Vulnerability and risk to intense rainfall in Mexico: The effect of land use cover change

Résumé 0

"Natural disasters should be examined within a risk-perspective framework where both natural hazards and vulnerability are considered. The trend toward more frequent floods in Mexico in recent decades is not only the result of more intense rainfall, but also a consequence of increased vulnerability. As a multifactorial element, vulnerability is a low-frequency modulating factor of the risk dynamics to intense rainfall. It can be described in terms of physical, social and economical factors. For instance, deforested or urbanized areas are the physical and social factors that lead to the deterioration of watersheds and an increased vulnerability to intense rains. Increased watershed vulnerability due to land-cover changes is the primary factor leading to more floods, particularly over south-central Mexico. Only in some parts of the country, such as Baja California Sur, the increased frequency of intense rainfall (i.e., natural hazard) associated with high-intensity tropical cyclones is the leading cause of more frequent floods. We have developed a methodology to estimate flood risk associated with heavy rainfall considering changes in land cover and use, terrain slope and basin compactness are key vulnerability factors. The capability of the flood-risk model for Mexico was tested by comparing the observed and modeled frequency of floods for the 1970-2010 period. It was found that over most of the Mexican territory, more frequent floods are the result of a rapid deforestation process. Consequently, flood-risk management should include structural measures, such as watershed restoration and land cover – use planning."