The purpose of the provisions of this title shall be to promote the public health, safety, morals, convenience and general welfare, to lessen traffic congestion in the streets, to provide light and air for all buildings, to avoid understandable concentrations of population, to prevent overcrowding of land and to facilitate adequate provision of transportation, water, sewage, schools, parks and other public requirements, and to provide the economic and social advantages gained from a comprehensively planned use of land resources. (1973 Code § 17.04.020)