Approximately, 75,000 people live in areas prone to volcanic hazards and floods in the large city of Arequipa, Peru. We have conducted three different surveys involving c. 280 respondents to appraise the socio-economic characteristics of urban dwellers living in informal settlements along two ravines, the extent to which they know hazards, perceive risk, and how they behave in case of disaster. This study also assesses how local communities consider, and civil authorities implement mitigation procedures in the city. The statistical analysis of the survey datasets included univariate, bivariate, and multivariate techniques together with hierarchical agglomerative clustering. Low-income urban dwellers, with a minimum or without education, represent almost 32% of the vulnerable population living in four districts. Almost 45% of the respondents have a regular to minimum knowledge of hazards, and half of the population is worried or uncertain about volcano and debris flow threats. A large proportion of dwellers trust early warning messages, but almost half of them check them out before evacuating. Overall, between a third and half of people living in the four most exposed districts of Arequipa seem to be quite vulnerable in case of an imminent debris flow. Interviews and focus groups with risk managers aimed to understand why planning emergency operations and risk mitigation are not as efficient as the municipality, and the communities would expect in Arequipa. Several issues hinder an adequate disaster risk management, as the underlying vulnerability factors of the exposed population are not accounted for. Under-investment in disaster risk management has led to diminish accountability among the risk managers and involvement of dwellers.