Flood control works shall be allowed within floodways subject to the issuance of a permit by the floodplain administrator with the following conditions:

A. Levees and floodwalls are permitted if:

1. The proposed levee or floodwall is designed and constructed to safely convey a one-hundred-year flood; and

2. The cumulative effect of the levee or floodwall combined with allowable floodway fringe encroachments does not increase the unobstructed base flood elevation more than 0.5 foot. The floodplain administrator may establish either a lower or higher permissible increase in the base flood elevation for individual levee projects only with concurrence from the Montana Department of Natural Resources and Conservation and the Federal Emergency Management Agency based upon consideration of the following criteria:

a. The estimated cumulative effect of any anticipated future permissible uses, and

b. The type and amount of existing flood-prone development in the affected area;

3. The proposed levee or floodwall, except those to protect agricultural land, are constructed at least three feet higher than the base flood elevation.

B. Riprap, except that which is hand-placed, if:

1. The riprap is designed to withstand a one-hundred-year flood;

2. The riprap does not increase the base flood elevation; and

3. The riprap will not increase erosion upstream, downstream, or adjacent to the riprap site.

C. Channelization projects if they do not significantly increase the magnitude, velocity, or base flood elevation in the proximity of the project.

D. Dams; provided, that:

1. They are designed and constructed in accordance with the Montana Dam Safety Act and applicable safety standards; and

2. They will not increase flood hazards downstream, either through operational procedures or improper hydrologic/hydraulic design. (Ord. 576 § 6(B)(3), 1994)