|Vulnerability and Risk Assessment - 2nd Edition (Department of Humanitarian Affairs/United Nations Disaster Relief Office - Disaster Management Training Programme - United Nations Development Programme , 1994, 70 p.)|
|Part 2 - Assessing risk and vulnerability|
Reducing disaster risk in Mexico City "vecindades"
Human vulnerability assessment
From the analysis of damage after the earthquake that affected Mexico City in 1985 and after detailed geotechnical studies it was established that patterns of future earthquake hazard were likely to be concentrated in and around the historic center of Mexico City. The very high occupancy rates of many of the more vulnerable buildings in the town center by low-income households was a matter of concern. The assessment of buildings most at risk (Case Study Part A, pages 35 and 36) identifies a number of very high occupancy, highly vulnerable buildings. Understanding the social and economic context of the risk is essential to the design of a suitable risk mitigation program.
A systematic survey, interviewing a sample of the residents of the area, enabled a social and economic profile to be built up of the community at risk.23 This was carried out through neighborhood surveys, building use surveys and household interview questionnaires. Consultations were held with many of the occupants of the buildings identified as being at risk.
Economic profile of community at risk
A summary of some of the key characteristics of the community at risk is shown on the next page. This community is a low-income community with 60% of the households on an income less than the legislated minimum wage. Most of the community are street traders - the city center is a focus of street markets for the suburban population who travel in to the center to buy. This is a very flexible and insecure form of employment, dependent on a variable market. Many incomes are supplemented by cottage industry - simple manufacturing, sewing etc., carried out in the home. These incomes would be severely affected by damage to homes and to any damage to the city center which would dissuade the market customers from visiting.
Socio-demographic profile of community at risk
The families are large for an urban area - 60% of the households have 5 or more members. Accommodation in the vecindades is extremely cramped - most families have one or two-roomed apartments, occasionally split-level with makeshift mezzanine for extra sleeping space. Single parent families (mainly mothers) are common, about a third of all households. Many families have young children. In earthquakes young children and women are more vulnerable as they spend more time inside the home.
The low-income families are mainly concentrated in very high occupancy tenement buildings. The occupancy profile shows that a small percentage of the buildings have very high numbers of residents - in the hundreds. These concentrations of the population make them extremely vulnerable to earthquakes - the collapse of any one of these very densely occupied buildings would cause a disaster on its own. Conversely, it means that a mitigation program to protect a large number of people can focus on a relatively small number of buildings (identified in Part A of the case study). Nearly all the households most at risk live in rented accommodation. Rent-freeze laws mean that landlords receive very little rental revenue and maintenance of the buildings is minimal, as is the provision of basic services.
Actions to reduce vulnerability
A trust fund to facilitate housing upgrading in the city center has been established by special legislation and will be financed through property development taxation in other parts of the city. The fund will be used largely to encourage private sector finance in housing upgrading. Some of the worst vecindades could be expropriated under compulsory purchase powers established in the earthquake reconstruction. Expropriated vecindades would be refurbished and managed by a tenants cooperative. The budget available for the upgrading is small and it is important that spending is used to maximize the effect it would have in reducing future earthquake risk. How many buildings should have such intervention and what would be the effect?
The assessment of the benefits of possible building upgrading strategies are discussed in Part C of this case study.