Congressional Primer on Responding to Major Disasters and Emergencies [September 13, 2018] [open pdf - 927KB]
"The principles of disaster management assume a leadership role by the local,state, and tribal governments affected by the incident. The federal government provides coordinated supplemental resources and assistance, only if requested and approved. The immediate response to a disaster is guided by the National Response Framework (NRF), which details roles and responsibilities at various levels of government, along with cooperation from the private and nonprofit sectors, for differing incidents and support functions. A possible declaration of a major disaster or emergency under the authority of the Robert T. Stafford Disaster Relief and Emergency Assistance Act (the Stafford Act,P.L. 93-288, as amended) must, in almost all cases, be requested by the governor of a state or the chief executive of an affected Indian tribal government, who at that point has declared that the situation is beyond the capacity of the state or tribe to respond. The governor/chief also determines for which parts of the state/tribal territory assistance will be requested, and suggests the types of assistance programs that may be needed. The President considers the request, in consultation with officials of the Federal Emergency Management Agency (FEMA), within the Department of Homeland Security (DHS), and makes the initial decisions on the areas to be included as well as the programs that are implemented."
CRS Report for Congress, R41981
Congressional Research Service: https://crsreports.congress.gov/