Neb. Rev. Stat. §§ 14-508
Neither the city council nor any officer of a city of the metropolitan class shall expend or incur obligations for the expenditure of more money than has been provided and appropriated for the purposes for which the expenditure or obligations for expenditure are made. Any contract or obligation calling for an expenditure in excess of the money and credits provided and appropriated to the purposes for which such contract or obligation is created, shall be void and shall not be enforceable against the city, and the city shall refuse to recognize the validity of such contract or to pay or satisfy any such obligation. The limitations in sections 14-506 to 14-508 shall not apply to additional expenditures and obligations unavoidably made necessary in efforts to abate or control an extreme or unusual outbreak or epidemic of disease or to expenditures made imperatively necessary by the occurrence of some unforeseen or uncontrollable disaster in the city. Expenditures for the emergency purposes in this section specified shall be made only in pursuance of an ordinance duly passed reciting the conditions making necessary the further appropriation of funds, and the expenditures of such appropriation shall be limited exclusively to the purposes for which made.
Neb. Rev. Stat. §§ 14-508