Upon the happening of any emergency caused by violence of nature, casualty, riot, insurrection, war, or other unanticipated occurrence requiring the immediate preservation of order or public health, or for the property which has been damaged or destroyed by accident, or for public relief from calamity, or in settlement of approved claims for personal injuries or property damages, or to meet mandatory expenditures required by law enacted since the last budget was adopted, or to cover expenses incident to preparing for or establishing a new form of government authorized or assumed after adoption of the current budget, including any expenses incident to selection of additional or new officials required thereby, or incident to employee recruitment at any time, the city legislative body, upon the adoption of an ordinance, by the vote of one more than the majority of all members of the legislative body, stating the facts constituting the emergency and the estimated amount required to meet it, may make the expenditures therefor without notice or hearing.