Congressional Primer on Responding to and Recovering from Major Disasters and Emergencies [Updated June 3, 2020] [open pdf - 1MB]
From the Overview: "Before and after a disaster strikes, it is useful to understand the basic national emergency management structure and where authority rests at various stages of the process. This report provides information to aid policymakers as they navigate the phases of disaster response and recovery and the associated actions, and entity responsibilities. Additionally, it describes the laws and administrative policies governing the disaster response and recovery processes. The report also reviews the legislative framework that exists for providing federal financial assistance following a presidential declaration of emergency or major disaster, as well as the policies the executive branch employs to provide supplemental help to state, territorial, Indian tribal, and local governments during and following disasters."
CRS Report for Congress, R41981
Congressional Research Service: https://crsreports.congress.gov/