Iowa Code § 314.7
Officers, employees, and contractors in charge of improvement or maintenance work on any highway shall not cut down or injure any tree growing by the wayside which does not materially obstruct the highway, or tile drains, or interfere with the improvement or maintenance of the road, and which stands in front of any city lot, farmyard orchard or feed lot, or any ground reserved for any public use. Nor shall they destroy or injure reasonable ingress or egress to any property, or turn the natural drainage of the surface water to the injury of adjoining owners. It shall be their duty to use strict diligence in draining the surface water from the public road in its natural channel. To this end they may enter upon the adjoining lands for the purpose of removing from such natural channel obstructions that impede the flow of such water.
Iowa Code § 314.7