Specific areas of authority and responsibilities for emergency management should be clearly stated in local ordinances and laws. These ordinances and laws should specify a specific line of succession for elected officials and require that departments of government establish lines of succession.

FEMA IS-100.C: Introduction to the Incident Command System, ICS 100 Answers

Here are the FEMA IS-100.C: Introduction to the Incident Command System, ICS 100 Answers

Here are the FEMA IS-230.D: Fundamentals of Emergency Management Answers