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.