Upon the happening of any emergency caused by fire, flood, explosion, storm, earthquake, epidemic, riot, or insurrection, or for the immediate preservation of order or of public health or for the restoration to a condition of usefulness of any public property the usefulness of which has been destroyed by accident, or for the relief of a stricken community overtaken by a calamity, or in settlement of approved claims for personal injuries or property damages, exclusive of claims arising from the operation of any public utility owned by the county, or to meet mandatory expenditures required by any law, the board of county commissioners may, upon the adoption by the unanimous vote of the commissioners present at any meeting the time and place of which all of such commissioners have had reasonable notice, of a resolution stating the facts constituting the emergency and entering the same upon their minutes, make the expenditures necessary to meet such emergency without further notice or hearing.