The terms and provisions of this subchapter shall never at any time be applicable to a drainage district organized under the general drainage laws of this state for the primary purpose of constructing levees and other flood control projects under the terms and provisions of the Flood Control Acts of Congress, approved May 15, 1928, and June 15, 1936, and any amendments thereto, and all districts organized as aforesaid are exempt from the provisions of this subchapter.