In order that the public health, safety, morals and general welfare be furthered in an age of increasing land development and to encourage a flexibility of site design and area development, to encourage innovations in residential development so that growing demands of the population may be met and served by greater variety in design and layout of buildings and by the conservation and more effective and efficient use of open space, to encourage a more efficient use of public services, to conserve the value of the land and preservation of the property values within established residential areas, modification of the lot area and lot width may be allowed subject to compliance with subsection 26-21.5 through 26-21.9.