Mo. Rev. Stat. § 245.190
Where the works set out in the plan for reclamation of any levee district is found insufficient to reclaim in whole or in part any or all of the land and other property of the district the board of supervisors shall have the right to formulate new or amended plans containing new levees or other works, or providing for the enlargement of existing levees or other works, and additional assessments may be made in conformity with the provisions of section 245.180, the same to be made in proportion to the increased benefits accruing to the lands and other property because of the additional works. If it should be found at any time that the amount of total tax levied under the provisions of section 245.180 is insufficient to pay cost of works set out in the plan for reclamation or additional work done under the provisions of this section, the board of supervisors may make an additional levy to provide funds to complete the work; provided, the total of all levies of such tax does not exceed the total amount of benefits assessed.
§ 245.190, RSMo