Iowa Code § 464B.23: Protection of banks.

Where the water backed up by any dam belonging to any mill or machinery is about to break through or over the banks of the stream or raceway, or to wash a channel, so as to turn the water of such stream or raceway, or any part thereof, out of its ordinary channel, whereby such mill or machinery will be materially injured or affected, the owner or occupant of such mill or machinery, if that person does not own such banks or the land lying contiguous thereto, may, if necessary, enter thereon and erect and keep in repair such embankments and other works as may be necessary to prevent such water from breaking through or over the banks, or washing a channel as aforesaid; such owner or occupier committing thereon no unnecessary waste or damage, and being liable to pay all damages which the owner of the lands may actually sustain by reason thereof.