The lawful use of land or a building existing at the effective date hereof may be continued, subject to the provisions of this title, although such use does not conform with the provisions hereof. A nonconforming use may not be changed to another nonconforming use. Whenever a nonconforming use of land or a building has been changed to a conforming use, such shall not thereafter be changed back to a nonconforming use. This section, together with other provisions of this chapter, shall also apply to a use based upon a variance granted under prior zoning ordinances. (Ord. 349, 1-24-2006)