Global Report on Human Settlements 2007 - PoA-ISS

184
Natural and human-made disasters
Box 7.8 Rapid urbanization and environmental hazard in Dhaka, Bangladesh
Increasingly, urban
planners are looking
for ways in which …
disaster risk-reduction
… can scale
down … to semiautonomous
local
planning and action
zones
Dhaka has a population of 11.6 million, and this is rising fast. The
city is built on alluvial terraces and is exposed to flooding from
rivers, direct rainfall, coastal flooding and earthquakes. With so
many sources of natural hazard, one might ask how a city came to
thrive in such a location.
The city’s growth has been tied to its political importance.
The city was established as the capital of Bengal in 1610. In 1905,
Dhaka became the capital of East Bengal and in 1947 it was designated
the capital of East Pakistan, with the greatest growth after
independence when Dhaka became the capital of Bangladesh. In
1971, there were between 1 million and 2 million residents.
Throughout the modern period, expansion has seen the conversion
of marshes and farmland into urban land use. High-rise commercial
and residential buildings have become increasingly used to cater for
growth and are predominantly located in the higher areas of the
city.
Despite its long history, 90 per cent of population growth
and associated urban expansion into areas at risk has occurred
since 1971. Initial expansion to the north of the city captured
higher ground above flood levels or on earth-filled lower-lying sites.
Source: Huq, 1999
be a pressure leading to an increase in vulnerability through
the lowering of employment rights or environmental protection
legislation. The 3500 deaths from a toxic gas leak in
Union Carbide’s plant in Bhopal (India) in 1984 can be
explained by just such a cocktail of pressures. 55
Urban populations follow industrial investment, so
that large cities also contribute substantially to their
country’s GDP. For instance, Mexico City is responsible for
around one third of Mexico’s GDP. Large cities and megacities,
56 in particular, create huge concentrations of people
and physical and financial assets, and are frequently also
cultural and political centres. They generate the potential for
substantial losses from single large disaster events, creating
new challenges for risk management. Increasingly, not only
the balance of urban populations, but also the world’s largest
cities, will be found in Africa, Asia and Latin America and the
Caribbean. 57
Not all large urban centres have similar vulnerability
profiles. At a broad level, differences exist between those
cities that form part of the core global economy (London,
Paris, New York and Tokyo) and are globally connected
(Mexico City, Johannesburg, Alexandria and Mumbai), on
the one hand, and, on the other, those that are large but only
loosely connected globally (Lagos, Nairobi and Khartoum).
While this division is simplistic, it serves well to illustrate
the different economic base, political institutions and
management capacity that is found in large cities and
megacities worldwide.
Small cities of less than 500,000 are home to the
large majority of the world’s urban dwellers, with the total
population of small urban areas exposed to environmental
risk exceeding the total at-risk population resident in megacities.
58 Small cities may be especially susceptible to
More recent expansion has continued northwards over low-lying
land. Inequality is extreme in the city, with the richest 2 per cent of
the residents occupying 20 per cent of the city’s land. Some 30 per
cent of the city’s population fall below the poverty line and live in
increasingly marginalized and hazardous slums and squatter settlements.
The multiple relationships between urbanization and hazard
are well exemplified in Dhaka. Rapid population growth is partly
fuelled by rural migrants who have been made homeless by flooding,
cyclones or shifting river beds in rural districts. The neglect of
small towns also increases the pull of Dhaka as a place of economic
opportunities. Urban expansion in Dhaka is swallowing adjacent
agricultural land, reducing opportunities for sustainable local food
production.
Industrial risk has increased as industrial zones that were
originally on the outskirts of the city have been swallowed by
sprawling residential areas. These residential zones fall outside of
land-use planning and regulations. Fire is a problem in these areas
and in densely populated slum districts.
complete destruction in a single event – for example, a
volcanic eruption and mudflow in Amero (Colombia) in 1985
killed most of the city’s 25,000 inhabitants. 59 Despite this,
the majority of research and investment have, to date,
focused on large cities and megacities.
While smaller settlements might, as a last resort, be
relocated to avoid hazard risk, this becomes increasingly
problematic with large cities. There has been some talk of
moving major cities away from zones of earthquake risk, as in
the case of Tehran, where a large earthquake could claim
720,000 lives and bring the country to a standstill. 60 Simply
scaling up risk management procedures developed for
relatively smaller cities might not be the best option for
building security into megacities. Increasingly, urban
planners are looking for ways in which infrastructure, landuse
and disaster risk reduction and response planning can
scale down from master plans at the city level to semiautonomous
local planning and action zones. However,
experiences of managing disaster risk in larger cities should
not be uncritically applied in small urban areas where political,
economic, social and environmental contexts and
capacities will differ (see Box 7.9).
Even where urban expansion is planned, disaster risk
can be generated. In El Salvador, free trade zones in San
Bartolo, El Pedregal, Olocuilta and San Marcos were
promoted by the government without adequate concern for
earthquake hazard. During the 2001 earthquake, large losses
were reported from among migrant workers who supplied
labour to foreign-owned enterprises in these new towns. 61
Thus, to understand the motors shaping trends in urbanization
and disaster risk, it is necessary to look beyond
population statistics to changes in the form, composition and
governance of human settlements.