2. In 2006 the world's population
became 50% urban. By 2050
less than 30% will be rural dwellers.
The rich countries are already >75% urban.
3. What does 'urban' mean?
• There is no general definition
or population threshold.
• It implies a certain concentration
of population and services.
• megacity: an urban agglomeration with
a population of more than 10 million.
4. The world’s population is urbanizing
much faster than it is growing.
By 2025 four billion people
will be urban dwellers.
There are 26 megacities
(first five in Asia)
Another ten cities have populations
of more than 5 million inhabitants.
5. Rate of urbanisation in developing
countries is 4%, and 3-5% per year
is the rate of growth of megacities
such as:-
• Dhaka, Bangladesh
• Delhi, India
• Guangzhou, China
• Karachi, Pakistan
• Lagos, Nigeria
6. Megacities may be:-
• megalopolitan areas (megalopolis)
• international urban corridors and axes
• polycentric agglomerations of
connected towns and cities
Dynamic forces:-
• urban sprawl and suburbanisation
• distinction between poor and rich
areas and marginalisation of the poor
• counter-urbanisation into smaller centres.
7. City Country Population Growth rate
Tokyo Japan 34.2 mn 0.6%
Guangzhou China 24.9 4.0
Seoul South Korea 24.5 1.4
Delhi India 23.9 4.6
Mumbai India 23.3 2.9
Mexico City Mexico 22.8 2.0
New York City USA 22.2 0.3
São Paulo Brazil 20.8 1.4
Manila Philippines 20.1 2.5
Shanghai China 18.8 2.2
8. Large cities constitute the greatest
concentrations of natural hazard risk
and are poles of attraction for
other kinds of disaster risk.
Urbanization, perhaps even
metropolitanization, is one of the
principal factors that is propelling
the world-wide rise in disaster losses.
9. In places like Port au Prince, Haiti,
and Luanda, Angola, the status
quo ante has often seemed as bad
as any disaster impact.
11. Post-disaster urban reconstruction
• damaged assets can seldom be
rebuilt to the original standards
• reconstruction must take account
of new norms and requirements
• reconstruction requires more space.
12. Increasing reliance of urban hazard
managers on technological systems
in order to reduce risk - a general
characteristic of municipal and
regional hazard management.
23. Challenges to DRR posed by megacities:-
• scale and geographical complexity
• environmental impact
and resource consumption
• hazardous locations (especially coastal)
• sensitive to climate change effects
• many megacities are home to the vast
slums of the poor and marginalised.
24. Conclusions
• Well-established parts of cities
may slowly have developed
resilience against hazards.
• Urban sprawl may take cities
into unstabilised hazard zones.
• Environmental discrimination relagates
the poor and marginalised to the
least safe urban environments.
• megacities are vast urban systems
with equally huge vulnerabilities.
• Sustainability is a general issue for them.
