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184Natural and human-made disastersBox 7.8 Rapid urbanization and environmental hazard in Dhaka, BangladeshIncreasingly, urbanplanners are lookingfor ways in which …disaster risk-reduction… can scaledown … to semiautonomouslocalplanning and actionzonesDhaka has a population of 11.6 million, and this is rising fast. Thecity is built on alluvial terraces and is exposed to flooding fromrivers, direct rainfall, coastal flooding and earthquakes. With somany sources of natural hazard, one might ask how a city came tothrive 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 designatedthe capital of East Pakistan, with the greatest growth afterindependence when Dhaka became the capital of Bangladesh. In1971, there were between 1 million and 2 million residents.Throughout the modern period, expansion has seen the conversionof marshes and farmland into urban land use. High-rise commercialand residential buildings have become increasingly used to cater forgrowth and are predominantly located in the higher areas of thecity.Despite its long history, 90 per cent of population growthand associated urban expansion into areas at risk has occurredsince 1971. Initial expansion to the north of the city capturedhigher ground above flood levels or on earth-filled lower-lying sites.Source: Huq, 1999be a pressure leading to an increase in vulnerability throughthe lowering of employment rights or environmental protectionlegislation. The 3500 deaths from a toxic gas leak inUnion Carbide’s plant in Bhopal (India) in 1984 can beexplained by just such a cocktail of pressures. 55Urban populations follow industrial investment, sothat large cities also contribute substantially to theircountry’s GDP. For instance, Mexico City is responsible foraround one third of Mexico’s GDP. Large cities and megacities,56 in particular, create huge concentrations of peopleand physical and financial assets, and are frequently alsocultural and political centres. They generate the potential forsubstantial losses from single large disaster events, creatingnew challenges for risk management. Increasingly, not onlythe balance of urban populations, but also the world’s largestcities, will be found in Africa, Asia and Latin America and theCaribbean. 57Not all large urban centres have similar vulnerabilityprofiles. At a broad level, differences exist between thosecities that form part of the core global economy (London,Paris, New York and Tokyo) and are globally connected(Mexico City, Johannesburg, Alexandria and Mumbai), onthe one hand, and, on the other, those that are large but onlyloosely connected globally (Lagos, Nairobi and Khartoum).While this division is simplistic, it serves well to illustratethe different economic base, political institutions andmanagement capacity that is found in large cities andmegacities worldwide.Small cities of less than 500,000 are home to thelarge majority of the world’s urban dwellers, with the totalpopulation of small urban areas exposed to environmentalrisk exceeding the total at-risk population resident in megacities.58 Small cities may be especially susceptible toMore recent expansion has continued northwards over low-lyingland. Inequality is extreme in the city, with the richest 2 per cent ofthe residents occupying 20 per cent of the city’s land. Some 30 percent of the city’s population fall below the poverty line and live inincreasingly marginalized and hazardous slums and squatter settlements.The multiple relationships between urbanization and hazardare well exemplified in Dhaka. Rapid population growth is partlyfuelled by rural migrants who have been made homeless by flooding,cyclones or shifting river beds in rural districts. The neglect ofsmall towns also increases the pull of Dhaka as a place of economicopportunities. Urban expansion in Dhaka is swallowing adjacentagricultural land, reducing opportunities for sustainable local foodproduction.Industrial risk has increased as industrial zones that wereoriginally on the outskirts of the city have been swallowed bysprawling residential areas. These residential zones fall outside ofland-use planning and regulations. Fire is a problem in these areasand in densely populated slum districts.complete destruction in a single event – for example, avolcanic eruption and mudflow in Amero (Colombia) in 1985killed 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, berelocated to avoid hazard risk, this becomes increasinglyproblematic with large cities. There has been some talk ofmoving major cities away from zones of earthquake risk, as inthe case of Tehran, where a large earthquake could claim720,000 lives and bring the country to a standstill. 60 Simplyscaling up risk management procedures developed forrelatively smaller cities might not be the best option forbuilding security into megacities. Increasingly, urbanplanners are looking for ways in which infrastructure, landuseand disaster risk reduction and response planning canscale down from master plans at the city level to semiautonomouslocal planning and action zones. However,experiences of managing disaster risk in larger cities shouldnot be uncritically applied in small urban areas where political,economic, social and environmental contexts andcapacities will differ (see Box 7.9).Even where urban expansion is planned, disaster riskcan be generated. In El Salvador, free trade zones in SanBartolo, El Pedregal, Olocuilta and San Marcos werepromoted by the government without adequate concern forearthquake hazard. During the 2001 earthquake, large losseswere reported from among migrant workers who suppliedlabour to foreign-owned enterprises in these new towns. 61Thus, to understand the motors shaping trends in urbanizationand disaster risk, it is necessary to look beyondpopulation statistics to changes in the form, composition andgovernance of human settlements.