This research analyzes the relationship between the city of Santiago de Chile and the Mapocho River as a space for risks and threat during the 18th century. In order to do this, we observed the responses of the population and the civil and ecclesiastical authorities against the dangers of the river when the city was the scene of several threats such as diseases, droughts, rains, fluvial floods and the melting of the Cordillera. We have used various sources such as travelers' reports, official communications, technical reports, the debates of the Cabildo de Santiago, and printed works contemporary to the studio. The results allow us to conclude that the episodes of floods, droughts and epidemic outbreaks transformed the Mapocho River into a geosymbol for disasters in the social and institutional images of the city.