The Importance of Infrastructure Interdependencies was Highlighted in 1998 when the President's Commission on Critical Infrastructure Protection recognized that the security, economic prosperity and social well-being of the nation depend on the reliable functioning of our increasingly complex and interdependent infrastructures. These include electric systems, gas and oil systems, water-supply and wastewater systems, communications, transportation, banking and finance, and emergency and government services.

The commission also noted that “mutual dependence and interconnectedness made possible by the information and communications infrastructure lead to the possibility that our infrastructures may be vulnerable in ways they never have been before.” Failure to understand how disruptions to one infrastructure could cascade to others worsen response and recovery efforts, or result in common-cause failures that can leave operators and emergency-response personnel unprepared to deal effectively with the impacts of such disruptions.

Understanding, analyzing and sustaining resilience of the electric and other interdependent infrastructures require modeling tools to assess the technical, economic and security implications of technology and policy decisions designed to ensure their reliability and security.

THE CHANGING WORLD

Historically, interdependencies have been considered to be either physical or geospatial in nature. An example of a physical interdependence is that the water-supply infrastructure depends on electric power to operate its pumps, while at the same time, the electric power infrastructure must have water to make steam and cool its equipment. Geospatial interdependencies arise when infrastructure components, e.g., transmission lines, water pipelines, gas pipelines and telecommunications cables, share common corridors, thus increasing the vulnerabilities to and consequences from disasters in the same geographic area.

However, the proliferation of information technology and the reliance on the open marketplace for purchasing and selling infrastructure commodities and services has linked infrastructures in new and complex ways and has created new vulnerabilities. This trend is also driven by the increased usage of automated monitoring and control systems such as distribution automation and supervisory control and data acquisition systems. The dependence of the new energy marketplace on the Internet and other e-commerce systems and the complicated links to financial markets highlight the breadth of cyber and logical interdependencies.

GEOSPATIAL CHARACTERISTICS

Infrastructures are geospatially interdependent if a local environmental event can create state changes in all of them. Geospatial interdependency occurs when elements of multiple infrastructures are in close spatial proximity. Given this proximity, events such as an explosion or fire could create correlated disturbances or changes in these geographically interdependent infrastructures. Such correlated changes are not due to physical or cyber connections between infrastructures; rather, they arise from the influence the event exerts on all the infrastructures simultaneously.

For example, an electrical line and communication cable hung under a bridge connect (geospatial) elements of the electric power, telecommunications and transportation infrastructures. The interdependency in these cases is due to proximity; the state of one infrastructure does not influence the state of another. Traffic across the bridge does not influence the flow of electricity or transmission of communications. Because of the close spatial proximity, however, physical damage to the bridge could create correlated disruptions in the electric power, communications and transportation infrastructures. Some interdependencies and their effects on infrastructure operations are caused by physical phenomena, whereas others result from human intervention and errors.

ELECTRIC INFRASTRUCTURE INTERDEPENDENCIES

As mentioned above, electric systems can have several interdependencies with other infrastructure that must be considered when identifying critical infrastructure and their interdependencies, when developing response plans and in addressing other issues of security and protection. In addition, emergency services and emergency-response activities are heavily dependent on electric services. Beyond emergency services, many other sectors and services such as finance, banking, business, industry, government services and military are also dependent on electric infrastructure.

As the president's commission pointed out 10 years ago, electric infrastructure is highly connected and independent infrastructure for both business and economy security.

Dave DiSera is GITA's research committee chair and past president and vice president. He serves as the CIO of First Insurance Co. of Hawaii. david.disera@ficoh.com