$272,000,000 is authorized to be appropriated for the carrying out of the modified adopted project, and all unexpended balances of appropriations heretofore made for the prosecution of said flood-control project are made available for the purposes of sections 642a, 702a-1, 702a-2 to 702a-12, 702g-1, 702j-1, 702j-2, 702k-1, and 702k-2 of this title.