Critical Infrastructure Protection in Homeland Security: Defending a Networked Nation, 2nd Edition

4 Complex CIKR Systems

A complex CIKR system is a collection of components or parts—CIKR assets—that are interrelated, interdependent, and linked through many interconnections and behave as a unified whole in adapting to changes in the environment.¹ Generally, these systems appear simple on the surface, but often turn out to behave in complex ways due to six major environmental factors: threat, efficiency, regulation, cost, NIMBY, and demand or load on the system. The dynamic interaction among CIKR assets and these environmental factors is what makes complex CIKR systems complex.

The complexity theory is especially useful for the study of CIKR, because most infrastructure systems appear to be simple structures—roads, bridges, pipelines, power lines, communication links, transportation networks, etc.—but in practice, they have been found to behave like well-known complex systems. They evolve over long periods of change, shifting from initially disordered collections of assets toward greater order and structure as they adapt to efficiency and optimization forces. They often behave in an unexpected—long-tailed—manner, and when under stress, they fail like the metaphorical sand pile. While their behavior under stress is unpredictable, they almost always obey a power law, as described in the previous chapter.

Complexity provides a unified theory for understanding and fixing fragile CIKR. In particular, this chapter develops several key metrics that give great insight into what ...