Iowa Code § 468.124: New district including old district.

If any levee or drainage district or improvement established either by legal proceedings or by private parties shall be insufficient to properly drain all of the lands tributary thereto, the board upon petition as for the establishment of an original levee or drainage district, shall have power to establish a new district covering and including such old district or improvement together with any additional lands deemed necessary. All outstanding indebtedness of the old levee or drainage district shall be assessed only against the lands included therein.