A. Any proposed alterations to a regulatory floodway require a floodplain development permit and the applicant is required to obtain a conditional letter of map revision (CLOMR) from FEMA prior to start of construction. A floodway is considered altered when there are any substantial changes to the cross sectional area or geometry, horizontal or vertical location of the streambed, or similar modifications. It is the responsibility of the applicant to have technical data prepared in a format required for a conditional letter of map revision or letter of map revision and submitted to FEMA. Submittal and processing fees for these map revisions shall be the responsibility of the applicant. Proposed alterations include:
1. Floodway encroachments that increase or decrease base flood elevations or alter floodway boundaries;
2. Fill sites to be used for the placement of proposed structures where the applicant desires to remove the site from the special flood hazard area;
3. Alteration of floodways that result in a relocation or elimination of the special flood hazard area, including the placement of culverts;
4. Subdivision or large scale development proposals requiring establishment of base flood elevations.
B. The bank full flood carrying capacity of the altered or relocated portion of the floodway cannot be diminished. Prior to issuance of a floodplain development permit, the applicant must perform an analysis meeting the requirements of subsection 15.32.180B of this chapter and submit certification by a registered professional engineer that the bank full flood carrying capacity of the floodway will not be diminished.
C. The applicant must notify adjacent communities (if applicable), the U.S. army corps of engineers, and the Idaho department of water resources stream channel alteration program prior to any alteration or relocation of a floodway. Evidence of notifications must be submitted to the floodplain administrator and to the federal emergency management agency.
D. The applicant is responsible for providing the necessary maintenance for the altered or relocated portion of the floodway so that the flood carrying capacity will not be diminished.
E. Once construction is completed the applicant must apply to FEMA for a letter of map revision for changes to the flood hazard map proposed in the CLOMR. (Ord. 3380 §7, 2010)