The special case of Mega-cities

At 7:17 a.m. on 19 September 1985, an earthquake struck Mexico City - the largest city in the Americas and the second largest in the world, after Tokyo. It lasted a minute and a half, and measured 8.1 on the Richter scale.

More than 9,500 lives were lost, and about $4 billion of damage occurred in a city where approximately 26 million people live today. Over 400 buildings collapsed and seven times that were seriously damaged. More than 100,000 people were left homeless.

Natural disasters are more destructive when they strike large cities, given the growing trend of high urban-population densities. In addition, increasing numbers of people living in informal, unsafe settlements make ever-larger cities more vulnerable to naturally occuring hazards.

However, preventing – or limiting - the damage caused by earthquakes, floods and fires requires that urban-disaster mitigation be tailored to the specific risks that urban settlements face. Construction needs to be regulated and safety standards enforced – especially with informal housing, which is the fastest-growing type of human settlement.

Ensuring that slums are not hardest-hit, let alone exposed in the first place, requires that serious urban-governance issues be tackled, namely the decentralisation of decision-making.

As urbanisation accelerates, and cities expand endlessly, the adoption of urban disaster-risk reduction strategies is literally becoming a matter of life and death.

The “mega-city” trend

Urbanisation, the exodus from rural areas to cities, will be a major demographic phenomenon of the 21st century, according to experts.

Whereas in 1950 only about 30 percent of the world’s population lived in cities, the United Nations Human Settlements Programme (UN-HABITAT) currently puts that figure at 50 percent. It is expected to rise to more than 60 percent by 2030.

The trend of urbanisation is both accelerating and irreversible. UN-HABITAT forecasts that, “over the next two decades, 90 percent of population growth in developing countries will be urban.” This unprecedented explosion of municipal communities poses unique challenges to city planners in terms of disaster-risk reduction policies.

Mega-cities, a term coined in the 1970s by the United Nations to define urban settlements of eight million inhabitants or more, are particularly at risk. Currently, 280 million people live in at least 25 mega-cities across the world, three-quarters of which are located in the developing world. This figure is expected to rise to 350 million by 2015.

Of the 15 largest mega-cities, only four are located in highly industrialised countries: Tokyo, New York, Los Angeles, and Osaka-Kobe-Kyoto. The overwhelming majority of mega-cities are located in developing countries, and include such gigantic conurbations as São Paulo (17.9 million inhabitants in 2000), Delhi (14.1 million), and Manila (13.9 million).

Paradoxically, repeated natural disasters in rural areas are a major factor driving populations to cities. But most of today’s mega-cities are built in areas where earthquakes, floods, landslides and other natural disasters are most likely to happen.

The greater the density, the greater the vulnerability

Natural disasters in mega-cities are likely to cause large numbers of casualties because of the high demographic density in urban areas. Many of the casualties when a natural hazard – a flood, earthquake or fire - strikes a mega-city are due to the collapsing of buildings and other infrastructure which were designed for large numbers of residents.

In January 1995, the Great Hanshin-Awaji earthquake, which struck the Japanese city of Kobe, home to 1.5 million residents, cost more than US$ 100 billion. The density of the city’s settlements and population not only caused high human casualties – more than 6,000 died – but was also a major impediment to rescue and relief operations attempting to access victims. Infrastructure supplying water, electricity and gas was destroyed, further impeding response efforts.

High concentrations of people and buildings mean that even moderate disasters can lead to heavy human losses.

Esteban León, disaster-management specialist for UN-HABITAT, thinks prevention is the answer. “Numbers of inhabitants are not the problem - you can have cities with high concentrations of people and avoid high casualties when disaster strikes. That is due to effective prevention,” he explained to IRIN.

“No one can prevent natural phenomena from happening. Think of trying to prevent the rain from falling. What you can do is prevent it from becoming a disaster – you won’t get wet if you thought of carrying an umbrella,” he added.

The danger of poverty

Unfortunately, most mega-cities are located in developing countries, with few financial or human resources to allocate to natural-disaster-risk reduction. The lack of urban-planning capacity often explains additional urban risk factors, such as badly designed or poorly constructed buildings and infrastructure.


Hydro-meteorological natural disasters are more frequent than even: visiting disproportionately higher damage on poorer communities more than developed countries where risk reduction and early warning measure exists and where property is insured.
Credit: AFP

The quality of housing construction and infrastructure is therefore essential to reducing disaster vulnerability in urban environments.

This is the main reason why natural disasters disproportionably affect the poor. Poorer sections of urban populations often live in high-risk locations, such as steep or unstable hillsides and unclaimed terrain, which are especially prone to natural hazards. The poor build cheap, reside in the most unsafe settlements, and are the first at risk.

Bam makes a good example of this. The earthquake which struck the Iranian town, home to around 200,000 people, on 26 December 2003, demolished approximately 25,000 houses, according to UN figures.

Most houses in the region were built with mud bricks – not earthquake-resistant reinforced concrete - accounting for the extreme vulnerability of the settlement to seismic activity.

According to the US Geological Survey, the earthquake measured 6.7 on the Richter scale and lasted 20 seconds. Local reports estimated that between 70 percent and 80 percent of the town’s buildings were destroyed.

More than 42,000 of Bam’s residents were killed. Although no mega-city, the proportion of fatalities compared to total population (more than one-fifth) is a reminder of what can happen when hazards hit populous, underdeveloped areas.

Regulating construction

UN-HABITAT defines disaster mitigation as “sustained actions to reduce or eliminate the impacts and risks associated with natural and human-caused disasters.”

In the case of urban settlements, this means first and foremost creating and adopting adequate construction regulations.

Construction codes must specify proper building materials and procedures. Land-tenure codes must ensure residents have an interest in making their settlement safer, and that they are included in disaster-management efforts.

Building regulations must be effectively enforced, to ensure builders and suppliers are accountable by these standards. But enforcement of such norms is often limited by corruption and a lack of trained personnel.

Risk education

Most city dwellers are not conscious of the risk of natural hazards they face, or how to prevent them. Raising awareness among potential disaster victims is essential.

This is especially true for the masses of rural migrants recently arrived in unfamiliar cities, and for, again, the poor, who are have received less education.

The perception of what constitutes risk varies from country to country, and urbanisation weakens traditional coping mechanisms. Inter-personal links, family ties and village solidarity, which are relied upon in times of hardship in rural areas, disappear in the big cities. The hazards faced in cities are also different from the ones rural inhabitants are used to.

Disaster-risk awareness can be incorporated into school curriculums, as well as the agendas of residents’ associations and community-based organisations.

Disaster-management experts often regret the fact that media coverage of disasters essentially focuses on post-impact relief and response, and rarely on preventive measures.

Preventing disasters requires timely and accurate dissemination of information resulting from real-time hazard-data collection. Early-warning systems must be accessible to all.

Technologies like “geocoding”, used by private insurance companies to underwrite disaster insurance premiums in cities, convert addresses into geographical longitudes and latitudes, and make a risk assessment for that area. This allows critical areas to be identified within mega-cities, and risk management to be improved.

However, despite the fact that some of the tools used by the private sector to assess vulnerabilities could significantly reduce the risk of disasters, private insurance tends to be the prerogative of highly developed countries.

Microfinance is already a feature of disaster-risk reduction initiatives in some rural areas, allowing farmers to pool resources to get insurance coverage. It has, however, hardly spread to the urban context. Public-private partnerships could also contribute to hedging urban risks, by bringing together finance and governance experience.

Political decision-makers should also be targeted by sensitisation efforts. León deplores current approaches in the field, as illustrated by recent efforts to assist victims of the December 2004 tsunami that left millions homeless.

“Donors do not prioritise shelters and long-term infrastructure when responding to emergencies,” he said. “The funding goes to water, sanitation and food-relief efforts, but not to building proper, disaster-resistant shelters,” he added.

Decentralising relief efforts

Decentralising disaster-risk reduction initiatives down to local urban authorities is essential for accurate and timely monitoring, as well as for disaster prevention and response.


Urban agglomerations like Tokyo and Mexico city and many others are highly complex major risks, which present the inhabitants, politicians and the insurance industry with huge challenges.

Local communities and civil society are the first line of disaster management. A participatory approach is crucial in defining disaster-risk reduction policies and actions. Local residents and their representatives should lobby governments for improved safety conditions – they hold central and local institutions accountable.

A strong and vibrant civil society is therefore the cornerstone of disaster-risk reduction strategies.

Central governments can help local decision-makers build capacity. But some things can only be carried out effectively at a local level: creating strong commitmenst to alleviate disasters; enforcing building and planning regulations; and implementing prevention and response schemes.

South Africa’s National Disaster Management Act of 2002 clearly defines the roles of actors at national, municipal and regional levels. Even though it states that “the primary responsibility for disaster management in South Africa rests with the government”, it ensures that “local government is also empowered to deal with a number of functions that are closely related to disaster management”.

Decentralising disaster management is essential. Governments come and go, but institutional memory – the assimilation of best practices and lessons learned from past experience – must be reinforced to face irregular, but recurrent, hazards.

Slums: first exposed, hardest hit, least helped

In the majority of cases, migrants who move to cities in search of safety and livelihoods will end up in informal and unsafe settlements.

UN-HABITAT figures for 2004 show that a quarter of the world’s urban population does not have adequate housing.

More than 900 million people across the globe live in slums, which the agency defines as “contiguous settlement[s] where the inhabitants are characterised as having inadequate housing and basic services. A slum is often not recognised and addressed by the public authorities as an integral or equal part of the city.”

Wild, unregulated urbanisation stretches a city’s capacity to minimise residents’ exposure to disasters before they happen, and to assuage the effects of hazards after they occur.

Poor planning, bad and illegal construction practices and ecological exploitation of the environment are additional vulnerabilities that threaten slum dwellers.

Poor households often have no choice but to “build cheap”, and are therefore the first at risk in the event of a catastrophe.

Communities residing in “marginal settlements” have little incentive to invest in housing standards, given that they do not have secure tenure. Why spend scarce financial resources on upgrading a home you can never own?

Most slum residents are not legally entitled to settle where they do. When disaster-risk reduction strategies exist, they rarely apply to illegal tenures.

Mumbai, India, is a mega-city of more than 20 million people. Over 90 percent of its inhabitants squat in informal settlements, and construction standards specify seismic norms for government buildings only. Private housing – even legal - is not subject to earthquake-resistant construction norms.

In some instances, urban governance can be an additional agent of disaster, as slum dwellers face higher chances of being evicted from their settlement if they improve its safety, because they have made it more valuable.

Impediments to disaster-risk reduction

Poor governance, such as bad city-planning and weak public institutions, increases urban vulnerability to natural hazards.

Many developing countries do not have permanent agencies or facilities for disaster-risk reduction. They are, however, often the most exposed to natural disasters. Africa, for instance, is the continent that experiences the most rapid urban growth.

More generally, governments tend to emphasise short-term results. A widespread culture of prevention is lacking. In a context where public resources are scarce, disaster-management decisions and actions are often influenced by political considerations, regardless of real-life vulnerabilities.

According to León, “disaster prevention is more than actions, it’s a process, a way of thinking that has to be acquired.”

Institutional culture may be the first obstacle to the implementation of effective disaster-risk reduction strategies in mega-cities. But mindsets change slowly, and old habits die hard.