Iowa Code § 468.231
When establishing a board of county drainage administrators, the board of supervisors shall divide the county, along township lines, into three drainage administrator areas of approximately equal territory. The board of county drainage administrators shall consist of one resident freeholder appointed by the county board of supervisors from each area, and at least two of the administrators shall be agricultural landowners. The members first appointed shall hold office for terms of one, two, and three years respectively, as indicated and fixed by the county board of supervisors. Thereafter, succeeding members shall be appointed for a term of three years, except that vacancies occurring otherwise than by expiration of a term shall be filled by appointment for the unexpired term. Any member of the board of county drainage administrators who shall cease to have any of the qualifications prescribed by this section shall thereupon be disqualified as a member of the board and the office shall be deemed vacant. Members of the board of county drainage administrators may be removed by the county board of supervisors for cause, but every such removal shall be by written order which shall be filed with the county auditor.
Iowa Code § 468.231
89 Acts, ch 126, §2