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
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.