The following definitions apply to this part:
(a) Emergencies. These are conditions which affect public welfare and occur as a result of enemy attack, insurrection, civil disturbances, earthquake, fire, flood, or other public disasters which endanger life and property or disrupt the usual process of government. The term ``emergency'' includes any or all of the conditions explained in this section.
(b) Civil defense emergency. This is a disaster situation resulting from devastation created by an enemy attack and requiring emergency operations during and following attack. It may also be proclaimed by appropriate authority in anticipation of an attack.
(c) Civil disturbances. These are group acts of violence or disorder prejudicial to public law and order including those which follow a major disaster. They include riots, acts of violence, insurrections, unlawful obstructions or assemblages, or other disorders.
(d) Major disaster. Any flood, fire, hurricane, or other catastrophe which, in the determination of the President, is or threatens to be of sufficient severity and magnitude to warrant disaster assistance by the Federal Government to supplement the efforts and available resources of the State and local governments in alleviating the damage, hardship, or suffering caused thereby.