In any case where the United States Government, or any agency thereof, under the authority of an act of Congress has heretofore commenced or finished, or shall hereafter commence or finish, any work on or construction of a retarding dam, channel improvement or other flood control project in relation to any river, stream or creek in this Commonwealth, and the authorized representatives of the United States deem it necessary for the successful operation of said flood control project and for the safety of life and preservation of property to secure from the Commonwealth or any political subdivision thereof certain easements and rights in or relative to the highways, roads, streets and bridges thereof and the land bordering the same over which such governmental units may have control, the Commonwealth and the various political subdivisions thereof are hereby authorized to grant to the United States such easements and rights and to enter into agreements therewith as hereinafter provided.