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Investigaciones geográficas

versão On-line ISSN 2448-7279versão impressa ISSN 0188-4611

Resumo

PONCE-PACHECO, Ana B.  e  NOVELO-CASANOVA, David A.. Vulnerability and Risk in Valle de Chalco Solidaridad, Estado de Mexico, Mexico. Case Study: El Triunfo, Avandaro and San Isidro. Invest. Geog [online]. 2018, n.97, 00011. ISSN 2448-7279.  http://dx.doi.org/10.14350/rig.59675.

Irregular communities established in the border of large cities usually have high levels of vulnerability and in some cases, the exposure to natural and man-made hazards result in great damage to these populations. Valle de Chalco Solidaridad (VCS) is an example of this kind of communities. VCS is a municipality in the State of Mexico, Mexico, located in the old Chalco Lake to eastern of Mexico City. The natural environment of VCS has been dramatically modified because of the overexploitation of the local aquifer that has caused subsidence in most of its territory.

Floods are also common in VCS, mainly associated to failures of the walls of the local wastewater canal called “La Compañía” (LCC) causing severe damage to the local population. Thus, the most common local hazards are subsidence and flooding although because of its geographical location, VCS is also prone to the impact of large earthquakes from the Mexican subduction zone. LCC was an open-air sewage canal that collects domestic water from two municipalities in the State of Mexico: Valle de Chalco Solidaridad and Chalco. At present, LCC is a piped sewage canal.

On 2000, 2005, and 2010, districts of VCS were severely damaged due to failures of LCC. The objective of this study is to estimate the levels of vulnerability and risk to floods of VCS. To complete our work, we also considered the vulnerability and risk to earthquakes and subsidence. Our research was constrained to the communities of El Triunfo, San Isidro, and Avandaro by considering independent assessments of the social, economic and structural vulnerabilities as well as of the global vulnerability. We adapted the Community Vulnerability Assessment Tool (CVAT) developed by the National Oceanic and Atmospheric Administration (NOAA) to estimate vulnerability. Data for our research was collected from field works on March-April 2010, and from scientific and governmental sources. In our study we considered global vulnerability as the average of the social, economic and structural vulnerabilities. The spatial distributions of each studied vulnerability was represented in a Geographic Information System (GIS) considering five levels of vulnerability: very low, low, moderate, high and very high.

For the social vulnerability we evaluated aspects like communication among neighbors, social characteristics of the population such as age, disability and education level. For the economic vulnerability we considered elements like income, economical dependence and main economic activity of the family. For the structural vulnerability we took into account construction material, structural reinforcements, geometry of construction, number of stories, among other factors. The spatial distribution of risk was determined superposing the local GIS flood, seismic, and subsidence hazard-map layers over the global vulnerability map. Risk was characterized by using the same five levels of vulnerability. These risk maps allow us to identify those priority areas to implement mitigation actions.

Our methodology can be considered as a first approximation of risk and provides a qualitative tool to support civil protection authorities to develop a disaster prevention program as well as to implement public policies for risk mitigation. Our results indicate that the majority of the population of VCS has moderate and high levels of social vulnerability and that practically all territory has high and very-high economic vulnerability. Most households in the study area have moderate and high level of structural vulnerability. About one third of the studied population is in high and very high risk to flooding. Seismic and subsidence risks are moderate and high, respectively.

Small areas have moderate global vulnerability. High and very high flood risk is constrained to those families located near the high-risk flooding areas. The factors that were identified that increase vulnerability in VCS are: 1) Lack of knowledge about the existing levels of local hazards; 2) Poor structural housing conditions; 3) Failures of LCC’s infrastructure; and 4) High exposure of vulnerable people.

Our methodology allows determining the spatial distribution of vulnerability and risk. However, for a complete analysis, it is necessary additional studies to assess those factors that condition the social construction of risk. The results of this work identify those areas where mitigation measures are needed and provide the basis for decision makers to implement risk reduction actions in VCS. We also believe in the need for developing a program to reduce structural vulnerability to both, earthquakes and floods. For the urban development planning of VCS, subsidence and earthquake risks should also be taken into account. Thus, the development of public policies for risk prevention and mitigation are also required.

Palavras-chave : Vulnerability; Risk; Risk Management; Risk assessment; Valle de Chalco Solidaridad.

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