The area of operation of a regional housing authority shall include, except as otherwise provided in this chapter and Chapter 11, all of the counties for which such regional housing authority is created and established. But such area of operation shall not include any portion of any county which lies within the territorial boundaries of any city until a resolution is adopted by the council of the city and also by the housing authority of the city if it shall have been theretofore established declaring, as provided in § 31-3-400, that there is need for the regional housing authority to exercise its powers within such city.