Iowa Admin. Code r. 567-75.4

Current through Register Vol. 47, No. 11, December 11, 2024

Rule 567-75.4 - Establishment of a floodway

Regulations established by department flood plain management order or by approved local ordinances shall provide for a floodway: An area of the flood plain which must be reserved for the conveyance of flood flows so that flood heights and velocities will not be substantially increased by future encroachment on the flood plain. Delineation of the encroachment limits defining the outer limits of the floodway must conform to the following criteria insofar as possible.

(1)Increase in water surface elevation. The increase in the water surface elevation of Q100 which would result from confining flood flows to the floodway shall not exceed one foot.

(2)Equal and opposite conveyance. The concept of equal and opposite conveyance as defined in 567-Chapter 70 shall be used to locate encroachment limits.

(3)Protection of existing development. To the extent feasible, encroachment limits shall be located as follows:

a. To avoid the need to seek removal of a lawful existing structure in order to safely convey Q100;

b. To minimize any increase in the level of Q100 in an area where such increase would adversely affect an existing lawful structure;

c. To avoid the need to place an existing lawful structure in a delineated floodway if the placement would result in additional restrictions on improvements or reconstruction or replacement of the structure.

(4)When acquisition of property interest required. Where protection of an existing structure necessitates prohibition of development in an area which could otherwise be developed under the criteria in 75.4(1) and 75.4(2), the department or local governmental designee may require that the owners of land benefited by the application of criteria in this subrule acquire property interests as needed to provide an adequate alternative floodway.

Iowa Admin. Code r. 567-75.4