Section 10 of the Rivers and Harbors Act of 1899
33 U.S.C. 403
The U.S. Army Corps of Engineers is the federal agency that regulates wetlands disturbing activities. It does so under the Clean Water Act, Section 401(33U.S.C 1341) or 404 (33 U.S.C 1344), and the Rivers and Harbors Act, Section 10 (33 U.S.C 403). A brief summary can be found HERE.
Original Language: "That the creation of any obstruction not affirmatively authorized by Congress, to the navigable capacity of any of the waters of the United States is hereby prohibited; and it shall not be lawful to build or commence the building of any wharf, pier, dolphin, boom, weir, breakwater, bulkhead, jetty, or other structures in any port, roadstead, haven, harbor, canal, navigable river, or other water of the United States, outside established harbor lines, or where no harbor lines have been established, except on plans recommended by the Chief of Engineers and authorized by the Secretary of War; and it shall not be lawful to excavate or fill, or in any manner to alter or modify the course, location, condition, or capacity of, any port, roadstead, haven, harbor, canal, lake, harbor of refuge, or inclosure within the limits of any breakwater, or of the channel of any navigable water of the United States, unless the work has been recommended by the Chief of Engineers and authorized by the Secretary of War prior to beginning the same."