1. The regulations shall be made in accordance with a comprehensive plan and designed to preserve the availability of agricultural land; to consider the protection of soil from wind and water erosion; to encourage efficient urban development patterns; to lessen congestion in the street or highway; to secure safety from fire, flood, panic, and other dangers; to protect health and the general welfare; to provide adequate light and air; to prevent the overcrowding of land; to avoid undue concentration of population; to promote the conservation of energy resources; to promote reasonable access to solar energy; and to facilitate the adequate provision of transportation, water, sewerage, schools, parks, and other public requirements. However, provisions of this section relating to the objectives of energy conservation and access to solar energy shall not be construed as voiding any zoning regulation existing on July 1, 1981, or to require zoning in a county that did not have zoning prior to July 1, 1981.
 2. The regulations shall be made with reasonable consideration, among other things, as to the character of the area of the district and the peculiar suitability of such area for particular uses, and with a view to conserving the value of buildings and encouraging the most appropriate use of land throughout such county.
 3. The regulations and comprehensive plan shall be made with consideration of the smart planning principles under section 18B.1 and may include the information specified in section 18B.2, subsection 2.
 4. a. A comprehensive plan recommended for adoption by the zoning commission established under section 335.8, may be adopted by the board of supervisors. The board of supervisors may amend a proposed comprehensive plan prior to adoption. The board of supervisors shall publish notice of the meeting at which the comprehensive plan will be considered for adoption. The notice shall be published as provided in section 331.305.

 b. Following its adoption, copies of the comprehensive plan shall be sent or made available to neighboring counties, cities within the county, the council of governments or regional planning commission where the county is located, and public libraries within the county.
 c. Following its adoption, a comprehensive plan may be amended by the board of supervisors at any time.