The purpose of this chapter is to promote the health, safety, convenience and general welfare of the City; to encourage the most appropriate use of land throughout the City; to prevent overcrowding of the land; to conserve the value of the land and buildings; to lessen congestion in the streets; to avoid undue concentration of population; to provide adequate light and air; to facilitate adequate provisions for transportation, water, sewage, schools, parks and other public requirements; and to preserve and increase the amenities of the City, all as set forth in Massachusetts General Laws Chapter 40A, as amended.