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close this bookCrucibles of Hazard: Mega-Cities and Disasters in Transition (United Nations University, 1999, 544 p.)
View the document(introduction...)
View the documentAcknowledgements
View the document1. Introduction - James K. Mitchell
View the document2. Natural disasters in the context of mega-cities - James K. Mitchell
View the document3. Urbanization and disaster mitigation in Tokyo - Yoshio Kumagai and Yoshiteru Nojima
View the document4. Flood hazard in Seoul: A preliminary assessment - Kwi-Gon Kim
View the document5. Environmental hazards in Dhaka - Saleemul Huq
View the document6. Natural and anthropogenic hazards in the Sydney sprawl: Is the city sustainable? - John Handmer
View the document7. Disaster response in London: A case of learning constrained by history and experience - Dennis J. Parker
View the document8. Lima, Peru: Underdevelopment and vulnerability to hazards in the city of the kings - Anthony Oliver-Smith
View the document9. Social vulnerability to disasters in Mexico City: An assessment method - Sergio Puente
View the document10. Natural hazards of the San Francisco Bay mega-city: Trial by earthquake, wind, and fire - Rutherford H. Platt
View the document11. There are worse things than earthquakes: Hazard vulnerability and mitigation capacity in Greater Los Angeles - Ben Wisner
View the document12. Environmental hazards and interest group coalitions: Metropolitan Miami after hurricane Andrew - William D. Solecki
View the document13. Findings and conclusions - James K. Mitchell
View the documentPostscript: The role of hazards in urban policy at the millennium - James K. Mitchell
View the documentAppendices
View the documentContributors
View the documentOther titles of interest

9. Social vulnerability to disasters in Mexico City: An assessment method - Sergio Puente

Editor's introduction

Mexico City is a testament to the durability of environmental hazards in many parts of the world. Successive cultures that occupied this site, from the pre-Aztec to the post-colonial, have faced demanding constraints of seismicity, vulcanicity, subsidence, aridity, flooding, and altitude and have adjusted with different degrees of success. All have either made careful allowances for these hazards in the design and operations of their communities or been forced to take them into account retroactively. But none has had to cope with such an explosive expansion of population and urban development as has occurred in the late twentieth century. As a result, instead of drawing on reliable mechanisms of urban society to buffer themselves from environmental risks, modern residents of Mexico City occupy an uncertain, often provisional, metropolis. Dizzying growth and deep-seated social dislocation challenge inherited ways of thinking and acting about environmental risk and foster the emergence of new hazard-management approaches. This is a situation that calls for sensitive handling and enlightened analysis, a challenge to which Sergio Puente's paper directly responds.

[T]he Aztecs and the tribes that preceded them did not believe that their valley had attained physical stability. Their religion was filled with prophecies that the world would be torn asunder by cataclysmic earthquakes. The Spanish conquistadors witnessed volcanic activity in the crater of Popocatepetl... In 1985, thousands of Mexico City residents perished and hundreds of buildings were destroyed by a giant quake. And dozens of times every year, the capital's inhabitants experience the stomach-churning sensation of smaller tremors that cause no damage but remind the populace that the earth beneath their feet is unsettlingly alive.

(Kandell, 1988, pp. 10 - 11)

Mexico must stop acting as if Mexico City were some sort of natural disaster out of control.

(Vargas, 1995)

Introduction

Vulnerability can be defined as the propensity to incur loss. The disaster-vulnerability of urban areas is not exclusively determined by human factors but, during the twentieth century, the human contribution has come to dominate. This is partly a result of profound worldwide social and technological transformations that have concentrated population and industry in cities. It is also an outgrowth of other broad societal changes that raise serious questions about the proper role of humankind in a changing world. These include: a breakdown of existing relationships between society and nature; crises of economic development and world order; and pressures to redefine the societal roles of science and technology. To resolve problems of environmental hazard in cities it may be necessary to modify fundamental aspects of society, including the human axiological system.

The mega-city as locus of hazard

It has been argued that natural events become natural disasters because humankind is preoccupied with the goal of economic growth to the exclusion of sensible precautions for human safety. From this perspective, the city represents the maximum human appropriation of Nature (Ibarra, Puente, and Schteingart, 1984). By spatially concentrating many activities of social reproduction, the city also concentrates risks that are inherent in its location and the indifference of its residents to natural processes. Because mega-cities usually contain the largest concentrations of population and economic activities, they may well be the loci of highest risk and greatest exposure to natural disasters.


Fig. 9.1. Mexico: Distribution of cities with more than 100,000 inhabitants, 1990

Proneness to disaster also depends on many other factors, including: physical characteristics of the city's location; differences in the material fabric of buildings and infrastructure; variable flows of resources and wastes that shape the urban metabolism; and degrees of coordination among different social agents charged with responsibilities for protecting city residents - especially the state. The surplus of resources that is available for investment in improvements to the urban fabric and the socio-economic status of the population are further important determinants of mega-city vulnerability. Such factors vary considerably from country to country but tend to favour reduced vulnerability in the cities of industrialized states. Elsewhere, as in Mexico City, they do the opposite.

Mexico City in its regional setting

Mexico City is the dominant city of Mexico, where it stands at the head of a growing number of large urban centres (fig. 9.1). The Federal District comprises the heart of Mexico City and the two terms are often used interchangeably.1 However, the mega-city has spread well beyond the District into the surrounding Basin (Valley) of Mexico. Many parts of the Mexico City Metropolitan Zone (MCMZ) or Central Region are now included within greater Mexico City. That Zone - which is the focus of this chapter - includes portions of six Mexican states: the Federal District, Hidalgo, Mexico, Morelos, Puebla, and Tlaxcala.

1 The name "City of Mexico," in the strict sense, refers exclusively to the old colonial city, which today forms the commercial centre of the metropolis.

Table 9.1 Population of the megalopolis of Mexico, 1970-1990

State

1970

% national

1980

% national

1990

% national

Federal District

6,874,165

13.56

8,024,498

12.00

8,235,744

10.14

Hidalgo

259,624

0.51

357,461

0.53

479,740

0.59

Mexico

3,285,288

6.48

6,044,871

9.04

8,973,925

11.05

Morelos

382,052

0.75

616,600

0.92

814,337

1.00

Puebla

896,286

1.77

1,342,305

2.01

1,689,789

2.07

Tlaxcala

319,850

0.63

456,729

0.68

629,885

0.78

Total Central Region

12,017,265

23.70

16,842,464

25.20

20,823,420

25.63

National total

50,695,000

100.00

66,847,464

100.00

81,249,645

100.00

Sources: Population and Housing Census, INEGI, Mexico, 1970, 1980, 1990, tables I, IX, X, and XI.

Mexico City has become a paradigm of fast and anarchic urban growth during the second half of the twentieth century (Ezcurra and Mazari-Hiriart, 1996). Between 1950 and 1975 its population expanded from 3 million to 11.9 million, while it advanced from fourteenth (1950) to third (1975) in the ranks of large cities. Today, with at least 18.5 million inhabitants - and perhaps as many as 20.8 million - Mexico City is among the world's three largest metropolitan areas (table 9.1). Similar meteoric urban growth has occurred in other developing countries, whereas the big cities of developed countries now generally have stable or declining populations. In 1950, 9 of the 30 largest cities were located in developing countries; by 1990 the balance had shifted - 17 of the top 30 cities belonged to developing countries.

According to some population projections, Mexico City will be the world's biggest urban place by the year 2000, with around 28.4 million residents. Whether these figures are correct is much disputed; recent United Nations estimates suggest that there may be as few as 15.6 million residents at the turn of the century. Compared with secondary cities such as Monterrey, the capital's "costs of admission" (i.e. for land, housing, employment, etc.) have risen prohibitively for poor in-migrants and may drive out some of those who are already there (Linden, 1996, p. 54).2

2 Other metropolitan zones such as Guadalajara and Monterrey are also growing fast (5.6 per cent and 5.83 per cent during 1960 - 1970, and 1980 populations of 2.3 and 2.0 million, respectively). Despite this, Mexico City still maintains its unquestionable primacy.

Mexico City clearly illustrates a distinctive feature of third world urbanization that has emerged in the years since the Second World War, namely the upsetting of more or less stable and complementary relations between city and countryside. On a worldwide basis this is reflected in the growing contribution of urban areas to gross domestic products and by the high concentration of development in a small number of large urban places. It is this process that has most challenged the state's capacity to respond to demands for urban investment and urban services. In 40 years Mexico City grew from 1,640,314 inhabitants (1940) to 13,354,371 (1980). During much of this period, annual growth rates varied between 5 per cent and 6 per cent, falling to around 4.4 per cent only in recent years, while the urbanized area increased from 117 km2 to 1,000 km2 (Ibarra, Puente, and Saavedra, 1988).

The rapidity with which mega-cities in developing countries are growing is particularly important for students of urban hazards. The big cities of the developed world (e.g. New York and London) took a long time to reach their present size - sometimes several centuries. Because the same process is occurring quickly in developing countries, the state's capacity to provide the necessary urban infrastructure is often exceeded. Prolonged conditions of scarcity, acute polarization, and social marginalization have become distinctive features of third world urbanization. In Latin America, the large urban agglomerations are what Bryant Roberts has labelled "cities of peasants," disproportionately made up of recent in- migrants from the countryside (Roberts, 1980). In Mexico City it has been difficult for migrants to adopt urban ways of behaving that involve cooperation, concentration, and subordination of the individual interest to the public interest. As a result, the effectiveness of existing public strategies for reducing urban vulnerability in the face of natural or social induced disasters is limited.

Socio-demographic profile

Expansion of urban territory

One important indicator of urbanization in Mexico City is the rate at which rural land is converted to urban uses. Before 1960, urbanized land was confined within the boundaries of the Federal District. Rates of incorporating new territory reached maxima during the 1920s (6.38 per cent per annum) and again during the 1940s (6.94 per cent). These growth spurts were triggered by broad changes in Mexican society. The 1920s were a time of recuperation after a decade of deep social conflict and urban paralysis during the Mexican Revolution. The 1940s witnessed an upsurge of industrialization that took advantage of a surplus of cheap and mobile labour. Population densities in the Federal District remained more or less constant throughout these decades. During the 1960s, municipalities of the State of Mexico added 22.1 per cent more people and 6.62 per cent more land. In the following decade, the increments were 10.29 per cent and 9.65 per cent, respectively. During the 1980s, however, population and territorial growth rates fell off and density declined; a period of reduced growth and spatial dispersion had begun (table 9.2).

The emergence of a dual city

Mexico City contains a mixture of dispersed and concentrated populations. The mega-city as a whole has been growing, but there have also been substantial shifts in the locus of population, and the State of Mexico is now growing fastest of all units of the Mexico City Metropolitan Zone (MCMZ). In 1970, the Federal District was twice as populous (6.9 million) as the State of Mexico (3.3 million), and the whole mega-city was home to a total of 12 million people. By 1990, the State of Mexico had almost tripled its population (8.9 million) and had overtaken the Federal District (8.2 million). At that time the Metropolitan Zone housed 20.8 million (later corrected to 21.6 million) (table 9.1).

During the 10 years between 1980 and 1990, although the natural population increase was substantial in the Federal District, almost as many people migrated out of the District to other parts of the mega-city (table 9.3). It is now clear that a dual city is emerging: a core, comprising the Federal District, and a periphery made up of the remaining parts of the mega-city. For the most part the core is socially heterogeneous but relatively stable, economically healthy (many residents receive medium to high incomes), and characterized by service employment. The periphery, situated predominantly in the State of Mexico, is occupied by people who have recently migrated there, receive incomes in the low to medium range, and are employed in secondary and tertiary economic activities including the informal economy.

Economic structure

Mexico City is the nation's premier economic centre. Its recent growth is largely the product of a post-war economic system that attempted to develop domestic resources and substitute them for imported goods. A by-product of this system was the concentration of people and production in a few urban centres - especially Mexico City - leaving much of the rest of the country underdeveloped. Now the negative consequences of the system, including excessive concentration, are becoming apparent.

Table 9.2 Rate of growth of urbanization, 1900-1990


Federal District

Conurbated municipalities

ZMVMa

Year

Urb. pop.(%)

Urb. area (%)

Density (inh./ha)

Urb. pop. (%)

Urb. area (%)

Density (inh./ha)

Urb. pop.(%)

Urb. area (%)

Density (inh./ha)

1900-1910

2.02

3.90

105.82




2.02

3.90

105.82

1910-1920

3.87

1.54

132.71




3.87

1.54

132.71

1920-1930

5.48

6.38

121.85




5.48

6.38

121.85

1930-1940

4.60

3.16

139.99




4.60

3.16

139.99

1940-1950

6.56

6.94

135.05




6.66

7.43

130.33

1950-1960

5.13

4.82

139.16



25.37

5.55

6.94

114.32

1960-1970

3.60

2.86

149.54

22.10

6.62

96.42

5.52

3.79

134.94

1970-1980

0.96

2.51

128.39

10.29

9.65

104.28

3.61

5.03

117.80

1980-1990

0.26

1.33

115.45

2.92

4.78

87.15

1.86

2.97

90.00

Source: Urban Plan of Central Region of the Megalopolis of Mexico, States of Mexico and the Metropolitan Autonomous University, 1993.

a. Metropolitan Zone of the Valley of Mexico.

Table 9.3 Population growth of the Central Region of the megalopolis of Mexico, 1980-1990

State

Total growth

Natural growth

Migration growth

Fed. District

211,246

1,723,585

-1,512,339

Hidalgo

122,279

115,115

7,164

Mexico

2,929,054

1,509,389

1,419,665

Morelos

197,737

193,892

3,845

Puebla

347,484

422,977

-75,493

Tlaxcala

173,156

162,992

10,164

Total

3,980,956

4,127,950

-146,994

Sources: Urban Plan of Central Region of the Megalopolis of Mexico, States of Mexico and the Metropolitan Autonomous University, 1993.

The dynamics of economic growth

Prior to the Second World War, industrialization in Mexico was very limited and was largely restricted to mining and textiles. But after 1940 industrialization took off in step with urbanization. Industries gravitated especially towards Mexico City, attracted by its long-established political and economic importance and its steady economic growth. In 1940, Mexico City accounted for 30.6 per cent of the national gross domestic product (GDP). It dominated some economic sectors more than others (e.g. transportation - 66.6 per cent; industry - 33.7 per cent) (table 9.4). During the next four decades (1940 - 1980), the MCMZ's share of GDP increased slowly, peaking in 1980 at 38.2 per cent. Over this period, the (standardized) value of the MCMZ's contribution increased from 7 billion pesos in 1940 to 115 billion pesos in 1980 - a sixteenfold increase. Not surprisingly, the city underwent profound social and economic changes.

Trends in different economic sectors showed considerable fluctuations and dramatic contrasts during these 40 years. For example, the MCMZ's share of the national industrial sector rose from 34 per cent (1940) to 43 per cent (1960) and then fell back to 31 per cent (1980). Conversely, the service sector grew continuously, from 41 per cent (1940) to 51 per cent (1980). Finally, the MCMZ transportation sector's share of GDP was cut in half from 67 per cent (1940) to 34 per cent (1980). Data about the changing sectoral shares of the MCMZ's own GDP show that services have generally been most important overall and account for an increasing proportion of the total, whereas industry declined slightly during the period 1940 - 1980 (Puente, 1987). Reductions in the share of GDP accounted for by industry - in both the country as a whole and the MCMZ - must be viewed against real absolute increases in production, which continued throughout the period of record. A declining share of industrial GDP merely indicates that industrial investments were not confined solely to Mexico City; other urban centres also became industrialized.

Table 9.4 National and Mexico City's gross national product, by economic sector, 1940-1980 (millions of 1950 pesos)


1940

1950

1960

1970

1980

Rate of growth, 1970-1980


National

MCMZ

National

MCMZ

National

MCMZ

National

MCMZ

National

MCMZ

National

MCMZ

Total

22,889

7,010

41,060

12,427

74,215

26,858

151,760

56,731

301,731

115,338

2.0

2.0

Agriculture

5,170

30

9,242

28

13,917

37

17,643

54

25,198

105

1.4

1.9

Industry

6,789

2,286

12,466

3,378

24,603

10,509

52,009

16,086

112,509

34,619

2.1

2.2

Transport

865

576

1,988

1,038

3,638

2,184

4,778

2,775

13,903

4,788

2.9

1.7

Services

10,065

4,118

17,364

7,983

32,057

14,128

77,330

37,816

150,121

75,826

1.9

2.0

MCMZ as % of national

Total

100.0

30.6

100.0

30.3

100.0

36.2

100.0

37.4

100.0

38.2



Agriculture

100.0

0.6

100.0

0.3

100.0

0.3

100.0

0.3

100.0

0.4



Industry

100.0

33.7

100.0

27.1

100.0

42.7

100.0

30.9

100.0

30.8



Transport

100.0

66.6

100.0

62.2

100.0

60.0

100.0

58.1

100.0

34.4



Services

100.0

40.9

100.0

46.0

100.0

44.0

100.0

49.0

100.0

50.5



Economic sector as % of total

Total

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0



Agriculture

22.6

0.4

22.5

0.2

18.7

0.1

11.6

0.1

8.4

0.1



Industry

29.6

32.6

30.4

27.2

33.2

39.1

34.3

28.4

37.3

30.0



Transport

3.8

8.2

4.8

8.4

4.9

8.1

3.1

4.9

4.6

4.2



Services

44.0

58.8

42.3

64.2

43.2

52.7

51.0

66.6

49.8

65.7



Sources: Mexican National Account System, Gross National Product by Federal States, General Direction of Statistics, SPP, 1982.

Although the MCMZ's share of national GDP decreased, absolute numbers of establishments (firms) rose from 27,707 (1960) to 33,049 (1970) and then to 34,549 (1975). Yet assets (capital invested) and numbers of personnel both began to decline by the mid-1970s. What appears to have occurred in Mexico City during the decades between 1940 and 1980 is a proliferation of small-scale establishments using low-paid labour. More industrial establishments were created in the MCMZ, but total assets there declined as investments were relocated to other parts of Mexico. The figures point to a complex transformation of the country's industrial structure. Larger numbers of business enterprises became concentrated in the MCMZ but value-added did not grow proportionately, and investments began to be dispersed more widely throughout Mexico.

Data provided by the most recent economic censuses and estimates made by the National Institute for Geography and Statistics (INEGI) indicate no significant changes in the Mexico City Metropolitan Zone's share of the national GDP for 1985 and 1988. This remains between 37 per cent and 38 per cent. Unfortunately, apart from the Federal District and the State of Mexico, the rest of the mega-city is attracting much less new investment. For residents of the Valley of Mexico, the benefits of shifting (diversifying and deconcentrating) investment towards cities in Puebla, Tlaxcala, Hidalgo, and Morelos (i.e. beyond the Valley of Mexico) would be manifold: (1) industrial and vehicular pollution in the central cities would be reduced; (2) the conversion of highly productive agricultural land and biologically rich ecosystems on the fringes of the present built-up area would be slowed; and (3) there would be a reduction in levels of the catastrophe potential of natural disasters. Mexico City's powerful attraction for economic investment has defeated all policies of deconcentration and dispersal up till now. Some experts view the North American Free Trade Agreement as a structural factor that will make a profound difference by shifting industrial plants from Mexico City to communities on the frontier with the United States.

Environmental hazards and urban vulnerability

Mexico as a whole is affected by a wide range of natural hazards. Geological hazards, particularly earthquakes, subsidence, and volcanoes, are of particular importance, but hydrological risks (e.g. floods and drought) are also significant. Moreover, the city is also at risk from serious air and water pollution and from an increasing number of technological emergencies such as natural gas tank explosions. The potential for social hazards is believed to be increasing, although accurate statistics are not available to substantiate this judgement.

Seismic hazards

Crossed and encircled by numerous geological faults and straddling several tectonic plates, the Mexican Republic is one of the world's most seismically active countries. Five important plates meet in the vicinity of Mexico: Cocos, Pacific, North American, Caribbean, and Rivera. Two seismic phenomena are particularly important: (1) lateral slipping, which takes place at the boundary of the Pacific and North American plates, and (2) subduction of the Cocos plate beneath the North American plate. Both of these phenomena are permanent generators of earthquakes, which have affected Mexico throughout its history. Major continental faults such as the San Andreas cross the entire country, while regional and local faults fracture much of the intervening territory. Of particular importance is the Acambay system of faults near the centre of Mexico and the Ocosingo system of Chipias State in southern Mexico (Sistema Nacional de Proteccion Civil, 1991).

Situated in the centre of the country, Mexico City is affected by many faults that cut across areas of greatest population density such as the historic centre. By themselves, the faults render the city potentially vulnerable to seismic movements, including sudden subsidence. In addition, the city is constructed on what was, until the turn of the century, a system of lakes that covered much of the Valley of Mexico. In other words, Mexico city is founded on saturated mud and clay soils that are particularly unstable. Among other things these soils amplify seismic waves up to 30 times more than do the firmer soils of adjacent higher zones. Movements in the tectonic plates offshore from Michoacan and Guerrero States pose the most serious threat to Mexico City. During the twentieth century, 34 tremors of Richter magnitude 7.0 or greater have occurred, almost all of them centred in this zone. Seismic activity is also manifest in the continental plates, particularly in association with the volcanoes that surround Mexico City. For example, Popocatepetl, whose last major eruption took place in 1920, became active again in December 1995, and Xitle or Teuhtli are also possible earthquake generators (Kovach, 1995, pp. 170 - 171). Although of low intensity and rarely damaging, these tremors alarm local populations; they are of little importance compared with those of the offshore Pacific plate. On occasions they have reached magnitudes of 7.0 (e.g. Acambay, State of Mexico, 1912).

Mexico's proneness to seismic activity is clearly reflected in a succession of twentieth-century earthquake disasters (table 9.5). All but one had intensities of 7.0 or greater. Several significantly affected Mexico City. In 1912, a magnitude 7.0 earthquake centred in the State of Mexico produced numerous landslides and killed 202 people. In 1932, a magnitude 8.4 event induced strong motion in Mexico City but did little damage. In 1957, a magnitude 7.7 quake, centred on the coast of Guerrero, killed 98 and caused the collapse of buildings in the capital. It also brought about various improvements in earthquake engineering practice (Esteva, 1997). Most recently, there occurred an even more destructive event.

Societal impact of the 1985 earthquake on Mexico City

On 19 - 20 September 1985, a series of earthquakes - including one of Richter magnitude 8.1 - killed at least 3,050 people, injured 40,750, rendered 80,000 homeless, destroyed 1,970 buildings and damaged 5,700 more. Total material losses were estimated at 1,000 billion pesos (Sistema Nacional de Proteccion Civil, 1991). These are official loss figures and they may understate the death toll. A different authoritative source lists around 4,500 dead but only 14,000 injured (Atlas de la Ciudad de Mexico, 1987). Others have accepted much higher estimates (Cevallos, 1995), perhaps as many as 5,000 - 10,000 dead.

Data on building losses are even more varied. Rivas Vidal and Salinas Amezcua list only 412 buildings totally destroyed, but agree with other sources about the number of buildings that were damaged (5,728). Many damaged buildings eventually had to be demolished; others that ought to have been pulled down for structural safety reasons were repaired at the insistence of their inhabitants. Among the latter was the Nonalco-Tlatelolco housing estate, which comprised 102 separate buildings. When constructed in the early 1960s the estate was intended to be a model of state responses to joint needs for slum clearance, new housing, and improved architectural design. It is significant that this estate was one of the most badly affected by the quake. Critics have speculated that poor-quality construction as a result of corrupt government practices may have been responsible for the dcle. That explanation takes on added significance in light of other failures of government-sponsored projects. For example, Mexico City lost 30 per cent (3,457 beds) of its installed hospital capacity, all belonging to government social security institutions; most of these were in buildings constructed after 1950. The destruction of the Centro Medico was a particularly egregious loss. Infrastructure damage was heavy, although some systems (e.g. underground rail transport) were unaffected. The city's telephone service was crippled by the quake and contacts with the outside world were severed. It took approximately six weeks before the bulk of telephone communications were reinstated. Drinking water supplies and drainage networks were also disrupted for long periods. Fractured supply pipes leaked water and 17 major junctions of the drainage system were damaged. Water supplies were not fully restored for a month and a half. Even today it is still possible to find evidence that the aftermath has not ended.

Table 9.5 Main catastrophic earthquakes during the twentieth century

Date

Region

Affected population

Magnitude (Richter scale)

Damage

19 Nov. 1912

State of Mexico

Acambay, Timilpan, and Federal District

7.0

Landslides; 202 deaths and several injuries

4 Jan. 1920

Puebla, Veracruz

Cosautlan, Teocelo, and Jalapa in Veracruz; Patlanala and Chilchotla in Puebla

6.5

Landslides; 230 deaths and several injuries

3 June, 1932

Jalisco, Colima

Manzanillo, Coyutla, Tecoman, and Colima in Colima; Guadalajara, La Barca, Mascota, and Autlan in Jalisco

8.4

300 deaths and several injuries

26 Jul. 1937

Oaxaca, Veracruz

Maltrata in Veracruz

7.3

34 deaths

15 Apr. 1941

Michoacan, Jalisco

States of Michoacan, Jalisco, and Colima

7.9

Destruction of Colima City's Cathedral; 900 deaths and several injuries

28 Jul. 1957

Guerrero

San Marcos and Chilpancingo in Guerrero, and Federal District

7.7

Collapse of several houses and buildings; 98 deaths; and tsunami in Acapulco and Salina Cruz

6 Jul. 1934

Guerrero, Michoacan

Cd. Altamirano, Cutzamala, and Coyuca de Catalan in Guerrero; Tanganhuato and Huetamo in Michoacan

7.2

40 deaths, 140 people injured; heavy material losses

29 Aug. 1973

Oaxaca, Veracruz

Puebla, Veracruz, and Oaxaca

7.3

Collapse of houses and severe damage to buildings; 527 deaths and 4,075 people injured; high material losses

24 Oct. 1980

Oaxaca, Puebla

States of Oaxaca, Guerrero, and Puebla

7.0

300 deaths, 1,000 people injured, 15,000 homeless

19 Sep. 1985

Michoacan, Guerrero

Michoacan, Colima, Guerrero, Mexico, Jalisco, Morelos, and Federal District

8.1

3,050 deaths, 40,750 people injured, 80,000 homeless; 1,970 buildings collapsed and 5,700 buildings badly damaged; heavy material losses

Source: National Autonomous University of Mexico, Institute of Geophysics.

It is sometimes argued that the population of Mexico has historically accepted natural calamities as a part of normal life. Many individuals have exhibited traits of passivity, acceptance, resignation, or stoicism in the face of hazard. Though victims were undoubtedly grieviously distressed and the frequency of such misfortunes was high, the effects were usually limited. This situation changed radically after 20 September 1985. Not only was the earthquake's magnitude unprecedented in Mexico City, it shook local society to such an extent that manifold everyday problems of marginalization, poverty, unemployment, anarchy, and pollution were eclipsed for a considerable period. Both government and civil society were surprised by the results.

Fearful of any situation that might upset the fragile social stability that existed in Mexico City despite acute social polarization, government leaders at first tried to play down the event and proclaimed their own ability to deal with the resulting problems. International offers of aid were initially spurned. But the slowness of rescue operations and the lack of timely information from the government induced residents to take matters into their own hands. In the absence of effective state-sponsored relief, the efforts of informal public groups and individuals were highly valued. Despite a lack of coordination and experience, much was achieved, including the rescue of at least 3,226 people. In addition, the success of public involvement demonstrated the existence of a formerly untapped but vast potential for social initiative, participation, and solidarity among ordinary citizens. This realization was not lost on the government, but it triggered fears that protests might subsequently occur and undermine political stability. As a result, a call was issued for residents to return to normal activities while the government reasserted its authority and control. None the less, it was recognized that informal public action had successfully produced housing and other resources for destitute residents (Connolly, 1993); so the state began to capitalize on the people's initiative, institutionalizing it as a formal government programme. Now the state would provide financial and technical assistance but the people were required to organize themselves and contribute their own labour to carry out requested urban improvement works. In effect this was a belated official recognition of private - and illegal - practices that had long existed in Mexico City, whereby land and buildings are often appropriated by poor squatters and housing is constructed or converted by informal community groups. Whether this type of response has come in time to offset the degeneration of urban life in Mexico City remains to be seen. However, it earned the government much political capital over the following two years, out of which was created the Ministry of Social Development (SEDESOL), previously the Ministry of Ecology and Urban Development (SEDUE).

It is estimated that sufficient elastic energy has built up in the Guerrero section of the Pacific plate boundary that another earthquake of similar magnitude to that of 1985 could occur there soon, with devastating consequences for Mexico City. It is also known that the most seismically vulnerable parts of the capital are located in central residential neighbourhoods such as Cuauhtc, Venustiano Carranza, Gustavo A. Madero, and Benito Juz, which are founded on unstable lacustrine soils. The urgency of implementing preventive measures is obvious. Towards that end it is essential to carry out detailed seismic risk mapping that also takes account of Mexico City's socio-economic heterogeneity. In addition to being useful tools for increasing public awareness of risk, such maps facilitate the setting of priorities for action.

Lack of sensitivity to the social dimensions of earthquakes is reflected in many public safety programmes throughout Mexico City. One example is the earthquake warning system, which relies on distant ground motion sensors and rapid transmission of radio and television signals to targeted vulnerable facilities. Using this system it is possible to provide residents of Mexico City with at least a 1 minute warning of earthquakes occurring in Michoacan and Guerrero states or adjacent offshore waters. That may be sufficient for individuals in homes and small businesses to take protective action, but it is questionable that people in large, densely occupied facilities such as stadiums, major stores, and factories could be evacuated; many might be injured in rushing for exits. The system was suspended shortly after being introduced because of technical malfunctions that triggered delayed or bogus warnings. Since then improvements have been made and several schools have conducted tests that produced hopeful results. However, without broader public education and training the prospects for success of this warning system are still in doubt. Myopia about social factors in disasters begins at the top of disaster agencies in Mexico, including those, such as the National System of Civil Defence, that were established right after the 1985 earthquake. Failure to take account of the composition of populations at risk compromises public policies and hampers the introduction of sophisticated technologies for the prevention of natural risks.

Other environmental hazards of Mexico City

Floods, water shortages, and associated famines have been an important feature of Mexico City's history and at least the first two of these are continuing hazards. The closed, internally drained basin of Mexico is particularly susceptible to disruption of its hydrological system, and human modifications of local ecosystems have been extensive. The floods of 1629 - which submerged the capital for five years - may have killed as many as 30,000, and further severe inundations occurred in 1691. Major drainage works were completed in the late seventeenth century that sufficed for over a hundred years, but additional heavy investment in canals, pumps, and tunnels was required at the end of the nineteenth century (Kandell, 1988, pp. 371 - 372). Even then, flooding continued as a sporadic troubling hazard (e.g. in 1910).

Environmental pollution has become a grave endemic problem in Mexico City. Almost every day, the permissible limits of atmospheric pollution are exceeded. Elevated levels of tropospheric ozone cause most problems. It is estimated that total pollutant emissions by weight are approximately 5 million metric tons within the Mexico City Metropolitan Zone: 15 per cent from fixed sources (e.g. buildings), 80 per cent from mobile sources (i.e. vehicles), and the rest (5 per cent) from natural sources (Sistema Nacional de Proteccion Civil, 1991). The enclosed basin in which Mexico City sits ensures that locally generated air pollutants are not subject to much dispersal, especially during winter when thermal temperature inversions are common (New York Times, 4 February 1996). Anti-pollution programmes have not had any significant effect in reducing these problems, though not for the want of trying. The lead content of petroleum has been considerably reduced, but ozone levels have risen. The Azcapotzalco refinery, which was a primary source of hydrocarbon emissions, has been closed down. An obligatory annual anti-pollution test of road vehicles was introduced and then applied every six months. The "Hoy no circula" programme, which prohibits the use of each vehicle on one day a week, has also been adopted. But beneficial results have been minimal and some measures have produced perverse effects. The "day without driving" programme has largely become a "day off work." Among middle-class residents it has also prompted the purchase of additional cars that can be driven when primary vehicles are barred from use. In addition, the enforcement of pollution controls against highly polluting industries has been extremely lax. Chemical and cement plants have resisted installing anti-pollution equipment, preferring to invest in bribes to enforcement officials.

Nor is the problem solely one of poorly conceived public policy. The diagnosis of pollution causes is inadequate and the means to control pollution are still insufficient. For example, it is difficult to explain why levels of pollution remain high at weekends; this is a time when most industries stop production, a majority of the population rests, and large numbers of residents are absent from the city. It is probable that the contributions of various individual and family behaviours to pollution have been underestimated. These might include cooking with bottled gas and widespread private burning of rubbish.

Fires and explosions constitute other important socially induced technological disasters. Between 1982 and 1984, there was an average per year of about 20,000 fires and explosions throughout Mexico, of which 3,474 took place in the Federal District and 925 in the State of Mexico. Nearly 500 people died throughout the country from these causes, including approximately 100 in the State of Mexico, where there are many industries, urban deprivation is high, and incomes are low (table 9.6). Most of the fires are of domestic origin (68 per cent), ahead of fires in commercial premises (20 per cent), with industrial fires making up the rest (12 per cent). In the Federal District, the frequency of fires varies widely from neighbourhood to neighbourhood. The highly populated and densely industrialized central delegaciones of Cuauhtc, Madero, and Hidalgo are particularly fire prone (table 9.7). In contrast, the pre dominantly agricultural, low-density, peripheral delegaciones of Tlac, Milpa Alta, and Xochimilco experience fewer than 5 per cent of all fires despite the fact that these are places where slash-and-burn cultivation is practised and both the burning of rubbish and the ignition of celebratory bonfires are common. As urban development spreads into these areas, the possibility is growing that loosely supervised rural fires might spread to built-up areas, especially during the dry months of February, March, and April.

Catastrophic industrial explosions have occurred in Mexico City and are a continuing threat. For example, on 19 November 1984, 334 people were killed when a natural gas storage facility exploded in the north-eastern neighbourhood of San Juanico. Perhaps more indicative of the complex nature of urban industrial hazards is the example of Guadalajara's sewer system explosion in 1992. This was fuelled by leakage of gasoline from a refinery owned by the national petroleum company of Mexico (Pemex). An extensive residential zone blew up, causing widespread damage and loss of lives. The negligence of the local authorities was patently obvious. Days before, inhabitants of the affected neighbourhood had reported the leak, but the municipal authorities had not responded. Other contributory factors included lax and unobserved public safety regulations, lack of maintenance and obsolescence of the sewer system, and absence of coherent urban planning. These are the kinds of problem that are all too common in Mexico's large urban centres, especially Mexico City, and which make living there an experience of chaos that is permanently on the verge of catastrophe.

In short, Mexico City is a place of contradictions. Far from being a city that has solved problems of environmental risk and hazard, it has become the setting where a multitude of such problems converge (Puente, 1988). In order to address the hazards it is important to understand the dominant social actors who produce the city that generates them. These are individuals and institutions that affect the city's quality of life as well as its vulnerability to natural and socially induced risks.

Table 9.6 National urban fires and explosions, by federal state, 1982-1984 (annual means)

Federal state

No. of fires and explosions (annual mean)

Domestic

Commercial

Industrial

No. of people killed

Aguascalientes

173

111

48

14

2

Baja California

1,539

1,023

318

198

19

Baja California Sur

171

129

35

7

1

Campeche

70

39

18

13

-

Coahuila

1,082

736

256

90

8

Colima

134

106

21

7

2

Chiapas

36

20

12

4

1

Chihuahua

1,845

1,317

376

152

21

Distrito Federal

3,474

2,471

635

368

15

Durango

252

194

31

27

7

Guanajuato

1,103

824

130

149

28

Guerrero

167

97

63

7

1

Hidalgo

217

134

73

10

93

Jalisco

520

313

142

65

6

Mco

925

510

195

220

104

MichoacBR>

483

370

89

24

7

Morelos

212

131

59

22

7

Nayarit

163

124

28

11

8

Nuevo LeR>

1,635

911

331

393

15

Oaxaca

184

158

24

2

6

Puebla

367

208

95

64

13

Querro

288

186

78

24

7

Quintana Roo

213

137

27

49

-

San Luis PotosR>

369

264

79

26

4

Sinaloa

575

327

191

57

13

Sonora

1,787

1,212

367

208

62

Tabasco

206

123

67

16

3

Tamaulipas

971

738

188

45

10

Tlaxcala

-

-

-

-

-

Veracruz

620

445

139

36

21

YucatBR>

205

144

4.4

17

-

Zacatecas

40

33

4

3

-

Total

20,026

13,535

4,163

2,328

484

Source: Secretary of Budget and Planning, National Institute of Statistics, Geography and Information.

Table 9.7 Fires in Mexico City (Federal District), by delegacion, 1974, 1979,1984

Delegacion

1974

1979

1984

Mean

%

Gustavo A. Madero

212

311

263

262

11

Venustiano Carranza

182

266

225

224

9

Cuauhtc

424

621

525

523

21

Iztacalco

99

146

123

116

5

Benito Juz

166

243

205

205

8

Iztapalapa

133

194

164

164

7

CoyoacBR>

110

160

136

135

6

Tlac

48

70

59

52

2

Milpa Alta

5

8

7

7

0

Xochimilco

35

51

43

43

2

Tlalpan

100

146

124

123

5

Magdalena Contreras

22

33

28

28

1

Alvaro ObregR>

147

215

182

181

7

Cuajimalpa

12

17

14

14

0

Miguel Hidalgo

209

306

258

258

11

Azcapotzalco

99

145

123

122

6

Total

2,003

2,932

2,479

2,457

100

Source: Based on Department of Protection and Transport, September 1984.

Assessing the vulnerability of Mexico City

Mega-cities of developing countries are vulnerable to environmental hazards for a complex mixture of reasons (Eibenschutz and Puente, 1991). But the crux of the problem is an inability to cope with very rapid population growth and extreme socio-economic polarization between rich and poor neighbourhoods. In Mexico City, inner neighbourhoods are compact, multistoreyed, well served and well equipped, and oriented towards consumption. Outer neighbourhoods are sprawling low-rise places, deficient in housing, infrastructure, and services, and oriented to production. Much of the outer city is occupied illegally by squatters; settlements spread indiscriminately over land of high agricultural productivity and low seismic resistance. It is probable the occupants of these informal settlements are also undergoing profound social transformations, but little is known about the urban acculturation of the new arrivals. However, it is clear that the informally settled areas are disproportionately poorly serviced and vulnerable to disaster.

A spatially distinctive hierarchy of vulnerabilities

In principle, cities are vulnerable to disasters in four distinct but interacting ways. First, they are internally vulnerable because of weaknesses of social and material infrastructures (e.g. people who lack the resources to improve protection against disaster; centralized utility networks without adequate backup systems). Secondly, cities are more vulnerable if they are dependent on rural hinterlands that are themselves vulnerable (e.g. in-migrant refugees from rural famines and civil wars impose heavy burdens). Thirdly, cities that are lower in the national urban hierarchy may be more vulnerable than those near the top of the system because their claims on public and private resources are less effective. Fourthly, and for similar reasons, cities that lie at the centre of the global economic system (e.g. the polycentre) are less vulnerable than those on the periphery. Tokyo and Los Angeles are less vulnerable than Calcutta and Mexico City. For a given city, one type of vulnerability may be of overwhelming importance or there may be several lesser vulnerabilities acting together synergistically. Increasing interdependence among different levels of the global urban system is likely to confer benefits on the entire system by reducing the dependence of any single city - though whether this might lead to the build-up of a potentially catastrophic system-wide failure is not clear. How shall the multiple vulnerabilities of mega-cities be identified and assessed? The next section takes up this question.

Factors and gradients of vulnerability: A matrix approach

The following methodology for assessing urban vulnerability rests on two premises: (1) the material conditions of a city are good indicators of vulnerability; (2) the main components of vulnerability can be mapped at the scale of urban neighbourhoods. It only remains to create a matrix that displays the appropriate indicators (factors) on one axis and the areal units of analysis on the other. For the purposes of this chapter, five clusters of vulnerability factors are included. These are:

• natural factors (e.g. geomorphic, climatic, biotic, edaphic)

• material factors (e.g. infrastructure services, equipment, housing, economic base, spatial organization)

• environmental factors (e.g. pollution levels, biotic variety, amenity lands)

• socio-economic factors (e.g. household composition, mortality, life expectancy, morbidity, occupation, income, nutrition, social organization)

• psychological factors (e.g. perception of environment, tension, anxiety)

Natural factors

The contribution of natural factors towards urban vulnerability varies widely from city to city. In Mexico City, seismic factors and landforms are especially important. Many of the landforms have been subject to extensive human manipulation. For example, along the shores of the original lakes that dotted the valley floor, artificial floating "garden" platforms (chinampas) once provided food for local residents. Today, these water bodies have been drained and desiccated, the hydrological cycle has been altered, forest cover has been reduced from 54 per cent to 14 per cent, and the floating agricultural lands have been taken over by urban uses. The seismic vulnerability of dried-out lake beds is particularly high, but the city's soils vary in complex ways and there is a trend toward greater vulnerability almost everywhere.

Material factors

Deficiencies in the material fabric of mega-cities contribute to disaster-vulnerability. Buildings and infrastructure are strongly affected by prevailing technologies. Some technologies can be transferred successfully between countries but others are less versatile. When a technology that has been specifically developed for one country - or one city - is transferred to another, perverse effects may be generated. These include: inappropriate fit with local ecosystems and environments; high costs of construction and operation; breakdowns, deterioration, and obsolescence; and the unanticipated consequences of replacing existing traditional technologies that depend on human labour with technologies that are predominantly non-human. Poor-quality urban technologies are a widespread problem in developing countries. Inadequate construction and maintenance can render even the best-designed technology inoperable. The wastage of water in Mexico City because of leaks in supply pipes is well known. Up to 45 per cent of the initial supply is believed to be lost - a staggering proportion in view of the fact that much water must be brought to the city from remote sources outside the Valley of Mexico and many residents receive no formal water service.

Material contributions to vulnerability change in response to the process of urbanization. For example, growing cities often swallow up potentially hazardous industries that were originally outside the built-up zone. Once surrounded by housing, these sites face an increased probability of disaster. A sound urban policy can reduce such risks by channeling new development onto suitable land and by promoting a coherent spatial arrangement of residential and industrial uses.

Environmental factors

Environmental pollution is an increasingly serious problem in third world cities. In the pre-urban past, significant pollution was often non-existent or inconsequential. Later, when industrial development became viewed as a corollary of modernization, it was regarded as a price that society must pay to obtain higher incomes. It is just recently that some countries have recognized pollution as a public health problem to which cities are highly sensitive and vulnerable.

Pollution arises from both fixed and mobile sources. Industrial facilities in the mega-cities of developing countries have rarely been subject to policies of pollution control. Equally important is pollution generated by urban transportation systems, especially those that depend on motor vehicles. In recent years, local authorities have been obliged to put up with crawling traffic, many frequent traffic jams, and other forms of vehicular paralysis. The supposed advantages of flexibility and speed that were associated with motor vehicles are rapidly disappearing. None the less, these cities must live with the permanent costs of neighbourhood social disruption and increased pedestrian hazards that have followed in the wake of motorization. Similar problems of overuse and undermanagement have also affected water resources. Lack of treatment facilities has led to the contamination of streams where wastes are deposited and of the associated aquifers.

Socio-economic factors

Mega-cities of developing countries are typically characterized by spatial patterns of great social inequality. These patterns are affected by the decisions of three different groups: real estate agents and urban developers; the state; and the poor or informal sector. Today the last of these three is increasingly prevalent in the big cities of developing countries. The spatial differentiation of different social classes occurs in several stages (Puente, 1988). These stages are most noticeable for the informal sector because of the slowness with which the conditions of the poor change.

The vulnerability of a specific residential area in an informal settlement varies according to the stage of urbanization. Initially, the less the degree of development, the greater the vulnerability. At the outset, infrastructure is almost non-existent and is of very poor quality. Housing is equally poor and, as it is extended or upgraded, vulnerability may remain high because the technologies available to the users are unsophisticated and there is little compliance with building codes or other standards. These disadvantages may be offset by the improved access to information that comes with better education, thereby increasing the likelihood that residents will join in timely evacuations when threatened by disaster. This produces a paradox. Efforts to enlist the poor in government-sponsored self-help schemes that are intended to reduce vulnerability depend on generating a minimum level of social cohesion and interaction among the target groups. But self-reliant communities are often seen as threatening by the state and may attract government-inspired attempts to undermine or manipulate them.

Clearly, the reinforcement of local social organizations could be an excellent instrument to minimize vulnerability. Not only would such institutions be useful as vehicles for publicizing and facilitating anti-disaster measures, they would help to avoid conflicts about relocation of people from high-risk settlements. Today such measures are almost non-existent, notwithstanding the risks to which mega-cities - including Mexico City - are exposed. Of course, it must also be remembered that the participation and organization of the poor residents of informal settlements are not - by themselves - sufficient to reduce the disaster-vulnerability of third world mega-cities. There also must be a clear consensus about the goals of urban development. Otherwise, duplications and contradictions will be generated. The state has a leading responsibility to articulate and foster these goals, which until now it has barely assumed.

Psychological factors

Psychological factors that affect vulnerability are difficult to measure but none the less important. Such factors are the basis of individual and social anomie and pathological behaviour. They also affect potentials for increased social interaction, cohesion, and organization. Migrant populations are slow to adopt urban lifestyles in Mexico City. The migration process generates profound geographical and cultural imbalances that impair the satisfaction of basic human needs for empathy and identity. Uprooted from places of origin, faced with behaviour patterns different from their own, and surrounded by an indifferent and even hostile environment, newcomers have developed distinctive behaviours that may protect the psyche but do not necessarily reduce vulnerability to other hazards. Guided by primary instincts for survival, migrants react against their new surroundings, often by means of aggressive confrontations that not infrequently lead to criminal or anti-social conduct. Tension, anxiety, and aggression are psycho-social traits that undermine the achievement of identity, social well-being, and security. They counteract integration, cooperation, and social organization.

The preceding are some - but not necessarily all - of the factors that affect vulnerability in the city. Together they determine the spatial pattern of vulnerability, and occasionally one of them largely dominates it. By assigning a value to each factor it is possible to create a comprehensive index, which is here referred to as the Compound Index of Urban Vulnerability. This index is derived by dividing the sum of the (weighted) values for each factor by the number of factors. Separately, the relative importance of each factor can be shown for different areas of enumeration; positive scores (i.e. high vulnerability) for some factors might be offset by negative scores (i.e. low vulnerability) in others. For example, poor-quality housing might coexist with relatively high levels of education.

Application of the matrix to Mexico City

The purpose of this matrix is to identify Mexico City's most vulnerable areas, so that priorities for hazard reduction can be established. It has not yet been possible to find appropriate data for all matrix categories. Therefore the vulnerability indices that are derived here for Mexico City are preliminary and could be improved with better data and finer analytic procedures. Nevertheless, this instrument has great potential utility in the formulation of effective policies and decisions about urban hazard reduction. The measures of vulnerability that were included in the Mexico City Vulnerability Index were:

1. Socio-economic factors:

- Size and density of urban concentration
- Material conditions of housing
- Density and type of housing
- Level of education
- Employment (sectoral occupation of the population)
- Income level
- Economic activity (industrial density, especially of dangerous industries such as petroleum and chemicals).

2. Regional infrastructure:

- Electricity network and power stations
- Gas network
- Oil network
- Water supply network.

3. Urban spatial structure:

- Level and quality of the physical urban services: sewerage, electricity, and road and transport system.

4. Natural factors:

- Soft soils with high seismic amplification
- Seismic zones with high amplification
- Seismic zones with medium amplification
- Seismic zones with medium- to low-range amplification
- Landslides
- Mining zones
- Mudslide zones
- Flooding zones with medium and low seismic amplification.

For analytical purposes, the study area has been divided into two broad zones: (1) the Federal District; and (2) the metropolitan zone, which lies mainly within the federal state of Mexico. This division ignores and cuts across the activities that link both parts of the mega-city, but it recognizes the basic distinction between a fast-growing zone (State of Mexico) and a slow-growing one (Federal District). The spatial units of analysis used in the matrix are those employed in Mexican population censuses: delegaciones in Mexico City and municipios in the MCMZ (see fig. 9.2). They vary in size and economic composition: some are already highly urbanized, industrialized, and thoroughly integrated into the city; others have small scattered populations, and are quasi-rural but physically connected to the city.


Fig. 9.2. The delegaciones and municipios of the mega-city of Mexico

KEY:

Federal District delegaciones:

002

Azcapotzalco

003

CoyoacBR>

004

Cuajimalpa de Morelos

005

Gustavo A. Madero

006

Iztacalco

007

Iztapalapa

008

Magdalena Contreras, La

009

Milpa Alta

010

Alvaro ObregR>

011

Tlac

012

TIalpan

013

Xochimilco

014

Benito Juz

015

Cuauhtc

016

Miguel Hidalgo

017

Venustiano Carranza

State of Mexico municipios:

002

Acolman

009

Amecameca

010

Apaxco

011

Atenco

015

Atlautla

016

Axapusco

017

Ayapango

020

Coacalco

022

Cocotitlan

023

Coyotepec

024

Cuautitlan

025

Chalco

028

Chiautla

029

Chicoloapan

030

Chiconcuac

031

Chimalhuacan

033

Ecatepec

034

Ecatzingo

035

Huehuetoca

036

Hueypoxtla

037

Huixquilucan

038

Isidro Fabela

039

Ixtapaluca

044

Jaltenco

046

Jilotzingo

050

Juchitepec

053

Melchor Ocampo

057

Naucalpan de Juz

058

Netzahualcoytl

059

Nextlalpan

060

Nicolas Romero

061

Nopaltepec

065

Otumba

066

Otzoloapan

069

Papalotla

070

Paz, La

075

San Martin de las Piramides

081

Tecamac

083

Temamatla

084

Temascalapa

089

Tenango del Aire

091

Teoloyucan

092

Teotihuacan

093

Tepetlaoxtoc

094

Tepetlixpa

095

Tepotzotlan

096

Tequixquiac

099

Texcoco

100

Tezoyuca

103

TIalmanaIco

104

TIalnepantIa

108

Tultepec

109

Tultitlan

112

Villa del Carbon

113

Villa Guerrero

120

Zumpango

121

Cuautitlan-Izcalli

State of Hidalgo municipio:

069

Tizayuca

It is assumed that vulnerability is partly a function of population size, and this is built into the socio-economic component of the matrix by means of weighted values. There are three units of over 1 million people, but most possess fewer than 15,000 inhabitants. Building materials, housing types (detached, high-rise, etc.), and density form a second key component of vulnerability. Higher education is a third factor because it correlates with improved capacities for social interaction and the management of problems. Income levels are included because housing improvements are likely to be a function of economic surpluses, though recent data call this assumption into question (Puente, 1988). Occupation types and economic sector (transportation, industry, etc.) are included because they reflect the potential for human-made disasters - especially those involving the chemical and petroleum industries. Likewise, infrastructure measures capture risks associated with proximity to oil and gas pipelines and other hazardous technologies. Urban spatial structure is a surrogate for the quantity and quality of services that are important factors of vulnerability. Of course, natural factors are of the utmost importance. All single factors were weighted positively or negatively so that - in combination with other factors - they might intensify or reduce composite vulnerability; no single factor is pre-eminent. Composite vulnerability is therefore based on both absolute and relative factor values. This is an improvement over vulnerability analyses that do not take account of interaction among individual factors. For example, in this analysis, material adjustments to housing can counterbalance soil vulnerability.

Results

The general pattern of socio-economic vulnerability is shown in table 9.8 (column 1). The 16 Federal District delegaciones exhibit varied vulnerability: two high, four high - medium, eight low - medium, and two low. One of the high-vulnerability zones is part of the old city (the delegacion of Gustavo A. Madero). The other (Iztapalapa) has become heavily populated only recently, but is now fully urbanized. Three additional old- city neighbourhoods are ranked high - medium vulnerable and only one possesses low vulnerability (Benito Juz). The remaining low-vulnerability area is semi-rural Milpa Alta.

A similarly heterogeneous pattern shows up in the 58 municipios of the metropolitan zone: 5 high vulnerable, 11 high - medium, 11 medium, 16 low - medium and 15 low (table 9.10, column 1). The high-vulnerable municipios in the State of Mexico are located close to the Federal District's political boundaries. Industries, especially chemicals, are concentrated in three of them (Tlanepantla, Naucalpan, Ecatepec). Another unit (Netzahualcoytl) is a densely populated low-income residential area - a city within the city.

Table 9.8 General compound index of vulnerability of Mexico City

Delegacion

Socio-economic compound index

Urban spatial structure compound index

Regional infrastructure compound index

Natural (geographical, topographical, and geotechnical) compound index

General compound index

Alvaro ObregR>

4.0

4.0

4.0

5.0

4.3

Azcapotzalco

4.0

4.0

4.0

5.0

4.3

Benito Juz

1.0

1.0

1.0

5.0

2.0

CoyoacBR>

2.0

2.0

2.0

5.0

2.8

Cuajimalpa de Morelos

2.0

2.0

2.0

4.0

2.5

Cuauhtc

4.0

4.0

4.0

5.0

4.3

Gustavo A. Madero

5.0

5.0

5.0

5.0

5.0

Iztacalco

2.0

2.0

2.0

5.0

2.8

Iztapalapa

5.0

5.0

5.0

4.0

4.8

Magdalena Contreras, la

2.0

2.0

2.0

2.0

2.0

Miguel Hidalgo

2.0

2.0

2.0

5.0

2.8

Milpa Alta

1.0

1.0

1,0

1.0

1.0

Tlac

2.0

2.0

2.0

4.0

2.5

Tlalpan

2.0

2.0

2.0

1.0

1.8

Venustiano Carranza

4.0

4.0

4.0

5.0

4.3

Xochimilco

2.0

2.0

2.0

4.0

2.5

Mean

2.8

2.8

2.8

4.1

3.1

Sources: General Housing and Population Census, 1990; Economic Census of the State of Mexico, 1989; Annual Reports of the Government of the State of Mexico; Risk and Vulnerability Regional Study of the Valley of Mexico and its Metropolitan Zone, 1992.

Weighting: 5 = high; 4 = high-medium; 3 = medium; 2 = low-medium; 1 = low.

Table 9.9 General compound index of vulnerability, by degree of vulnerability (Mexico City)

Delegacion

General compound index

High vulnerability

Gustavo A. Madero

5.0

Iztapalapa

4.8

Venustiano Carranza

4.3

Cuauhtc

4.3

Azcapotzalco

4.3

Alvaro ObregR>

4.3

Low-medium vulnerability

Miguel Hidalgo

2.8

Iztacalco

2.8

CoyoacBR>

2.8

Xochimilco

2.5

Tlac

2.5

Cuajimalpa de Morelos

2.5

Low vulnerability

Magdalena Contreras, La

2.0

Benito Juz

2.0

Tlalpan

1.8

Milpa Alta

1.0

Mean

3.1

Sources: General Housing and Population Census, 1990; Economic Census of the State of Mexico, 1989; Annual Reports of the Government of the State of Mexico; Risk and Vulnerability Regional Study of Valley of Mexico and its Metropolitan Zone, 1992.

Within the Federal District, infrastructure has been weighted similarly to socio-economic factors. The District is a long-settled and maturely developed area whose infrastructure reflects the social make-up of its population (see table 9.8, column 3). The same cannot be said of the MCMZ. There, infrastructures are still being developed as informal settlements give way to more formal ones. As shown in table 9.10 (column 3), the infrastructure of 7 municipios is highly vulnerable, 18 are high - medium, 17 are low - medium, and 16 are low.

Table 9.10 General compound index of vulnerability of MCMZ

Municipio

Socio-economic compound index

Urban spatial structure compound indexa

Regional infrastructure compound index

Natural (geological, topographical, and geotechnical) compound index

General compound index

Acolman

2.0

3.0*

5.0

5.0

3.8

Amecameca

4.0

4.0

4.0

5.0

4.3

Apaxco

1.0

3.0*

4.0

1.0

2.3

Atenco

1.0

3.0*

4.0

5.0

3.3

Atizapan de Zaragoza

4.0

2.0

1.0

5.0

3.0

Atlautla

2.0

3.0*

2.0

2.0

2.3

Axapusco

3.0

3.0*

5.0

1.0

3.0

Ayapango

1.0

1.0*

4.0

1.0

1.8

Chalco

4.0

5.0

1.0

5.0

3.8

Chiautla

1.0

1.0*

1.0

5.0

2.0

Chicoloapan

3.0

2.0

1.0

2.0

2.0

Chiconcuac

1.0

1.0*

2.0

1.0

1.3

Chimalhuacan

4.0

5.0

2.0

5.0

4.0

Coacalco

4.0

2.0

5.0

5.0

4.0

Cocotitlan

1.0

1.0*

1.0

5.0

2.0

Coyotepec

2.0

2.0*

2.0

4.0

2.5

Cuautiltlan Izcalli

4.0

1.0

2.0

5.0

3.0

Cuautitlan

4.0

2.0

2.0

5.0

3.3

Ecatepec

5.0

4.0

5.0

5.0

4.8

Ecatzingo

2.0

1.0*

4.0

1.0

2.0

Huehuetoca

2.0

3.0*

4.0

1.0

2.5

Hueypoxtla

1.0

3.0*

1.0

1.0

1.5

Huixquilucan

3.0

1.0

2.0

5.0

2.8

Isidro Fabela

1.0

1.0*

1.0

2.0

1.3

Ixtapaluca

4.0

4.0

4.0

1.0

3.3

Jaltenco

2.0

3.0*

1.0

5.0

2.8

Jilotzingo

1.0

1.0*

1.0

2.0

1.3

Juchitepec

1.0

1.0*

4.0

1.0

1.8

Melchor Ocampo

2.0

3.0*

2.0

5.0

3.0

Naucalpan

5.0

1.0

1.0

5.0

3.0

Netzahualcoytl

5.0

2.0

2.0

5.0

3.5

Nextlalpan

1.0

1.0*

1.0

5.0

2.0

Nicolas Romero

4.0

4.0

1.0

4.0

3.3

Nopaltepec

2.0

1.0*

4.0

1.0

2.0

Otumba

3.0

3.0*

4.0

1.0

2.8

Ozumba

2.0

3.0*

1.0

1.0

1.8

Papalotla

2.0

1.0*

4.0

1.0

2.0

Paz, La

4.0

2.0

1.0

4.0

2.8

San Martin de las Piramides

3.0

1.0*

2.0

5.0

2.8

Tecamac

3.0

4.0

4.0

4.0

3.8

Temamatla

1.0

1.0*

2.0

5.0

2.3

Temascalapa

2.0

3.0*

1.0

1.0

1.8

Tenango del Aire

2.0

1.0*

4.0

1.0

2.0

Teoloyucan

3.0

3.0*

2.0

5.0

3.3

Teotihuacan

2.0

3.0*

5.0

2.0

3.0

Tepetlaoxtoc

2.0

3.0*

5.0

1.0

2.8

Tepetlixpa

1.0

1.0*

4.0

1.0

1.8

Tepotzotlan

3.0

3.0*

1.0

4.0

2.8

Tequixquiac

1.0

3.0*

2.0

1.0

1.8

Texcoco

4.0

2.0

2.0

5.0

3.3

Tezoyuca

1.0

1.0*

2.0

5.0

2.3

Tizayuca, HIDALGO

2.0

3.0*

2.0

5.0

3.0

Tlalmanalco

3.0

3.0*

4.0

2.0

3.0

Tlalnepantla

5.0

4.0

5.0

5.0

4.8

Tultepec

3.0

3.0*

2.0

5.0

3.3

Tultitlan

5.0

4.0

4.0

5.0

4.5

Villa del Carbon

2.0

3.0*

4.0

5.0

3.5

Zumpango

3.0

4.0

4.0

5.0

4.0

Mean

2.6

2.4*

2.7

3.4

2.8

Sources: General Housing and Population Census, 1990; Economic Census of the State of Mexico, 1989; Annual Reports of the Government of the State of Mexico; Risk and Vulnerability Regional Study of Valley of Mexico and its Metropolitan Zone, 1992.

Weighting: 5 = high; 4 = high-medium; 3 = medium; 2 = low-medium; 1 = low.

a. Figures with an asterisk are estimates based on limited information.

Urban structure illustrates a contrasting pattern (tables 9.8 and 9.10, column 2). Chalco - which was among the least vulnerable units according to measures of infrastructure development - now has the highest level of vulnerability (table 9.10, column 2). Of 20 municipios that are sufficiently urbanized to make an assessment, only 2 have a high level of vulnerability; 8 are high - medium, 1 medium, 6 low - medium, and 3 low. Ecatepec and Tlalnepantla are the municipios that are now most developed but they still show high - medium levels of vulnerability because the process of urbanization is far from complete. Naucalpan, on the other hand, is characterized by low vulnerability on this factor. Surprisingly, the recently created low-income residential area of Netzahualcoytl exhibits only medium - low vulnerability.

The natural hazard dimensions of the enumeration units comprise the final assessment factor. Within the Federal District, vulnerability is relatively homogeneous: 9 out of the 16 spatial units have high vulnerability, 4 high - medium, 1 low - medium, and only 2 low (table 9.8, column 4). A combination of soft subsoils and seismic risks accounts for the elevated vulnerability. Central delegaciones are particularly at hazard. Further more, these units are densely populated and heavily built up. The two delegaciones with low vulnerability, Tlalpan and Milpa Alta, have only recently been incorporated into the urban area. They retain many fields and open spaces. The overall level of vulnerability in the MCMZ area is similar to that of the city but for different reasons. Most of the municipios (29) are highly vulnerable, though 18 possess low vulnerability (table 9.10, column 4).

Compound vulnerability scores and spatial patterns have been constructed by combining the separate indices discussed above (tables 9.8 and 9.10, column 5). Six delegaciones are highly vulnerable, all located in the central historic city. Gustavo A. Madero delegacion tops the list. If this preliminary finding is borne out by more detailed studies, such places deserve to become the focus of effective vulnerability-reduction programmes. However, these are very large delegaciones that exhibit considerable internal heterogeneity, and finer-grained assessments are probably warranted. In contrast, only one of the central delegaciones in the Federal District has a low degree of vulnerability (Benito Juz). Other low-vulnerability units (Magdalena Contreras, Tlalpan, and Milpa Alta) are all located on the southern fringe of the city, on seismically stable soils (tables 9.8 and 9.9).

There is a wider range of compound vulnerability in the MCMZ (tables 9.10 and 9.11 and fig. 9.3). Ten municipios are highly vulnerable, 17 high - medium, 7 medium, 14 low - medium, and 10 low. The highly vulnerable group includes places that are adjacent to the city (Tlalnepantla, Ecatepec), as well as others that are not fully urbanized and contiguous to the city. Chalco municipio is included in this category. Other municipalities adjacent to the city, Netzahualcoytl and Naucalpan, which might be expected to have the same ranking, have only a high - medium vulnerability. All municipios in the low-vulnerability category are loosely attached to the mega-city and are only tenuously integrated into its functions. They contain much agricultural land and little industry.

Table 9.11 General compound index of vulnerability, by degree of vulnerability (MCMZ)

Municipio

General compound index

High vulnerability

Tlalnepantla

4.8

Ecatepec

4.8

Tultitlan

4.5

Amecameca

4.3

Zumpango

4.0

Coacalco

4.0

Chimalhuacan

4.0

Tecamac

3.8

Chalco

3.8

Acolman

3.8

High-medium vulnerability

Villa del Carbon

3.5

Netzahualcoytl

3.5

Tultepec

3.3

Texcoco

3.3

Teoloyucan

3.3

Nicolas Romero

3.3

Ixtapaluca

3.3

Cuautitlan

3.3

Atenco

3.3

Tlalmanalco

3.0

Tizayuca, HIDALGO

3.0

Teotihuacan

3.0

Naucalpan

3.0

Melchor Ocampo

3.0

Cuautiltlan Izcalli

3.0

Axapusco

3.0

Atizapan de Zaragoza

3.0

Medium vulnerability

Tepotzotlan

2.8

Tepetlaoxtoc

2.8

San Martin de las Piramides

2.8

Paz, La

2.8

Otumba

2.8

Jaltenco

2.8

Huixquilucan

2.8

Low-medium vulnerability

Huehuetoca

2.5

Coyotepec

2.5

Tezoyuca

2.3

Temamatla

2.3

Atlautla

2.3

Apaxco

2.3

Tenango del Aire

2.0

Papalotla

2.0

Nopaltepec

2.0

Nextlalpan

2.0

Ecatzingo

2.0

Cocotitlan

2.0

Chicoloapan

2.0

Chiautla

2.0

Low vulnerability

Tequixquiac

1.8

Tepetlixpa

1.8

Temascalapa

1.8

Ozumba

1.8

Juchitepec

1.8

Ayapango

1.8

Hueypoxtla

1.5

Jilotzingo

1.3

Isidro Fabela

1.3

Chiconcuac

1.3

Mean

2.8

Sources: General Housing and Population Census, 1990; Economic Census of the State of Mexico, 1989; Annual Reports of the Government of the State of Mexico; Risk and Vulnerability Regional Study of Valley of Mexico and its Metropolitan Zone, 1992.

How do the results of this vulnerability analysis differ from more conventional ones that rely solely on natural hazard factors? If only natural factors are used, more than half of the MCMZ's area is classified as highly vulnerable. When social, economic, and other factors are added, the high-vulnerability area is reduced to about one-third of the mega-city and lands that were formerly designated as high vulnerable are reclassified as of low vulnerability. The high vulnerability of industrial zones is reinforced, but major changes occur in northern and central parts of the MCMZ. Conversely, the south of the city is revealed as an area of low vulnerability. However, there is also no obvious correlation between disadvantaged socio-economic conditions and high vulnerability.


Fig. 9.3 General compound index of vulnerability of the mega/city of Mexico

Conclusions

Modern Mexico City has been created by three main groups that interact in complex and highly dynamic ways: real estate investors and developers, the state, and the poor. The process of interaction has, in fact, produced two cities. These can be labelled the formal and the informal cities, or the solvent and the insolvent, but, by whatever name they are known, each of them is subject to a different type of vulnerability. To a greater or lesser degree the same is true of other mega-cities in developing countries. Unless this dichotomy is understood and attempts are made to eliminate it, polarization will not diminish, growing numbers of people will continue to be vulnerable to worsening hazards, and the mega-cities will continue to be dysfunctional places.

The state has the greatest responsibility to develop urban hazard action plans that are, at the same time, internally coherent and efficient, externally adjusted to changing global economic and political arrangements, and responsive to the needs of diverse public and private interest groups. But states have often resisted adopting comprehensive urban planning procedures, thereby helping to increase the vulnerability of mega-cities. Herein lies a true paradox; at a time when governmental intervention in human affairs is often considered to be excessive, the empirical evidence of hazard in third world mega-cities demonstrates that public intervention to protect life, livelihood, and property has actually been insufficient, doubtful, erratic, and always late in coming. The alternative - market-driven forces - has been dominant for the past 40 years and has produced cities that are anarchic, dysfunctional, and unequal.

Whatever planning exists is largely confined to the formal city, yet the city's vulnerability is principally conditioned by the laws of supply and demand. These have generally worked to produce lower levels of vulnerability. In contrast, the informal city is illegal and therefore unplanned. It also typically possesses higher levels of vulnerability. But it is precisely the informal city that requires strict planning. We cannot permit human settlements to be created in areas that are vulnerable to geomorphic hazards. Such actions are socially unjust and fiscally irresponsible. Human life and well-being are directly at risk and sooner or later the state will be forced to bear an increased financial burden for the infrastructure that will eventually be required to offset these risks.

States must give high priority to urban planning and must treat it as a coordinating function that bridges all other sectors of society, not - as is so often the case in developing countries - as a separate sector. The task of planning is becoming more difficult because mega-cities are fragmenting into different political-administrative entities whose leaders frequently lose sight of the needs of the whole community. Nevertheless, the essential unity of the mega-city is indisputable, although sometimes it is camouflaged by substantive complexity. In order to reduce urban hazards, mega-city governments require, at a minimum, the capacity to coordinate decisions about land use and urban functions within their boundaries. This implies the formulation of strategies of metropolitan development and the establishment of permanent processes of mega-city planning and management.

This chapter has emphasized social and legal issues because it is necessary to come to grips with the social forces that underlie vulnerability to hazards. Nature is sometimes susceptible to the actions of humans, who can generate catastrophes by destabilizing some natural processes. But we must also remember that other natural processes are not necessarily subordinate to social ones. The social and natural causes of natural disasters should both be accommodated in the urban planning process. What is needed is a new axiology or a new ethic to guide the management of mega-city hazards. Such an ethic might take its cue from the concept of sustainable development - a merging of economic and environmental planning in pursuit of long-term sustainability. In the pursuit of sustainable development, the mega-city may make itself less artificial; indeed, it may come to acquire its own nature.

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