Iowa Code § 468.315: Authority to include city.

A county board of supervisors has the same power to establish a drainage or levee district that includes the whole or any part of a city as the county board does to establish a district located wholly outside a city, including providing for the assessment of damages and benefits within a city. However, a county board of supervisors shall not do any of the following:

1. Establish a drainage or levee district located wholly within the corporate limits of a city, unless the city consents by resolution adopted by its city council.

2. Establish a district for sanitary sewer purposes.