In recent years, awareness of the potential consequences associated with a major disruption to the critical infrastructure has grown among public and private entities. Indeed, traditional and emerging threats endanger service continuity and, by extension, the normal functioning of modern society. This paper presents an approach for modeling the effects of critical infrastructure failures as a result of unexpected events. The transportation, energy and telecommunications infrastructures are modeled using a system dynamics approach. The work constitutes a component of the CRISADMIN Project that is focused on developing a tool to evaluate the impacts of critical events. The ultimate objective of the project is to provide decision makers with a sophisticated tool to help them mitigate negative effects in emergency situations. The prototype tool described in this paper leverages case studies of terrorist attacks and floods that have occurred in Europe.