33 U.S.C. § 702c : US Code - Section 702C: Expenditures for construction work; conditions precedent; liability for damage from flood waters; condemnation proceedings; floodage rights

      Except when authorized by the Secretary of the Army upon the
    recommendation of the Chief of Engineers, no money appropriated
    under authority of sections 702a and 702g of this title shall be
    expended on the construction of any item of the project until the
    States or levee districts have given assurances satisfactory to the
    Secretary of the Army that they will (a) maintain all flood-control
    works after their completion, except controlling and regulating
    spillway structures, including special relief levees; maintenance
    includes normally such matters as cutting grass, removal of weeds,
    local drainage, and minor repairs of main river levees; (b) agree
    to accept land turned over to them under the provisions of section
    702d of this title; (c) provide without cost to the United States,
    all rights-of-way for levee foundations and levees on the main stem
    of the Mississippi River between Cape Girardeau, Missouri, and the
    Head of Passes.
      No liability of any kind shall attach to or rest upon the United
    States for any damage from or by floods or flood waters at any
    place: Provided, however, That if in carrying out the purposes of
    sections 702a, 702b to 702d, 702e to 702g, 702h, 702i, 702j, 702k,
    702l, 702m, and 704 of this title it shall be found that upon any
    stretch of the banks of the Mississippi River it is impracticable
    to construct levees, either because such construction is not
    economically justified or because such construction would
    unreasonably restrict the flood channel, and lands in such stretch
    of the river are subjected to overflow and damage which are not now
    overflowed or damaged by reason of the construction of levees on
    the opposite banks of the river it shall be the duty of the
    Secretary of the Army and the Chief of Engineers to institute
    proceedings on behalf of the United States Government to acquire
    either the absolute ownership of the lands so subjected to overflow
    and damage or floodage rights over such lands.