosphere, oceans and seas. Other than calling attention to the need for mitigating actions, the present overview cannot address or adequately describe a methodology for assessing the long term, disastrous changes on our planet.

It is inevitable that natural disasters will strike different regions of our planet over and over again.

Although numerous disasters can be expected, it is the occurrence of the bigger and more destructive

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ones that should be of concern to everyone, but particularly to government officials who are responsible for land utilization, construction of important infrastructure facilities, and public safety. Thus, disaster prediction and assessment of the risks should be of paramount importance to government officials of nations in disaster-prone areas, as well as to planners, engineers, scientists, architects and the general public.

The need for proper natural disaster risk assessment, particularly for areas known to be vulnerable,

cannot be overemphasized (Pararas-Carayannis, 2002) As we recently witnessed in Pakistan, Indonesia, US and elsewhere around the world, earthquakes, tsunamis, hurricanes and floods were particularly catastrophic because they occurred in densely populated regions where there was no adequate preparedness or proper assessment of risks.

Destruction in Northern Pakistan from the October 8, 2005 Earthquake (Photo Maj. David

Wakefield, Salvation Army) To plan for the mitigation of natural disasters there is a need for good understanding, not only of

the physical nature of the phenomena and their manifestations in each geographical locality, but also of that area's combined physical, social, economic and cultural factors. No matter how remote, the

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likelihood of all types of disaster occurrence should be considered. Disaster-related fatalities, injuries, and property destruction can be avoided or minimized by correct planning, construction, engineering, land utilization and effective public education and preparedness. Structures can be built that are disaster resistant. Many buildings and homes can be reinforced at a small cost to the individual, company, or state to withstand the effects of a disaster such as an earthquake, a hurricane or a tsunami. Construction codes can be upgraded.

Because of their destructiveness, natural and man-made disasters will continue to impact on the

human, social and economic sectors of our societies (Jones and Miha. 1982: Pararas-Carayannis, 1986). The need to assess the risks of disasters cannot be overstated. Sustainability of the planet and the safety of human communities require continuous vigilance and preparedness. Assessing the risks of potential disasters is a prerequisite in planning for their mitigation.

Countries bordering the Indian Ocean that were every impacted by the Destructive Tsunami of

December 26, 2004 Need for International Cooperation Proper coordination of national efforts is necessary to mitigate the impact of disasters.

Additionally, international coordination is often required to bring together scientific programs, engineering capabilities, and assistance with the establishment of early warning systems (Pararas-Carayannis, 1978, 1989). Such systems include an adequate array of monitoring instruments to collect necessary data and information for disaster evaluation, and to determine future risks. However, in order for disaster warnings to be of value, expeditious and effective international communications systems are necessary to insure proper dissemination throughout a large geographical area. Finally,

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when major disasters strike developing countries with limited resources, there is a requirement for international response to humanitarian and economic needs. Recent disasters in Southeast Asia brought attention to the need for international relief to the area stricken by disasters. The immense outpour of international support helped save lives and mitigate the threats of post disaster diseases.

Need for Advance Planning Regardless of the frequency of a disaster or the available warning time, an assessment of potential

risk and the planning for disaster mitigation must be made well in advance. An example of the lack of proper planning became evident when Hurricane Katrina struck New Orleans. The levees of low-lying New Orleans designed for surges of Category 3 hurricane were not adequate.

Google graphic of Hurricane Katrina’s path

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It is a well-known fact that destructive hurricanes occur with frequency in the Gulf of Texas. Historical destructive hurricanes have been well documented and numerically modeled (Pararas-Carayannis 1975, 2002). Since 1900, hurricane damages to coastal property have averaged more than $50 million per year. The hurricane surge is an oceanographic phenomenon and constitutes a greater hazard to lives and coastal property than the hurricane winds. Hurricane surges have been estimated to account for 75 to 90 percent of all deaths resulting from a hurricane. As hurricane Katrina proved, the surge inundation can be responsible for many deaths and extensive damage to coastal property.

Example of inadequate design. Hurricane Katrina surge flooded New Orleans when protective

hurricane levees failed or were overtopped. The levees were designed for a Category 3 hurricane. The storm that hit Galveston in 1900 resulted in 6,000 deaths and the almost complete destruction

of a large part of the city. Most of the deaths were caused by the surges. The hurricane of October 3. 1949, devastated the Yukatan Peninsula, Honduras and Guatemala before striking Texas. Surge heights were 11 feet at Velasco, 8 feet at Matagorda, 9 feet at Anahuac, and 11.4 feet at Harrisburg in the Houston Ship Channel. Hurricane Carla, which struck the Texas coast in 1961, killed 32 persons. The damage from Hurricane Carla was more than $400 million. Maximum surge height was 12.4 feet

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at Freeport Harbor. Hurricane Betsy in 1965 resulted in partial flooding of New Orleans. Betsy was responsible for 81

deaths and $372 million (1965 dollars). Hurricane Camille, which struck the Mississippi coast in 1969, killed 262 persons and caused damages of nearly $1 billion. Maximum surge height of Camille was 31.65 feet, 25.4 feet at Pass Christian and 20.4 feet at Biloxi, in Mississippi (Pararas-Carayannis, 1975). Hurricanes in the 70's, 80's and 90's have been even more destructive in terms of damage, but fortunately did not take as many lives as the hurricanes of the past – not until Katrina struck.

Even if there was no adequate risk assessment study for the city of New Orleans, basic history

alone could have been relied upon for planning purposes to mitigate the effects of Katrina. The flooding of New Orleans should not have been a surprise. Government officials and planners should have known about the city’s potential flooding vulnerability. The lack of planning in New Orleans for the mitigation of larger intensity hurricane surges and for appropriate post disaster recovery was inexcusable.

DISASTER RISK ASSESSMENT Overview of Some Basic Principles and Methodology

There is nothing that can be done to prevent the occurrence of natural disasters. Disasters will

continue to result in losses of lives, destruction to property and the disruption of the social and economic fabric of entire communities. The losses will continue to increase because of population growth in vulnerable areas, such as coastal regions, flood plains, and seismically active zones. But while disasters cannot be prevented, their impact on loss of life and property can be drastically reduced with proper risk assessment and planning.

A good starting point in assessing the vulnerability of a given region should be the identification of

potential disasters, the establishment of a historical database of past events, the delineation of the geographical distribution of potential maximum disaster impacts, and the preparation of a plan to mitigate adverse effects and protect life and property. The following discussion is limited only to some of the general concepts and basic principles that apply to the risk assessment of the most important of the natural disasters.

1. REGIONAL IDENTIFICATION OF DISASTER RISKS

Advances in science and technology provide the means to reduce significantly losses from disasters. But, in order to apply the needed techniques, it is important to first identify the potential disasters that may strike each geographical region.

Any given area of the world may be vulnerable to one or more natural disasters. Certain regions are

vulnerable to earthquakes and tsunamis. Other regions may be vulnerable to hurricanes, tornadoes or flooding, while still others may be areas that are threatened by volcanic eruptions, landslides or other

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localized hazards. Identifying the most important disasters and hazards for a given region is the first priority in developing a risk assessment study. For each type of potential disaster the risk assessment study will require different approach. However, there are some common elements in assessing the impact of all disasters.

1a. Development of Historical Databases After identifying the disasters that may be of threat to a region, a good starting point for the

disaster risk assessment study is the collection of data of all the historical events that caused destruction in the past. The data collection becomes easier if the region is known to have sustained disaster damage in the past and if good records have been kept.

A historical disaster database can be developed for a certain region by researching miscellaneous

archives of newspapers and public records. If such historical data is unavailable, the data may be developed from indirect sources. For example, in compiling a historical database on tsunamis in the Pacific Ocean, the cemetery records of coastal cities and villages in Japan were examined to determine what events might have caused deaths during a certain time period.

Other indirect ways in developing a historical data base for past events may be the examination of

old correspondence of government officials or of accounts of early missionaries and settlers. For example, a search of the records of Franciscan Missions discovered a wealth of historical earthquake and tsunami data for California. Similarly, searches of the Archives of Seville and of correspondence of Spanish Conquistadors with the Kings of Spain, helped develop a historical database on earthquakes and tsunamis in South America beginning as early as 1542.

In the absence of historical data, past disaster events can be determined by studying the geologic

stratigraphy of a region and using radiocarbon, other isotope dating techniques or dendrochronolgy to establish their occurrences and their severity. For example, by studying past seismic activity, geologists can often speculate on what controls the dynamics of earthquakes and make predictions. Often one earthquake may nucleate an offset along the trace of a fault and such offsets and measurements of strain build-up can be used to forecast, not necessarily the exact time of the next earthquake event further down the fault rupture, but at least its magnitude and location.

The development of a comprehensive and systematic compilation of historical data on disasters is

an indispensable tool for disaster risk analysis and can also serve in the operational analysis and real-time evaluation of potential disaster threats by early warning systems. Finally, a historical disaster database can be widely used for coastal zone management, engineering design criteria, educational purposes and disaster preparedness. Internet communications and software can also help make interactive retrieval of historical data on disasters feasible for global sharing, and for international programs of disaster mitigation.

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2. STATISTICAL METHODS IN ESTABLISHING DISASTER RECURRENCE AND SEVERITY

Once the disasters have been identified and the historical data collection has been completed for a

region of interest, the next step in the risk assessment study is to treat the data statistically to establish recurrence patterns for each type of disaster. In order to develop a plan for the mitigation of a disaster’s impact, the risk assessment study must first determine - or at least estimate - where and when future events may occur again. If possible, the statistical analysis must further differentiate between expected yearly or seasonal occurrences of frequent hazards, such as those that are weather related, and of extreme events of longer cycles, like large destructive earthquakes, tsunamis or volcanic eruptions. Statistical Methods in the Atmospheric Sciences have been very successful (Wilks, 1995).

Statistical techniques are often used to show the specific probability of occurrence of selected

disaster parameters in a specified time interval. However, such statistical analysis requires good historical data on past events – as described in the previous section. If there is no sufficient historical data, forecasts of disasters based on statistical methods are not very accurate.

2a. Disaster Frequency The most important parameter in risk assessment is the determination of the disaster’s recurrence

frequency. Assuming that the historic record is long enough and there have been many years of direct observations, it is possible to establish approximately when a disaster may be expected again. However, if the historic record is limited, statistical methods are of no use.

The problem is that large catastrophic disasters may take place so infrequently in any one location

that there may be no locally available data on which to predict risk and produce a zonation of the hazard. The lack of historical data should not be misinterpreted to mean that there is no danger.

Therefore, the prediction of infrequent disasters: such as earthquakes, tsunamis or floods - are often

given in statistical terms but with a great deal of ambiguity. For example, when a statistical prediction is made that "there is a 90 percent chance that an earthquake will occur in the next 50 years," in a certain area known for its seismicity, this does not mean that the predicted earthquake cannot happen tomorrow or that it may not be delayed by 50 years. Similarly, floods are estimated in terms of statistical probability of being 50, 100 or 200-year events – which nature may very well prove wrong.

Obviously, statistical predictions of infrequent disasters may not be within a reasonable time frame

that can be of usefulness to planners, policy makers, and those in government who deal with public safety. However, the statistical analysis of seasonal disasters such as hurricanes or storms can be forecasted more easily and can be fairly accurate. In conclusion, if a good historical database exists, it is possible to develop the statistical probability of a disaster’s recurrence.

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2b. Statistics of Extreme Events The recurrence intervals of exceptionally large phenomena bear consistent relationships to their

magnitude expressed in either arithmetic or logarithmic terms. Thus, 50 years of data can be used to extrapolate and determine the once-in-a-thousand-year event. This approach is rather vague as the confidence limits are usually so large that the resulting estimates of recurrences are principally meaningless. On this basis it is very difficult to accept the statistics of extreme events as the basis for planning, land use or construction. In such cases one may have to resort to disaster modeling studies. 3. DISASTER MODELING STUDIES

If there is insufficient historical data, the only way to assess potential risks of a region to rare

disasters is through the application of physical or numerical models. Such an approach must postulate the occurrence and parameters of a disaster and thus determine indirectly the impact it would have - if and when it strikes. For such modeling studies, potential worse case scenarios are used to determine the severity of impact. Additional modeling simulation may be also made with smaller sources to determine the severity of less extreme but more frequent disaster events.

The modeling methodology will be different for each type of disaster. It must include both local

and distant sources and the transformations and other associated hazards during its development. The results must include terminal effects and expected static and dynamic forces at selected impact regions. All disasters can be modeled.

3a. Physical Scale Modeling of Disasters Making scale models of the region of concern and introducing scale models of buildings and other

aspects of land use may simulate a disaster and study its impact. The simulated disaster effects may be produced mechanically and the impact can be photographed, measured, and recorded. For example, hydraulic models have been built by the U.S. Corps of Engineers to assist in predicting the effects of potential floods, or failure of dams. Geologists and engineers use sophisticated shake tables to simulate earthquake motions and determine effects on structures. Physical models are expensive to construct and difficult to scale down in size both geometrically and kinematically. However, physical

models have been very useful in assessing the risks and effects of different types of disasters. 3b. Mathematical Modeling of Disasters Computer models using correct input parameters permit relatively accurate predictions of potential

disaster effects and can be invaluable in risk assessment studies. Regardless of the disaster, the construction of computer models must involve four common elements. The first of these elements is an initial analysis of the physical characteristics of the disaster. This permits the subsequent development of the mathematical model, which must be capable of forecasting the severity of impact for different disasters of varying magnitude. Such an approach leads to the development of the spatial

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pattern of impact intensity, which then can be used for the microzonation of the hazard. Each disaster will require the solving of different sets of mathematical equations, which will show finite differences of progression as the disaster develops. The following overview provides a few examples on the use of mathematical models for natural disaster risk assessment.

A hydraulic model simulating tsunami inundation and effect on buildings 3b1. Tsunami Modeling: Tsunamis can be studied with both physical and numerical models.

Most numerical models of tsunami impact deal primarily with the extent and' height of tsunami inundation leaving most of the other engineering interpretations to planners and engineers. However, from such models, the extent of damage can be estimated and evacuation limits can be established to minimize deaths and injuries along the shore. This information is normally presented in a map form with tabulations so that both the spatial distribution of gross impact and associated risk can be established. This is the final result and use of data provided by numerical models. The following is a brief description of how a reliable mathematical tsunami model must be developed for risk assessment purposes.

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Tsunamis can be generated by numerous types of other disasters such as earthquakes, volcanic eruptions, landslides, rock falls, nuclear explosions, methane hydrate collapses below the ocean bottom, and even from extremely rare collisions of asteroids or comets with the earth. Often, various source models and scenarios of generation/impact must be examined. For each type of source event, the mathematical modeling of tsunami generation will be different and will require the use of complex mathematical relationships to describe the coupling impact effect with a body of water. The accuracy of numerical models in estimating near and far field tsunami effects depends on initial input parameters derived from realistic assumptions of generative mechanism. Because of the complexity of source events, the mathematical tsunami model must make valid assumptions on the correlation of the initial water displacements to tsunami wave length and period in the source region, regardless of the generative mechanism - whether an earthquake, a landslide, or an impact event such as a rock fall or an asteroid (Pararas-Carayannis, 2002).

Once the tsunami source mechanism is realistically established, and then the appropriate

mathematical equations must be used to describe the tsunami wave propagation and the terminal effects at a local or distant shore. In determining tsunami propagation and runup heights, finite difference models are used extensively with varying success. Assumptions are usually made about spatial conditions existing in the neighborhood of a moving boundary resulting in the development of a flooding scheme, which allows the governing differential equations to be applied uniformly across the computational grids.

Recently, using supercomputers, researchers at the U. S. Los Alamos National Laboratory and

Science Applications International Corporation, developed a compressible Eulerian hydrodynamic code which permits three-dimensional modeling of tsunami generation, propagation and inundation from a variety of tsunami source mechanisms - including asteroid impact (Mader, 2005, Weaver et al, 2002). These new tsunami models provide for very realistic graphic representations - in the form of three-dimensional moving simulations - showing the result of finite differences at every time step.

3b2. Hurricane (Typhoon) and Storm Surge Modeling: Although usually erratic and

unpredictable, hurricanes generally follow a westerly to northwesterly path toward the gulf or Atlantic coasts. Typhoons follow a similar pattern in the western Pacific. Numerical modeling of hurricanes is fairly simple. Their paths, wind velocities and landfalls can be estimated with remote sensing methods, airplane penetrations and satellite photographs. Hurricane winds spiral inward toward a center or eye of low pressure at speeds, which may reach more than 150 miles per hour (130 knots). The hurricane wind field is now easier to determine because of the new technology. Numerical models are used to develop the three dimensional wind field of a hurricane, the radius and ever changing direction of maximum winds and the landfall.

3b3. Hurricane Surge Modeling: Increased residential development and large coastal

installations, such as power plants and super port terminals, emphasized the need for more accurate estimates of the abnormal water level fluctuations associated with a hurricane. These water level fluctuations are known as storm surges and are caused by the atmospheric pressure field and wind stress on the water surface, accompanying the moving storm systems. Specific factors which can combine to produce extreme water fluctuations at a coast during the passage of a hurricane include:

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storm intensity, size, path, duration over water, atmospheric pressure variation, speed of translation, winds and rainfall, bathymetry of the offshore region, astronomical tides, initial water level rise, surface waves and associated wave setup and run up due to wind frictional effects.

The capability to predict hurricane surges is based primarily on the use of analytic and

mathematical models, which estimate the interactions between winds and ocean. The prediction of sea surges resulting from the combined meteorological, oceanic and astronomic effects coincident with the arrival of a hurricane at the coast is more difficult problem to solve. The reason is that a hurricane is a three-dimensional, weather system with ever changing dynamic conditions of wind speeds, directions and atmospheric pressures. It will not be attempted here to explain exactly how the problem is solved. Only some of the basic concepts and components - which cumulatively contribute to hurricane surge - will be explained.

Many sophisticated mathematical models have been developed in recent years to provide accurate three-dimensional estimates of energy flux and flooding that can be caused by a passing hurricane. All models, regardless of sophistication of methodology, must use the Bathystrophic Storm Tide Theory to estimate the rise of water on the open coast - taking into account the combined effects of direct onshore and along shore wind-stress components on the surface of the water, the effect of the earth’s rotation – known as the bathystrophic effect - and the different pressure and frictional effects (Pararas-Carayannis, 1975, 1992, 2004).

To model a hurricane and calculate its maximum surge heights, the following meteorological parameters must be first determined. These are the hurricane's central pressure index, its peripheral pressure, the radius to maximum winds, the maximum gradient wind speed, the maximum wind speed, and the speed of hurricane translation (overall speed of the system). The models of oceanic/atmospheric interactions also take into account numerous other factors, such as astronomical tide, existing ambient wave conditions, surface and bottom friction and coastal topography. Only then one can proceed with the solution of the complex hydrodynamic equations of motion and continuity that will allow determination of the time history of expected changes in sea level associated with the hurricane, at any given point.

Mathematical models using the Bathystrophic Storm Tide Theory can be quasi-one-dimensional,

two dimensional, or three-dimensional numerical schemes. The simplest, which is superficially described here, is a quasi-one-dimensional model which is a steady-state integration of the wind stresses of the hurricane winds on the surface of the water from the edge of the Continental Shelf to the shore, taking into consideration some of the effects of bottom friction and the along shore flow caused by the earth's rotation. This bathystrophic contribution is an important parameter of the hurricane’s surge and must be further explained.

In the northern hemisphere hurricane winds approaching the coast have a counterclockwise

motion. Because of the Coriolis effect due to the earth’s rotation, the flow of water induced by the cyclonic winds will deflect to the right, causing a rise in the water level. The bathystrophic storm tide, therefore, is important in producing maximum surge even when the winds blow parallel to the coast.

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Components contributing to height elevation of hurricane surge (Source: Pararas-Carayannis,

1975)

The nonlinear storm surge can be computed at selected points along the traverse by integrating numerically the one-dimensional hydrodynamic equations of motion and continuity. The hurricane surge estimated by this simple, quasi-one-dimensional model is a composite of water elevation obtained from components of the astronomical tide, the atmospheric pressure, the initial rise, the rises due to wind and bottom friction stresses, and wave setup. The model uses the onshore and along shore wind-stress components of a moving wind field over the Continental Shelf, and a frictional

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component of bottom stress. Such methodology was used to determine the time history of wind and surge flooding of Hurricane Iniki in September of 1992 along the southern coast of the Island of Kauai (Pararas-Carayannis, 1992).

The above diagram portrays graphically the various components, which contribute to the

cumulative total of hurricane surge on an open open-ocean coast (Pararas-Carayannis 1975). However, coastal morphology may also affect the extent of rise of water. This probably occurred with hurricane Katrina when the New Orleans levees were overtopped and failed from higher surge approaching from the direction of Lake Pontchartain from the north of the city as shown in the Quick Bird satellite Infrared image below.

The numerical models for hurricane surge prediction are fairly accurate and can be verified with

historical hurricane surge data. Recently developed numerical models using a three dimensional approach, faster and more efficient computers, and more accurate weather data from satellites, have greater potential for more accurate predictions. However, the fundamental principles in the numerical prediction of hurricane surge described here remain essentially the same.

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3b4. Earthquake Disaster Modeling: The physical processes of earthquakes are not fully

understood and are difficult to scale down and simulate with mechanical models. Therefore, numerical models have become an important aspect of the scientific research effort to understand the physics and recurrence frequencies of earthquakes – particularly the very large ones (Chinnery and North, 1975; Ward, 1996). There are many ways that earthquakes can be studied by numerical means for research purposes. However, an extensive description is outside the scope of this report. It will suffice to say that there are three general classes of synthetic earthquake models which use finite-element or finite-difference codes to determine temporal changes prior to or during an earthquake.

The first of these classes involves microscopic models (Pisarenko and Mora, 1994; Mora et al.,

2000). Such models deal with the micromechanics of rock material behavior at the smallest scale prior to or during an earthquake. The second type of modeling is at a higher scale and simulates elastodynamic processes, and more specifically the kinematics of earthquake rupture propagation (Ben-Zion and Rice. 1993, 1997; Oglesby and Archuleta, 1997), which then can be used to model the resulting seismic waves and their effects. The third type is the quasi-static model of much larger scale that helps determine the space-time patterns of earthquakes (Rundle, 1988a,b; Pisarenko and Mora, 1994; Eneva and Ben-Zion. 1997; Tiampo et al., 2000). Such models can be checked with historical earthquakes or can be used with synthetic events.

A different type of earthquake modeling is used for application in risk assessment studies and for mitigation and preparedness planning. Such models simulate an earthquake’s motions and estimate potential structural damage, as well as the human and economic impact of future disasters. For example, structural engineers and geologists use such models to study the different frequencies at which the various classes of earth materials at a certain region will amplify ground motions during an earthquake. Sophisticated computer modeling techniques are employed to simulate an earthquake’s shear waves and thus help understand the effects of shear wave amplification on buildings and other infrastructure for better design of structural elements.

A big problem of concern to scientists, engineers and planners is ground "liquefaction," a process

that occurs often during an earthquake and which can shift, sink or damage buildings and cause collateral damage to other facilities. In fact, such collateral damage from such liquefaction may be more destructive than the earthquake itself and may include flooding, fires and loss of vital services to a community. Therefore, proper modeling of liquefaction potential may help mitigate an earthquake’s collateral damages Finally such models can generate probabilistic ground-shaking maps, which can be used by the insurance industry.

3b5. Modeling Volcanic Eruptions: Although violent volcanic eruptions are not frequent, officials in communities located near active volcanoes must include this hazard in risk assessment studies. In addition to the data obtained from historical events, worse case scenarios should be included and numerical modeling should be used to evaluate potential impact of volcanic eruptions, atmospheric shock waves, pyroclastic flows, nuees ardentes, lahars, and other hazards such as flank and caldera collapses, as well as tsunamis generated by such mechanisms.

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Several numerical models have been developed on volcanic eruptive mechanisms, but few of these models can be used for planning purposes and hazard mitigation. For example, a two dimensional finite differences model was used to correlate seismic recordings with activity of an active volcanic vent of the Soufriere Hills volcano on Montserrat Island, in the Caribbean. The results of the model described the periodic behavior of events and increases in the eruption frequency in a volcanic dyke. However, this type of modeling is of a small scale. Although significant in understanding the physics of eruptions, it is of limited value for risk assessment analysis.

The 1991 eruption of Mt Pinatubo in the Philippines.

Of greater usefulness for risk assessment purposes are models that can be used to forecast the

impact of volcanic eruptions and associated hazards on a greater geographical scale. For example, NOAA’s Air Resources Laboratory (ARL) developed a 3-dimensional Volcanic Ash Forecast Transport and Dispersion model. This is a real time, short-term, forecast model that describes the ash transport and dispersion in the atmosphere following a major volcanic eruption. The model integrates volcanic and meteorological data to determine extent of ash transport and dispersion (Heffter and Stunder, 1993). Required inputs are the location of the volcano (latitude and longitude), the summit height, the date and time of the eruption, the duration of the eruption, the ash column height, and the gridded meteorological data at the time of the eruption. Several eruptions of volcanoes in Alaska,

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Indonesia, Kamchatka, Mexico and Montserrat Island were monitored to develop and verify the model (Heffter, 1996). The forecasts generated by this type of model can be also verified with remote sensing techniques and satellite imagery.

3b6. Tornado Modeling and Forecasting: Tornadoes are seasonal disasters that strike suddenly,

frequently but usually in areas known to have sustained damage in the past. However, over long periods of time there is significant variability in their climatology (McCormick, 2000). Tornado forecasts and warnings are usually issued on a short-term basis since they involve rapidly developing weather subsystems.

Recurrence period for F2 or greater tornadoes in thousands of years based on Monte Carlo simulations

(After Meyer et al. 2005).

The use of tornado modeling has become essential in risk analysis and hazard mitigation (Schaefer et al, 1986). Knowing where approximately the tornado may strike and its probable intensity, individuals and businesses can be better prepared for significant events - tornados with a designation of F2 or greater on the internationally adopted Fujita intensity scale (Brooks and Doswell, 2001). Officials in areas with large populations can develop better plans for preparedness. With advance forecasts provided by tornado models, damages, injuries and deaths can be reduced significantly.

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The advent of new computer technology and synoptic observations - made possible by remote sensing and satellite imagery - have greatly facilitated the use of numerical tornado models and the understanding of the physics of the hazard and its potential long and short term risks (Brooks and Kay, 2001). Also, a statistically significant historical database of about 10,000 tornadoes has been compiled for a 75-year period from 1921 to 1995 (Grazulis, 1993). This database has been augmented and has helped establish good climatology for this hazard (Doswell and Burgess, 1988; Kelly et al., 1978).

The database includes, path lengths and widths and Fujita intensity scale designations ranging from

F0 to F5. Violent tornadoes are those classified F2 and greater. Through the use of numerical models, tornado occurrence, location, path length, path width, and Fujita scale of intensity can be determined (Concannon et al., 2000). In fact, using the historical database, models were developed to determine specific patterns of recurrence and spatial variabilities of intensity for different regions in the United States (Schaefer et al., 1986). Similar models - extrapolated statistically from the known historical data – have helped to establish long-term patterns and to analyze for variability between different time periods and thus establish overall risks and future impacts. The model used for this purpose has been the Monte Carlo Model, which essentially provides a statistical approach to the long-term, risk analysis of the tornado hazard (Meyer et al. 2005)(See figure above on tornado recurrence periods).

3b7. Accuracy of Numerical Modeling: Numerical modeling has made the job of predicting the

effects of numerous disasters much easier and has become an indispensable tool in risk assessment, land use management and construction of critical structures. It is particularly useful when verification and calibration can be accomplished with historical data or through the use of analytical solutions with experimental results.

However, in addition to emphasizing the value of numerical modeling in risk analysis, a word of

caution must also be given. The accuracy of numerical models in estimating disaster impact will depend on initial input parameters derived from realistic assumptions of generative mechanisms (Pararas-Carayannis, 2004). Furthermore, in modeling, particular attention should be given in avoiding the introduction of errors and artifacts, which may affect significantly the results (Kowalik, 2002).

4. DISASTER RISK MAPPING

Having completed the preliminary stages, the analysis of the disaster risk must now be translated

and reduced from technical and scientific terms to simple forms that can be adopted and used effectively. The analysis must be simplified further into forms that can be understood easily by the general public. Thus, the final product of historical, statistical or modeling studies must indicate the spatial variations of the hazard risk in the form of maps. Maps can be prepared for all natural hazards that may impact a geographical region.

The production of maps depicting variations in the degrees of disaster risk is an invaluable tool for

the planning process and for proper land management. In this way, high-risk areas can be avoided or used for low intensity development and safe areas can be designated for public shelters and

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evacuation. Similarly, the total risk at any point can be easily established, as well as the probability of occurrence for insurance purposes.

4a. Variation and Acceptability of Risk Determining the variation of risk is a key element in planning and preparing for future disasters.

For example, based on historical earthquake or hurricane activity, appropriate maps can be prepared depicting the risks for each region. For some regions, such maps already have been compiled. For example, four zones usually represent seismic risk in accordance to expectancy of earthquake damage. According to this type of zoning, areas are designated that have no reasonable expectancy of earthquake damage; areas where minor damage can be expected; areas where moderate damage can be expected; and finally areas where destructive earthquake effects can be expected. Hurricane maps may show their customary tracks, seasonal and chronological occurrences, and areas of past impact and heights of surge inundation.

Example of Multi-Hazard Zonation at Eureka, California, showing areas vulnerable to tsunami

inundation, ground liquefaction, landslides and higher seismic intensities.

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4b. Microzonation of disaster risks Although mapping of hazards is useful for overall risk assessment, the selective nature of a

disaster’s destruction along a given region often requires mapping which takes into consideration specific local conditions. Public officials and planners can develop better disaster response and recovery plans if they know the possible physical and economic damage and the various disaster scenarios and collateral impacts which may affect structures and businesses. Also, structural engineers need more accurate analysis and more detailed information in the form of microzonation maps of the hazard so that they can design structures that will withstand the impacts and additional structural loads. Such detailed maps are essential to planning and disaster reduction.

August 4, 1982, Landslide at Tsing Yi Road, Hong Kong. Cause of failure was the slide of the

upper section of a decomposed granitic layer above another critical failure surface. This is an example of how microzonation could have helped evaluate the potential risk.

For example, in assessing the specific earthquake risk of a given region, an earthquake source must be postulated of a given magnitude and location. Then all geological materials in the area with similar

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physical properties are grouped together. Subsequently, the effects of the postulated earthquake for each geologic unit are predicted by type of hazard for failure, specific type of ground shaking, surface rupture, flooding, land sliding, and liquefaction potential. Finally, zones on a microzonation map combine all the geologic effects as described previously. With such maps engineering geologists can estimate potential amplification of ground motions during an earthquake and engineers can design proper new structures or retrofit existing ones.

4c. Map Scale Considerations Maps are used by state and local officials to estimate potential disaster losses and to prepare

emergency response plans. An adequate scale for compiling maps for this purpose is usually 1:24,000 (1 inch equals 2,000 feet); Microzonation of earthquakes or other hazards may require a more detailed scale.

In producing maps of the different hazards, attention should be paid to scale requirements so that

the significance of the hazard can be easily identified and correlated to prominent landmarks. Such maps should be sufficient for precise planning of land use and should include vertical and horizontal parameters of scaling that are sufficiently large. For example, the initial tsunami inundation maps that were produced for Hawaii had scales of 1:63,360, and 1:24,000. All that can be really suggested is that the selected scale be large enough to make full use of the available data and thus permit individual sites and structures to be identified, if possible. However, the scale should not be so large that it gives an invalid impression of precision in areas where the information does not warrantee such an assertion.

5. LAND USE ANALYSIS

A global population expansion and increased development at an ever-increasing rate – particularly

in critical disaster-prone areas of the world - are threatening entire communities. Improper land use and development have significantly elevated the risks and potential losses of human life and resources from future disasters. In view of such threats, good risk assessment studies are needed to provide the geographical distribution of disasters and recommend steps that must be taken by communities to mitigate disaster impact through appropriate land utilization.

Although underutilized, controlled land use is an indispensable tool for mitigating the adverse

impact of disasters. Therefore, it is imperative that a disaster risk assessment study includes or is followed up by a proper analysis of how the land should be utilized to mitigate disaster impact on a community.

A land use analysis could be included in the risk assessment evaluation or developed subsequently.

Such analysis must examine carefully the findings of the disaster risk assessment and designate what use of land should be made, where the safety zones for urban development should be, where important community infrastructure could be located, and what engineering guidelines and building codes must be adopted. This is not an easy task. The decisions on land use cannot be left to officials

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and planners alone. The tremendous variety of possible direct and collateral damages from disasters make it extremely difficult for community planners to predict what the expected damages may be, what emergency responses may be needed, what zoning and building code changes may be necessary or how land zoning could be used effectively to mitigate disaster impacts. Therefore, all decisions regarding the use of land should be made collectively, with input and consultations with scientists and specialists who have intimate understanding of the physics and ramifications of disaster phenomena.

A disaster risk assessment would have identified the potential for the disastrous mudslide of February 17, 2006 that buried the village of Guinsahugon on Southern Leyte Island, in the

Philippines. In November 1991, floods and landslides triggered by a tropical storm killed about 6,000 on that island. Another 133 people died in floods and mudslides in December 2003. Proper land use

would have indicated the need to relocate Guinsahugon village outside the path of the potential mudslide. The residents ignored warnings to evacuate.

5a. Loss Estimation Methodology A good starting point in developing proper land use policies is to determine what losses can be

expected if a disaster strikes and therefore what changes should be made to the existing use of land - or to future use of land - to reduce these losses. Such methodology of loss estimation should be an integral part of the disaster risk assessment and of the official planning process. This approach can be expected to generate a list of social and economic losses that could result from different disasters and help determine what acceptability of risk can be tolerated – if any. For example, based on the disaster risk assessment study, this methodology could help determine what important structures - such as

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bridges, highways, or other infrastructure facilities - may be damaged or destroyed when the disaster occurs and what the cost of replacement or repairs may be. Such information would be of great importance and value to local governments but also to the financial and insurance institutions, as well as the public.

Of course such methodology of loss estimation is not an exact science and it is not always possible

to anticipate all of the collateral damages of a disaster. However, an educated estimate can be obtained. For example, based on probabilistic earthquake intensities as outlined in a microzonation map resulting from a risk assessment study, estimates on building damages may be deduced and the indirect economic losses be estimated. The same could be done with other disasters such as hurricanes, or floods. However, applying this methodology is not an easy task. It requires the development of a complete database of all the demographic and economic data of a community and the development of realistic methods for evaluating potential damages and estimating the various losses.

5b. Public Safety Of paramount importance in land use analysis should be public safety and the means by which it

can be assured through proper planning and land utilization. Development policies and decisions on public safety must be based on a comprehensive disaster risk assessment of all environmental hazard impacts that may be unique to a region. Government agencies have the responsibility to formulate land-use regulations that will result in greater public safety. Proper land utilization policies must prohibit urban development in zones that the disaster assessment study identified as potentially vulnerable and may put parts of the population at risk. Furthermore, the government agencies must designate evacuation procedures, post signs and provide proper instructions to the public. Property and business owners could also be educated about steps they can take voluntarily to protect their investments, if these are located in risk areas.

5c. Transportation Systems Construction or Modification Based on a proper disaster risk assessment study, government planners must construct appropriate

transportation systems or modify existing ones, to facilitate the rapid evacuation of people out of vulnerable zones. This should be part of land use analysis and contingency planning. The lack of such planning became evident when the surge of hurricane Katrina broke the levies and flooded the city of New Orleans. There was no contingency plan or operating transportation systems to evacuate people out of city or even out of flooded areas.

5d. Sitting of Infrastructure Facilities As part of a land use analysis and planning, government policies must encourage low intensity uses

for sites that are most susceptible to a given hazard, or other similar socially and economically non-disruptive land utilization. Such considerations of proper land use are particularly significant in developing infrastructure and industrial facilities - since their destruction or damage could compound the effects of a disaster by other indirect means such as leakage or spilling of flammable or hazardous

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materials. Therefore, decisions on development must be made carefully to protect a community’s infrastructure. For example, local governments could take steps to prevent certain kinds of development in areas likely to be flooded by tsunamis or hurricane surges, or building near earthquake fault zones. Critical facilities include schools, playgrounds, nursing homes, police and fire departments, hospitals and tourist facilities - such as beachfront hotels where people congregate - or places where the elderly, or handicapped persons may be at risk. The same information can be used to assess the risks to important infrastructure facilities – such as nuclear power plants - and the need to locate them in less vulnerable areas.

The Hurricane Surge Protective Defense Works in New Orleans were insufficiently designed to prevent the flooding. Levees were breached or failed considerable distance inland from the shore of

Lake Pontchartrain,

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5e. Protective Defense Works: Based on the disaster risk assessment study and the land use analysis, government agencies should

undertake the construction of protective defensive works on areas designated to be vulnerable. For example, sea walls, sea dikes, breakwaters, river gates and levees could be built to protect coastal areas where tsunami and other marine hazard threats are great. Such major efforts in building protective defense structures have been carried out in Japan, particularly along the Sanriku coast. These activities were motivated in large part by knowledge of potential inundation zones, and damage from past tsunamis, as documented by risk assessment studies. Unfortunately, as hurricane Katrina demonstrated, some of the protective defense structures in New Orleans - the levees – were not adequately designed and were breached or failed.

Protective walls and sea gates at Ofunato, Japan, were built to protect the coastal area and the port from large destructive tsunamis.

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Sea Gate protecting the port of Rotterdam in Holland from North Sea Storm Surges. 6. ENSURING THE SAFETY AND RELIABILITY OF IMPORTANT INFRASTRUCTURE FACILITIES

As part of a land use analysis and planning, the need for proper sitting of important infrastructure facilities was briefly discussed in terms of safety and non-disruption of operations. The following section addresses the engineering considerations that will ensure the safety and reliability of important facilities – if and when a disaster strikes.

Designing and constructing important infrastructure facilities must always take into consideration

all potential forces associated with a natural disaster. To ensure the safety and reliability of such facilities, all direct and indirect environmental impacts must be evaluated. The risk assessment study must provide detailed information and guidelines so that planners can use safe sites for construction but also for engineers to design proper structures that will sustain no damage and will continue uninterrupted operations in the post disaster period.

6a. Engineering Design Adequacy Earthquakes, tsunamis, hurricanes, storm waves, floods, tornadoes, landslides and a variety of

other natural disasters interact differently with structures. Therefore, building codes - but particularly the engineering design of critical infrastructure facilities - must be based on careful analysis of all

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static and dynamic loads and forces that could result from a variety of potential hazards. Each type of disaster will have different types of impacts and loads upon structures, their foundations and their auxiliary support systems.

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Critical highway section in California destroyed by the 1994 Northridge earthquake

The engineering design of structures in vulnerable regions must be extremely conservative and be tailored for specified impacts and loads. It cannot be based simply on past maximum events - because there is always the possibility that the impact of a new disaster may exceed those of past historical events. For example, the building codes that were put into effect following the 1933 Long Beach earthquake in California were found to be inadequate when an earthquake struck the San Fernando Valley in 1971, thus forcing the adaptation of new codes. When the Northridge earthquake struck the same general area again in 1994, the horizontal and vertical accelerations associated with this earthquake exceeded all the design criteria that had been adopted as adequate up to that time. Therefore, in evaluating the earthquake hazard effects for the selection of a building site for a critical structure, not only the seismic source regions should be identified in terms of geographical

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distribution and frequency of occurrences be estimated, but the expected peak ground accelerations (horizontal and vertical) must be evaluated also, to make sure that the structure will withstand these forces.

Horizontal ground accelerations of the January 17, 1994 Northridge earthquake. Note maximum acceleration of 2.0g.

The design adequacy of a critical structure to hurricane (typhoon) wind forces and associated flooding due to storm surges requires a different type of analysis. Essential to the design of an important structure to these types of hazards is the prediction of wind velocities and the elevations storm surges will reach due to the combined meteorological, oceanic and astronomic effects. As indicated earlier in discussing hurricanes and hurricane surge modeling, this may be a little more difficult to determine because a hurricane (typhoon) is a three-dimensional, dynamic weather system with continually changing direction and wind speeds. Because of the ever-changing dynamic conditions, it is also a little more difficult to calculate the height of the hurricane surge and the total water flux energy at different coastal locations. However, the construction of important critical structures, such as nuclear power plants, requires the adaptation of very conservative design criteria. For example, to ensure the safety of nuclear power plants in areas known to be vulnerable to hurricanes, the U.S. Nuclear Regulatory Agency requires that a Maximum Probable Hurricane be

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used to determine the surge that can be expected at the site. This is a design hurricane that is very conservative with winds exceeding category 5, thus ensuring that the nuclear power plant and its cooling systems will not fail even if such a super hurricane strikes the plant directly.

Nuclear power plants need to be located near a water supply. The plant’s cooling water pumps must be at a high enough elevation to prevent flooding and failure from a tsunami or hurricane surge.

The need for proper planning and sitting of critical structures for extreme natural hazards became

evident when the destructive tsunami of December 26, 2004 struck the Atomic Energy Township of Kalpakkam, on the east coast of India. The tsunami waves killed 37 people, destroyed 670 residences but also flooded the cooling system of the nuclear power generating facilities. It is not known what other impact the tsunami had on the Township of Kalpakkam, The Critical Nuclear Complex at this location includes other facilities such as: a) the Kalpakkam Atomic Reprocessing Plant (KARP) (which reprocess spent fuel from the pressurized heavy water reactors - including those known as MAPS-1 and 2 to produce plutonium); b) a Fast Breeder Test Reactor; c) a Central Waste Management Facility (CWMF) (which includes concrete trenches where intermediate and high level radioactive wastes are stored); d) an Advanced Technology Vehicle (ATV) Testing Facility (Nuclear Submarine Project); e) a Tritium Extraction Plant; and f) A Sea Water Desalination Plant.

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Nothing has been said about the extent of damage to these facilities and if any radioactive waste

from the Waste Management Facility leaked out. The argument was made that the sitting and design of these facilities were based on the worse historical monsoons and surges that strike the region. Obviously, that was not enough. The risk from a tsunami was completely overlooked, even though several tsunamis generated by earthquakes in the Andaman Sea and along Sumatra have struck India’s east coast in the past. No tsunami risk assessment was ever made.

6b. Need for Proper Building Codes and Engineering A disaster risk assessment study can only provide general guidelines as to what potential impacts

may be at a given location. The job of interpreting the findings of the disaster risk analysis to specific needs for proper building codes and engineering considerations is that of government planners and engineers.

These officials and professionals have the responsibility of adopting proper building codes and the

necessary engineering criteria for new construction and for strengthening codes of existing buildings in disaster vulnerable areas. In some cases protective retrofitting would be relatively simple and inexpensive to do. For example existing buildings in tsunami or hurricane (typhoon) inundation zones can be reinforced to withstand loads expected from the impact of waves and strong currents. Foundations can be constructed or reinforced to resist erosion and undercutting from currents. In some cases the ground floor of oceanfront buildings can be left open to allow flooding or waves to pass through. This helps reduce the undercutting flow around the perimeter of the foundation and can reduce damage. In resort areas such as Phuket in Thailand that was struck by the December 26, 2004 tsunami, if hotel rooms had been built above the second floor guests would have been safer.

Proper engineering is essential to safety and can help minimize losses. For example, buildings are

particularly susceptible to earthquakes and constitute an important factor on how well or badly a community will fare when one strikes. Much collateral damage and injuries can be mitigated with proper engineering design or retrofitting. Therefore, each critical building or structure in areas known to be vulnerable to earthquakes should be examined and evaluated as to the adequacy of its design to withstand the forces of a disaster.

Additional safety could be achieved by redesigning the interiors of existing structures. For

example, essential parts of a building's infrastructure such as emergency generators, power distribution centers, and elevator motors can be located on floors unlikely to flood. Heavy objects such as fuel tanks that may float away and act like missiles can be securely fastened to the ground.

Other critical structures could be similarly examined for safety, damage, or adequacy of design.

For example bridges are strongly affected by earthquakes. Although a bridge may appear to have survived unscathed an earthquake, this does not mean that it did not sustain damage that would culminate to a failure at a later time. Since bridge supports are built along the banks of rivers, it would not be unusual for earthquake liquefaction to move the supports or add extra strain on a bridge’s

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structural components. Therefore, experts and engineers should make a close inspection of all critical structures, even if an earthquake event did not produce obvious damage.

Coastal damage from multiple hazards associated with the August 17, 1999, earthquake on the Gulf of Izmit, Sea of Marmara, Turkey. Hazards included tectonic subsidence, ground liquefaction,

landslides, fires and tsunami. The ship in the foreground was thrown onshore by tsunami wave action. A proper risk assessment study, better land use allocation and zoning and proper engineering design could have mitigated the extent of destruction in this region of the Great Northern Anatolian fault

known for its high seismicity. Up to this time the tsunami hazard in the Sea of Marmara was clearly underestimated. (Photo: Kandilli Observatory and Research Institute (modified))

When dealing with earthquakes, there are many other potential problems for planners and

structural engineers. There are geological challenges pertaining to the specific vulnerabilities unique to each region. There may be various faults and earthquakes may generate seismic waves of different frequencies that may affect a building in an adverse way, depending on its orientation, size, mass, geometry, height and foundations. Design modifications may be necessary to correct for unanticipated forces.

Other disasters present different types of engineering challenges. However the scope of the present

report limits the coverage that can be given. In conclusion, it can be stated that communities that do not perceive they have a potential disaster risk are those that did not invest the time or effort in doing a proper hazard risk analysis or properly inspect building codes and land use policies. Case in point is the devastating tsunami that struck the Indian Ocean countries on December 26, 2004. Up to that time, the officials in the countries of the region did not believe there was risk of a tsunami. The same thing was true in New Orleans. In spite of the looming seasonal hurricane risk, officials erroneously believed that the existing levees would provide protection.

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7. SAFETY PLAN DURING AND AFTER A DISASTER Having developed the means of determining the history, recurrence frequency and simulated

severity of a potential disaster with computer modeling, a risk assessment study must next designate the areas where the adverse impact will be greatest as well as the safe areas - and thus provide a plan for the expeditious evacuation that would ensure the safety of the community during and after the disaster strikes.

The lack of adequate planning for the city of New Orleans became obvious in September of 2005

when hurricane Katrina struck the region. The entire infrastructure of the city collapsed like a house of cards. Conditions became even more dismal for survivors, days after the hurricane was gone. It became clearly obvious that if the response to Hurricane Katrina had been better organized, the devastating impact on the people of the Gulf Coast would have been significantly mitigated. Similarly, recovery in northern Pakistan following the October 8, 2005 destructive earthquake took many weeks. Many more people died from lack of food, shelters and medical treatment.

7a. Post Disaster Recovery Plan: In view of the need for planning, a comprehensive recovery strategy for the post-disaster period

could be part of the risk assessment study or could be adopted subsequently. The post disaster plan must be based on the worse case scenarios that may result from the risk analysis and must provide specific guidelines for the period during and after the disaster.

Additionally, the plan must provide guidelines for uninterrupted functioning of urban infrastructure

facilities and industries, for rescue operations, for medical treatment of those injured, and for shelter and provisions for survivors. Finally, the plan must provide for continuous, longer-term protection to those injured from disease, pollution, exposure to severe environmental conditions, or other post disaster hardships. Food, shelter, clean water, sanitation, and a continuous power supply are prerequisites for rapid recovery following a major disaster.

As already mentioned, the lack of post-disaster relief contributed to the severity of recent disasters.

There were shortages of food, water and supplies when Hurricane Katrina struck New Orleans. It took weeks before some people were evacuated or received medical attention. Many died as a result of inadequate post disaster resources. The same lack of preparedness was evident when the disastrous earthquake struck Northern Pakistan on October 8, 2005 and in the 13 countries that were stuck by the tsunami of December 26, 2004.

In conclusion, rapid, post disaster recovery requires that people in key positions of government

leadership, be trained and prepared, so they can function effectively when a disaster strikes. Additional training may include civil defense exercises at regular time intervals. State and private hospitals should be contacted and urged to participate in the coordination of medical emergencies

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associated with major disasters. Therefore key elements that should be included in a post disaster recovery plan are the required level of preparedness for government officials and the methods and a standard operating plan by which the public could be protected and educated.

Survivors of the October 8, 2005 earthquake in Northern Pakistan waiting for food and medical supplies. (Photo by Captain McDonald Chandi, Salvation Army)

8. DISASTER IMPACT MITIGATION THROUGH PREPAREDNESS AND PLANNING

The safety and security of human settlements in many parts of the world will continue to be

threatened by numerous disasters (Office of the U.N. Disaster Relief Coordinator, 1978). The main reasons are erroneous perceptions of disasters and lack of proper planning and preparedness. Therefore, equally important in mitigating loss of life and damage to property is the identification and perception of potential disasters by the people of each threatened region.

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Disaster perception by the public is based on a technical understanding of the phenomenon, at least at the basic level, and a behavioral response stemming from that understanding and confidence of the public for the authorities to provide safety, timely disaster warnings, and prompt post disaster recovery. Thus, once a disaster risk assessment study has been completed, a program of proper education that promotes disaster awareness and safety rules is an important function of government civil defense authorities.

Lack of preparedness contributed to the suffering of survivors following the devastating earthquake

of October 8, 2005 in Northern Pakistan. Landslides in the mountain region closed the roads. Supplies for relief trickled in by primitive and slow transportation methods.

8a. Public Education

There is a plethora of educational materials and books on all types of disasters and what one needs to know to survive them (American Red Cross, 1983; Blundell, 1977; H. McKinley 1954, Moir, Sunset Magazine). Unfortunately, public education and disaster preparedness - particularly for certain vulnerable regions – is still inadequate. The best and most significant way in minimizing the adverse impact of natural disasters is through public education and understanding on what kinds of problems and other associated hazards can be expected during and after a major disaster. For example, among

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the many misconceptions about the earthquake hazard - one of the commonest - is that only the most destructive earthquakes will kill directly. This is not true. In fact, most deaths are caused by structures falling and collapsing, such as buildings, dams, and bridges. Gas lines rupturing cause fires. Other earthquake related hazards may include landslides, or local tsunamis and such hazards may be more dangerous than the earthquake that caused them.

Based on disaster risk assessments, governmental planners and decision makers, can put

maximum effort in programs of preparedness that focus on educational programs that involve all community agencies, citizens groups, the media, and the school systems. Additionally, they can develop appropriate educational materials, such as brochures and pamphlets, to increase the public’s understanding and awareness on all related natural hazards threatening each specific region and provide safety guidelines on what can be expected and how the direct and indirect effects of the disaster be avoided or minimized.

However, to be effective, disaster education, preparedness and emergency response need to be

continuous efforts and promoted, also, at a grassroots level. Education programs that teach disaster awareness and safety measures should be included in schools, colleges, and places of work.

8b. Disaster Warning Systems A good disaster risk assessment evaluation may also point to the need for a disaster warning

system that could effectively communicate a warning message to the public for proper evacuation from danger areas. Already for certain regions of the world, effective disaster warning systems exist. The Pacific Tsunami Warning System (Pararas-Carayannis, 1978, 1986) and the Hurricane Centers operated by several nations in the Atlantic, the Pacific and Indian Ocean provide early warnings for the respective regions. However, when the great tsunami of December 26 2004 struck 13 countries bordering the Indian Ocean, there was no warning because no operating tsunami warning system existed in this region – although one had been proposed to the United Nations Development Program as early as 1989 (Pararas-Carayannis, 1989). Thousands of lives could have been saved if there was such an early warning system.

Disaster warning systems can drastically reduce loss of life and mitigate destruction of property.

This is not true for some disasters that strike without warning, such as earthquakes. There is no operational earthquake warning systems anywhere in the world. Earthquake prediction is still in the research stage. Furthermore, the only valid earthquake prediction may be the short-term prediction based on some precursor events that may occur in months, weeks, days, or hours before the earthquake strikes. Therefore, such methods are not sufficiently developed to be of value for warning purposes.

For most other disasters there may be a brief cushion of time to issue an early warning. There are

adequate warning systems for tsunamis, hurricanes, surges, tornadoes, mudslides or other weather-related hazards. Volcanic eruptions can usually be forecast by monitoring precursor events. Fortunately the effects of volcanic eruptions are usually localized. Landslides could also be predicted with proper monitoring. Although there is no warning for mudslides, like the deadly one of February

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18, 2006 that struck southern Leyte Island in the Philippines, proper risk assessment and proper land utilization could have mitigated the losses.

There are not established warning systems for other types of disasters. Usually, scientific

institutions and Civil Defense authorities serve as warning centers for other miscellaneous disasters in each threatened region. Early warning systems can save lives. In conclusion, a disaster risk assessment study could support and could provide the justification for the need of high-risk disaster regions to establish early warning systems and programs of public education.

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