Social and environmental vulnerability in Southeast Brazil associated with the South Atlantic Convergence Zone

The South Atlantic Convergence Zone (SACZ) is an atmospheric phenomenon, typical of summertime, in which a band of nebulosity may cause intense or persistent rainfall in many regions of Brazil. The association between this natural event and human interventions is a major factor for the occurrence of social and environmental impacts such as floods, flash floods, inundations, and landslides. In this work, we objectively quantify the relationship between the SACZ and the incidence of natural hazards in Southeast Brazil from 1995 to 2016. We use official records of disasters, from the digital archive of the Integrated Disaster Information System (S2ID) and time series of SACZ events, to calculate conditional probabilities of SACZ events, given the occurrence of disasters in the states of Southeast Brazil. We also analyze which types of natural disaster are most prevalent during SACZ events. The average probability of disaster occurrence, given the presence of the SACZ in the Southeast Brazil, is 24%, while the average conditional probability of SACZ occurrence, given a disaster in the Southeast, is 48%. For each state in Southeast Brazil, the probabilities are higher for Espirito Santo (60%), followed by Minas Gerais (50%), Rio de Janeiro (40%) and Sao Paulo (31%). These results evidence the vulnerability of Southeast Brazil associated with intense or persistent rainfall typical of the SACZ phenomenon.