Iowa Code § 468.6: Number of petitioners required.

Two or more owners of lands named in the petition described in section 468.8, may file in the office of the county auditor a petition for the establishment of a levee or drainage district, including a district which involves only the straightening of a creek or river. If the district described in the petition is a subdistrict, one or more owners of land affected by the proposed improvement may petition for such district.