Subdrainage and levee districts may be formed of lands in main districts organized in Missouri under any existing or future law, by the owners thereof for the purpose of obtaining and providing local or more complete drainage and protection for such lands; such subdistricts to be formed and administered in the same manner as is provided by statute for the formation and administration of main districts; provided, that lands in main districts may be united with swamp or overflowed lands, either within or without other districts in the formation of new districts for the purpose of securing more complete relief or protection for land.