From the Federal Response Plan at http://www.ohsep.louisiana.gov/plans/frp2003.pdf
Most disasters and emergencies are handled by State and local responders. The Federal Government is called on to provide supplemental assistance when the consequences of a disaster exceed State and local capabilities. If needed, the Federal Government can mobilize an array of resources to support State and local efforts. Various emergency teams, support personnel, specialized equipment, operating facilities, assistance programs, and access to private-sector resources constitute the overall Federal disaster operations system. The FRP describes the major components of the system, as well as the structure for coordinating Federal response and recovery actions necessary to address State-identified requirements and priorities.