The board shall cause to be removed from the ditches, drains, and laterals of any district any obstructions which interfere with the flow of the water, including trees, hedges, or shrubbery and the roots thereof, and may cause any tile drain so obstructed to be relaid in concrete or any other adequate protection, such work to be paid for from the drainage funds of the district.
Iowa Code § 468.138
89 Acts, ch 126, §2