Abstract — Modern society depends on the operations of civil infrastructure systems, such as transportation, energy, telecommunications and water. Clearly, disruption of any of these systems would present a significant detriment to daily living. However, these systems have become so interconnected, one relying on another, that disruption of one may lead to disruptions in all. The focus of this research is on developing techniques which can be used to respond to events that have the capability to impact interdependent infrastructure systems. As discussed in the paper, infrastructure interdependencies occur when, due to either geographical proximity or shared operations, an impact on one infrastructure system affects one or more other infrastructure systems. The approach is to model the salient elements of these systems and provide decision makers with a means to manipulate the set of models, i.e. a decision support system. 1

Abstract: This study investigates impacts of the 2001 World Trade Center attack on critical infrastructure systems in the New York City metropolitan area. Of particular interest are the physical or logical connections—also known as interdependencies—among these systems, and the impacts of the attack on them. This study extends knowledge about the behavior of complex and interdependent infrastructures systems following a significant disruption. The results depict impact to all infrastructure systems as a result of the attack, with disruptions reported throughout the 3 month study period. Approximately 20 % of these disruptions involved interdependencies, and a majority of infrastructure systems were involved in at least one interdependency. The results therefore suggest that interdependence is a pervasive condition of New York City’s critical infrastructures. Accordingly, approaches to planning for and managing infrastructure-related disruptions, particularly those involving interdependency, are discussed.