6 U.S.C. § 311 - U.S. Code - Unannotated Title 6. Domestic Security § 311. Definitions
(3) the term “catastrophic incident” means any natural disaster, act of terrorism, or other man-made disaster that results in extraordinary levels of casualties or damage or disruption severely affecting the population (including mass evacuations), infrastructure, environment, economy, national morale, or government functions in an area;
https://codes.findlaw.com/us/title-6-domestic-security/6-usc-sect-311.html
6 U.S.C. § 318 - U.S. Code - Unannotated Title 6. Domestic Security § 318. National Advisory Council
…the Secretary shall establish an advisory body under section 451(a) of this title to ensure effective and ongoing coordination of Federal preparedness, protection, response, recovery, and mitigation for natural disasters, acts of terrorism, and other man-made disasters…
https://codes.findlaw.com/us/title-6-domestic-security/6-usc-sect-318.html
42 U.S.C. § 5121 - U.S. Code - Unannotated Title 42. The Public Health and Welfare § 5121. Congressional findings and declarations
(a) The Congress hereby finds and declares that–
(1) because disasters often cause loss of life, human suffering, loss of income, and property loss and damage; and
(2) because disasters often disrupt the normal functioning of governments and communities, and adversely affect individuals and families with great severity;
special measures, designed to assist the efforts of the affected States in expediting the rendering of aid, assistance, and emergency services, and the reconstruction and rehabilitation of devastated areas, are necessary.
…
https://codes.findlaw.com/us/title-42-the-public-health-and-welfare/42-usc-sect-5121.html
42 U.S.C. § 1201 - U.S. Code - Unannotated Title 42. The Public Health and Welfare § 1201. Authorization of appropriations
For the purpose of enabling each State to furnish financial assistance, as far as practicable under the conditions in such State, to needy individuals who are blind, there is hereby authorized to be appropriated for each fiscal year a sum sufficient to carry out the purposes of this subchapter. The sums made available under this section shall be used for making payments to States which have submitted, and had approved by the Secretary of Health and Human Services, State plans for aid to the blind.
https://codes.findlaw.com/us/title-42-the-public-health-and-welfare/42-usc-sect-1201.html