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6 U.S. Code § 745 - National planning scenarios

(a) In general

The Administrator, in coordination with the heads of appropriate Federal agencies and the National Advisory Council, may develop planning scenarios to reflect the relative risk requirements presented by all hazards, including natural disasters, acts of terrorism, and other man-made disasters, in order to provide the foundation for the flexible and adaptive development of target capabilities and the identification of target capability levels to meet the national preparedness goal.

(b) DevelopmentIn developing, revising, and replacing national planning scenarios, the Administrator shall ensure that the scenarios—
reflect the relative risk of all hazards and illustrate the potential scope, magnitude, and complexity of a broad range of representative hazards; and
provide the minimum number of representative scenarios necessary to identify and define the tasks and target capabilities required to respond to all hazards.