(a) Each improvement authority shall have a board of trustees consisting of not more than five members that are qualified electors residing in the area serviced by the authority.

(b) When the authority is composed of an incorporated city or town, the trustees shall be appointed by the governing body of the city or town. When the authority is composed in whole or in part of the inhabitants of an unincorporated area, the governing body of the county in which the area is composed appoints the trustees. In the event the unincorporated area is composed of parts of different counties, the Governor of the state shall appoint the board. All vacancies on the board shall be filled by the proper authority designated in this section. The first appointment of the members of the board shall be made not later than 30 days after the improvement authority becomes an incorporation as provided for in this chapter.

(c) The term of the office of the members of the board shall be one, two, and three years respectively dating from January 1 of the year in which the appointments are made. Thereafter the terms of office of the members are for three years. Members shall hold office until their successors are appointed and qualify. An appointment to fill a vacancy shall be for the unexpired term.

(d) The appointing authority may remove any member within the term for which he or she shall have been appointed, after giving a copy of the charges against the member and an opportunity to be heard in his or her defense. The action of the appointing authority shall be final and nonreviewable.