Because mega-cities are a relatively recent phenomenon, the literature on mega-city disasters is sparse. Much more is known about the relationship between natural disasters and urbanization in general.
Despite some tendencies towards uniformity and homogenization, there is a great deal of variety among mega-cities and considerable uncertainty about their eventual dimensions. Different types of mega-city are likely to have quite different disaster-susceptibilities and different capabilities for response. Mega-cities may grow, becoming both more complex and more alike. Or there may be perhaps two or three basic variants.
For example, if the organization of the global economic, and political system continues to be dominated by a relatively few countries, it may well be that the natural hazard profiles of mega-cities in the dominant (rich) countries will continue to diverge from those of the (poor) rest, thereby rendering problematic the exchange of hazard experience and hazard-reduction technologies between both. On the other hand, there is evidence that some of the characteristics of third world cities are beginning to show up in places such as Los Angeles and Miami, thus raising the possibility of eventual re-convergence.
Both in rich and poor countries, the growth of such giant urban agglomerations possess major metropolitan planning problems which must be solved in a broad regional context. Food, fuel, electric power, and drinking water must be brought in from considerable distances, and massive quantities of waste materials must be disposed off.
The giant metropolis needs very sophisticated transportation systems if it is to function effectively, and city dwellers may have to travel considerable distances to recreational facilities and surviving farm and wilderness areas. Most major cities also have some special problems resulting from the peculiarities of their sites, for example subsidence, earthquakes, and air and groundwater pollution buildups in Mexico City, and flooding and typhoon damage in Dacca.
Large cities of antiquity certainly experienced heavy losses as a result of natural disasters, but the data are highly incomplete. Chandler and Fox (1974) show that at least a score of cities each recorded tens of thousands of deaths in the wake of earthquakes, floods, volcanic eruptions, and other events. But few of these places had populations that exceeded 200,000 and most were considerably smaller.
The Tokyo-Yokohama metropolitan area was probably the first mega-city to be devastated by a natural disaster. The Great Kanto earthquake (1923) killed approximately 100,000 people in Tokyo and destroyed more than 700,000 houses in a city of over 2 million. In the half-century between 1945 and 1995, around 100 natural disasters affected large cities.
The most physically destructive single events during this period took place in – Nagoya (typhoon, 1959), Tangshan (earthquake, 1976), Bucharest (earthquake, 1977), Mexico City (earthquake, 1985), Miami/Dade County (hurricane, 1992), and Kobe (earthquake, 1995). Latest to add is Mumbai (rainflood, 2005). However, a focus on great catastrophes may be misplaced, because the aggregate impacts of lesser events can be much larger.
This is particularly so in third world mega-cities, where small storms, floods, and seismic shocks, events that would be considered inconsequential elsewhere, often wreak disproportionately heavy losses. In such places, natural hazard is a more or less chronic everyday problem. Earthquakes, severe storms, and wildfires appear to be the most frequent catastrophic urban events.
It is worthwhile noting that urban areas are the sites of many different types of disaster – natural, technological, biological, and social. Thus far, most of these have been simple events of one type, but compound events that involve two or more of these components are beginning to appear (e.g. floods that disperse toxic materials, earthquakes that rupture oil pipelines and storage tanks, droughts that uncover flooded waste disposal sites). The potential for further “surprises” is obvious.
Of late it has been noticed that rapid large-scale urbanization is a major contributor to the rising global toll of disaster losses. The world’s big cities are rapidly becoming more exposed and more vulnerable to natural hazards and disasters. Unfortunately, the special problems of urban disasters have not received much attention from scholars and professionals.
“Too much of our efforts to assist… for too long have been focused on rural populations which are of ever diminishing relative magnitude and importance”. Much of the most useful information on urban disasters is part of a “grey literature” that is not readily available to potential users.
During the 1990s a number of researchers addressed the intersecting problems of cities and disasters. One of these was the disaster relief expert Frederick Cuny, whose strong convictions about the pivotal role of cities in international disaster operations began to appear in print just before his disappearance and probable murder in Chechnya.
Other notable contributions during this period include Sylves and Waugh’s (1990) case-studies of emergency operations in American cities; Zelinsky and Kosinski’s (1991) valuable compilation of data on urban evacuations; Berke and Beatley’s (1992) analysis of earthquake planning in midsized US cities (Salt Lake City, Palo Alto, Charleston); a path-breaking edited collection of papers by geographers on housing and hazards in cities in less developed countries (Cairo, Bhopal, Mexico City, Agadir, Caracas, Hong Kong); a special issue of a European geography journal that focuses on geological hazards in mountain cities (Revue de Geographic Alpine, 1994); and the proceedings of a workshop on urban hunger in developing countries organized by the International Geographical Union’s Commission on Vulnerable Food Systems.
The headquarters staff of the UN-sponsored International Decade for Natural Disaster Reduction (1990-2000) has also published a slim volume that reviews projects designed to improve urban disaster mitigation in 11 different countries and supplies information about organizations that are active in this field (IDNDR, 1996).
Though all of these publications deal with hazards and disasters in exclusively urban settings, none focuses specifically or exclusively on large cities. Recent works with a more explicit focus on mega-city hazards include collections of papers prepared by contributors to a World Bank-sponsored conference and by members of the International Geographical Union’s Study Group on the Disaster Vulnerability of Megacities. In addition, the UK Institution of Civil Engineers has published a report on mega-city vulnerability (Institution of Civil Engineers, 1995).
Due to the likely impact of natural disasters on mega- cities is so great and so little understood, “the vulnerability of mega-cities” was identified as a high-priority topic for research and action during the International Decade for Natural Disaster Reduction (IDNDR). A major effort in support of that theme was mounted by the global scientific and technology community under the auspices of the International Council of Scientific Unions (ICSU).
At ICSU’s invitation, the International Association of Engineering Geologists and the World Federation of Engineering Organizations were encouraged to bring together a variety of academic and professional groups with the objective of formulating a collaborative agenda for mega-cities and disasters.
This included projects by the UK Institution of Civil Engineers and the International Geographical Union as well as the World Bank and Habitat, among others. Independent but related programmes were also organized by the global community of landscape architects and other professional bodies. Most of these activities involve organizations of scientists, engineers and urban managers.
The intellectual principle on which the IDNDR rests is a well-founded recognition that society already possesses a great deal of valuable information about the reduction of natural disasters but has largely failed to put that information to appropriate use. For most of the scientific and engineering community the main task is to apply existing knowledge about disaster reduction to a series of specific contexts – in this case, mega-cities.
It is assumed that, like Archimedes, managers can stand on the stable base of accumulated technical knowledge and engage the lever of science to “move” the world of urban disasters. Undoubtedly, if resolutely followed, this strategy will produce important benefits, especially when it results in genuine partnerships between the producers and users of scientific information.
For a student of natural hazards, the city is but one among many physical settings of extreme events, albeit a setting that usually makes few concessions to the natural systems that are the agents of disaster. Conversely, from the perspective of urban managers, natural disasters are just one among many problems that must be confronted within city boundaries – and an infrequent one, at that Hazard management has a place in the spectrum of urban issues but that place must be negotiated among competing demands for attention to other problems (e.g. new urban in-migrants, decaying infrastructure, poor housing, hazardous facilities, deindustrialization, pollution, homelessness, lack of mass transit, street crime, inadequate social services, ethnic and racial tensions).
Nor is it simply that natural disasters must compete with other urban issues for public attention; they are intimately bound up with those issues. For example, the flood and landslide disasters of Rio de Janeiro, Caracas, and Tijuana are closely connected to problems of obtaining affordable housing faced by poor migrants from rural areas. Prospects for earthquake hazard reduction in Tokyo are affected by the high cost of urban land, which encourages crowded neighbourhoods, restricts open space, and pushes new developments onto hazard-susceptible low-lying filled land in Tokyo Bay.
The protection of Kolkata or Lagos against flooding is also tied up with inadequate means for disposing of solid wastes, antiquated or non-existent sewage systems, and budgetary conflicts between the city and national governments.
The fragmentation (“de-urbanization”) of metropolitan populations and governments has a significant bearing on the design and operation of hazard-management systems in mega-cities of the United States (e.g. Los Angeles, Miami) and other developed countries. The implications are clear. If natural disasters are to be reduced in a big-city setting, the Archimedean metaphor of science-driven solutions is not an appropriate guide.
Urban disasters are not merely a kind of inert problem that will yield to the direct application of scientific knowledge -they push back In other words, not only do disasters affect cities but urbanization affects the creation of vulnerability, the scope for mitigating action and a wide range of related topics. Thus, no doubt urbanization provides an interactive context for disaster.
There is one further twist to the relationship between disasters and mega-cities — perhaps the most important factor of all. Both elements of the problem – cities and disasters – are now changing in complex ways. The nature of disasters is changing- new kinds are emerging – some of them unprecedented. The management of disasters is changing in many countries, existing institutions and policies are coming under increased criticism and there are calls for new ones.
The ways we think about disasters are changing: for example, a post-modernist dialogue is beginning to appear in the professional literature. Equally, the nature of cities is changing: not only are they more numerous, bigger, and non-Western, but their economic and cultural functions are in flux, casting previous models of urban development into doubt.
The management of cities is changing- pressed from below by burgeoning demands from their rapidly growing and diversifying populations, governments of mega-cities are also shifting to adjust to other pressures such as the changing role of national governments in the face of global economic integration and the reluctance of those governments to honour existing commitments to assist the cities.
Urban mass movements and emergent neighbourhood organizations are also exerting pressure for the “reinvention” of mega-city governments. As big cities become increasingly important actors on the world stage, their populations are drawing on the experience of peer cities beyond national boundaries. As a response to such changes, it is no surprise that the intellectual basis of urban analysis is also in flux.
Under such circumstances, the Archimedean metaphor requires further modification. Not only are the problem spheres of disasters and urbanization interactive (i.e. urban disasters “push back”), but given the speed and scope of changes that are now afoot in botii spheres there may no longer be a truly stable base from which the leverage of scientific knowledge can be pivoted.
This means that taken-for-granted assumptions about scientific information and disaster reduction need to be critically examined in light of the highly changeable contexts that bracket both disasters and mega-cities. Until these contexts are better known, the transfer of knowledge and technology among countries and cities should proceed with caution. Mega-city disaster-reduction initiatives will have to be carefully tailored to local conditions and specific settings.
In coming to grips with the complexities of a dynamic set of relationships between mega-cities and natural disasters it may be helpful to think in terms of a contextual model. Such a model is intended to show how a more or less discrete process relates to the broader environment of which it is a part.
The central process is one of hazard and the larger context is that of urbanization. Both components of the model can be considered separately and in conjunction. The hazard component includes four main elements- physical processes, human populations, adjustments to hazard, and net losses.
As people seek to adjust to hazardous natural environments, these four elements modify each other through seven endogenous feedback relationships. A change in one or more elements may set in motion a cascade of reflexive changes in the others.
The stimulus for change may be some or all of the following- an extreme natural event such as an earthquake or a storm; community encroachment into an area of known hazard; urban technologies that inadvertently alter existing physical risks; the development of vulnerable groups, institutions, or technologies; the adoption of specific new hazard-management measures and the decay of old ones; and a broad-based commitment to raise general thresholds of public protection against hazards of various kinds.
Change can also come from outside the hazard system. That context includes exogenous factors or processes that interact with components of hazard, but are largely independent of them. These include variables such as the stages of city development (including the growth of mega- cities), the internal structure and functioning of urban areas under different sociocultural, political, and economic systems, and the urban implications of a wide range of contemporary changes in science, technology, environment, economics, politics, and culture.
Among the latter are – the flow of new scientific information and the diffusion of new technologies; the growing recognition that humanity now has the capability to affect environmental change on a global scale; worldwide economic restructuring and integration; the collapse of an existing international geopolitical order and the development of replacement arrangements (e.g. continental trading blocs, ethnically fragmented states, “reinvented” governments, nongovernmental organizations, urban mass movements); and the adoption of “post-modern” modes of thought and action both within the intellectual community and beyond.
In the same way that a viewer can construct different interpretations of an illusion by focusing on either the figure or the ground, it is possible to arrive at an explanation of urban disasters that depends on disaster agents and proximate human responses or to fashion an explanation around the distal structuring characteristics of urban systems and urban lifeway’s.
The latter approach may redefine the meaning of disaster in an urban setting and predispose cities to “disasters” that are different from those natural scientists customarily think of. But urban disasters are not just amalgams of disaster and urbanization; they are the products of a set of changeable relations between both components. This feature makes it difficult to fashion effective programmes of urban disaster reduction by employing only the perspectives on hazards management or urban management.
The permutations of natural hazard and urbanization produce different outcomes in different settings at different times. Moreover, the set of possible permutations is significantly larger than the set of outcomes to date; an understanding of this fact opens up a vast untapped potential for intervention to make cities safer places.
Evidence of increasing disaster-susceptibility in mega-cities bespeaks a change in the balance of hazard and opportunity in urban life. Of course changes in the mix of urban hazards and shifts in the hazard-opportunity balance have gone on throughout history. For several centuries the balance has tilted steadily towards higher levels of safety and opportunity for most city residents, while hydrological, meteorological, and geological hazards have declined relative to other types of threat.
Urban concentrations of wealth, knowledge, talent, and power have justified and made possible extraordinary efforts to protect people and property against the more obvious extremes of Nature. The avoidance, prevention, and mitigation of natural hazards were a primary responsibility of those who ruled the ancient cities of Egypt, China, and Central America.
Dyking, drainage, and irrigation schemes were among the earliest urban public works in these places. The suppression of fire was a high priority in the crowded cities of medieval Europe and elsewhere at other periods. A widely shared commitment to protect urban lives and property against natural extremes continues today.
Contemporary Japanese cities are showplaces of hazard engineering, the metropolitan areas of Rotterdam and London are flanked by some of the world’s most modern and technologically advanced flood defences, Mexico City has invested in the world’s only public earthquake alarm system (New York Times, 19 December 1993), and the vast drainage network of greater Los Angeles has been so extensively modified by humans that it is now an almost totally artificial construct.
Heightened urban sensitivity to hazards and the benefits of hazard reduction do not mean that big cities have been – or are – entirely safe from extreme natural events. Nor do they mean that cities have been free of other types of hazard. (The historical record of urban epidemics, riots, fires, industrial accidents, and similar social ills is salutary.) But, over the long run, it is clear that a quite remarkable record of success has attended efforts to provide many urban dwellers with improved security against geological, meteorological, and hydrological hazards.
Now there is growing concern that cities are becoming so numerous, so large, so complex, and so volatile that the balance between risk and reward will tilt back towards conditions of increased natural hazard in the absence of determined efforts to reverse that trend. A world of mega- cities may well be more risky, more exposed, and more vulnerable than the world we currently inhabit.
The scale of potential mega-city losses imposed by floods, storms, earthquakes, and other phenomena compels attention to the problem. So too does the timing, for we are fast becoming a predominantly urban world, a world where half the urban population will be citizens of mega-cities.