Iowa Code § 468.1: Jurisdiction to establish.

The board of supervisors of any county shall have jurisdiction, power, and authority at any regular, special, or adjourned session, to establish a drainage district or districts, and to locate and establish levees, and cause to be constructed as hereinafter provided any levee, ditch, drain, or watercourse, or settling basins in connection therewith, or to straighten, widen, deepen, or change any natural watercourse, in such county, whenever the same will be of public utility or conducive to the public health, convenience or welfare.