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1. Permitted Uses: All uses permitted by the base zone district within this Code, and as amended are permitted in Floodway Zones to the extent that the uses are consistent with the standards of this Section.
2. Standards:
A. No new development shall be permitted including fill, new construction, substantial improvements or other development, unless:
(1) It is public infrastructure, including but not limited to bridges, roadways, sewer and water lines, and
(2) It has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels within the community during the occurrence of the base flood discharge.
B. All new development, new construction and substantial improvements shall comply with the applicable standards for uses in the Floodway Fringe.
C. Existing structures in the Floodway Zone which are displaced by floodwater shall not be reconstructed.
D. No alteration or relocation of a water course shall be permitted which would diminish the flood carrying capacity of the water course, or which would result in the flooding of lands which are not subject to flooding prior to such alteration or relocation of the water course, or which will result in adverse effects on other properties including but not limited to, bank erosion resulting from higher velocities, increased heights of floodwaters, extended flood duration, or alterations that may promote channel blockage.
E. Uses on parcels which include any portion of a floodway shall provide for channel stabilization, bank stabilization, or a setback from the edge of the floodway sufficient to protect the use from flood related erosion. Such measures shall be reviewed by a licensed professional engineer for effectiveness for the flood flow and velocity conditions anticipated at the site.
F. Check dams shall be designed and reviewed by a licensed professional engineer, and reviewed and approved by the Boise City Engineer to ensure the safety of persons and property which could be affected by the construction of the check dam.
G. In areas where a regulatory floodway has not been designated, no new construction, substantial improvements, other development (Including fill) shall be permitted within zones A1-30 and AE on the community's FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot at any point within the community.
3. Prohibited Uses:
A. New construction or substantial improvements of residential and non- residential structures, including both principal and accessory use structures, except as provided in 11-08-02.2.
B. Manufacture and storage of materials which are buoyant, flammable, toxic or explosive, or which may present a hazard to public health or safety in time of flooding.
C. Standards for Sand and Gravel Extraction - Material stockpiles and permanently installed structures shall not be located within the floodway.
4. Relocating The Floodway (Line):
A. All proposals to redefine the floodway boundary lines require a resolution from the Boise City Council to adopt the amendments to the Flood Insurance Rate Map, and the Flood Insurance Study. The procedure shall include a review by the U.S. Army Corps of Engineers, the Federal Emergency Management Agency (LOMC Process), the Boise City Department of Public Works, and the Boise City Planning and Development Services Department, prior to submittal to the City Council.
B. The Floodway Boundary Line may be relocated due to refinements of the floodway calculations based upon new information concerning the existing conditions.
C. The floodway boundary line may not be relocated through physical alterations to the lands in the floodplain. (amd. Ord. 15-20, 5-12-2020)