The open space scenic zone or zones shall include therein from time to time by amendment to the official zoning map such land as is voluntarily designated and dedicated by its owner, public or private, to be used in perpetuity for the natural scenic open space purposes hereinafter set forth. Such land includes a land or water area that is essentially unimproved or in its natural state and which possesses outstanding scenic qualities worthy of preservation. (Ord. 89-1 § 1, 1989.)