Notwithstanding any other provisions of this chapter, any nonconforming outdoor storage of materials, such as but not limited to scrap metal, used lumber or other waste, trash, rubbish or discarded material or machinery or one or more wrecked, unregistered or partially dismantled vehicles not enclosed within a building, shall, at the expiration of three years from the date of enactment of this chapter, become a prohibited and unlawful use and shall be discontinued, and all such materials shall be removed.