The superintendent of social services, who shall be head of the department of social services, shall be chosen from a list of eligibles furnished by the State Department of Social Services. Such person shall exercise the powers conferred and perform the duties imposed by general law upon the county board of social services, not inconsistent herewith. Such person shall also perform such other duties as the board imposes upon him. The board shall select at least five and not more than 11 qualified county citizens, one of whom may be a member of the urban county board of supervisors, who shall constitute the county board of social services. The board shall designate an additional seat on the board for a qualified citizen of each city to which the county is contractually obligated to provide social services. Such board shall advise and cooperate with the department of social services and may adopt necessary rules and regulations not in conflict with law concerning such department. As provided for in Chapters 2 (§ 63.2-200 et seq.) and 3 (§ 63.2-300 et seq.) of Title 63.2, the urban county board of supervisors in its discretion may designate either the superintendent of social services or the above-mentioned county board of social services as the local board. If the urban county board of supervisors designates the superintendent of social services as constituting the local board, the county board of social services shall serve in an advisory capacity to such officer with respect to the duties and functions imposed upon him by law.