A comprehensive methodology for the evaluation of infrastructure interdependencies

Nowadays infrastructure networks are the basis of life and economy of every community, large or small. These infrastructures have always a certain degree of interdependency among them. This means that when the community is subjected to a shock (earthquake, terrorism, hurricanes, floods, etc.) it is more vulnerable when the degree of interdependency among infrastructures is higher. In this article, after defining a reference nomenclature based on the analysis of the literature in the field and after identifying a total of sixteen type of infrastructures that compose each community: seven core infrastructures (Electricity, Oil delivery, Transportation, Telecommunication, Natural Gas delivery, Water supply, Wastewater treatment) and nine no-core infrastructures (Financial system, Building services, Business, Emergency services, Food supply, Government, Health care, Education, Commodities), we propose a method of analysis of the degree of interdependency among the various members of the community infrastructure. Using a matrix approach, an index is evaluated that takes into account the effect that any infrastructure can induce on another subordinated to it. This index depends on the type of failure that an infrastructure may cause to another one (coupled and uncoupled) and on the number of systems affected. From the matrix display is then possible understanding what are the most important infrastructures for the community and then focus all the efforts to reduce wherever possible the degree of interdependency and/or restore them as quickly as possible in the case of a partial or total disruption.