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1. Permitted Uses: All uses permitted in the base zone district within the this Code and as amended, are permitted in the Floodway Fringe Zone and Area of Shallow Flooding Zone to the extent that such uses are consistent with the standards within this Section.
2. Standards:
A. Uses:
(1) Except for levees, all new development shall utilize methods and practices that minimize flood damage and prevent the increase in flood damage potential to other properties or other adverse impacts 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.
(2) All new development shall utilize materials and utility equipment resistant to flood damage.
(3) All new construction and substantial improvements to structures shall be anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrostatic and hydrodynamic loads including the effects of buoyancy.
(4) All manufactured homes must likewise be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors (Reference FEMA's Protecting Manufactured Homes from Floods & Other Hazards FEMA P-85 11/2009 for additional techniques).
(5) Drainage practices shall be utilized which minimize exposure to flood hazards.
(6) Manufacture and/or storage of material which is buoyant, flammable, toxic or explosive is prohibited.
(7) River crossings shall be designed to withstand the flows and velocities of the base flood discharge and shall not impede the flows.
(8) All development and structures shall meet or exceed the requirements of Section 11-05-06 Boise River System Overlay District if applicable.
(9) Water velocities within the floodway fringe are not significantly increased so as to cause adverse effects on the site or to surrounding properties.
(10) Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.
B. Utilities:
(1) All new and replacement water supply systems shall be designed to prevent infiltration of flood waters into the systems.
(2) New and replacement wastewater disposal systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters.
(3) On-site waste disposal systems are prohibited in the Floodway Fringe Zone and Area of Shallow Flooding Zone.
(4) All new and replacement electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding to the Flood Protection Elevation. These include, but are not limited to HVAC equipment, water softener units, bath/kitchen fixtures, ductwork, electrical/gas meter panels/boxes, utility/cable boxes, hot water heaters, and electrical outlets/switches.
C. Development, Including Subdivisions And Manufactured Home Parks:
(1) All proposals shall be consistent with the need to minimize flood damage.
(2) All proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage.
(3) All proposals shall have adequate drainage to reduce exposure to flood damage.
(4) Base flood elevation data shall be provided and shown on the preliminary plat for all proposals. Such elevation data shall be certified by a licensed professional engineer or registered land surveyor. Where base flood elevation data has not been provided or is not available from another authorized source, it shall be generated for subdivision proposals and other proposed developments which contain greater than 50 lots or 5 acres (whichever is the lesser).
D. Residential Structures:
(1) New construction and substantial improvement of any residential structure (including but not limited to mobile or manufactured homes) located in the Floodway Fringe shall have the lowest floor including basements and crawl spaces, elevated two feet above the base flood elevation.
(2) New construction and substantial improvement of any residential structure located in the Area of Shallow Flooding (AO Flood Zone) shall have the lowest floor, including basements and crawl spaces, elevated one foot above the flood depth specified on the FIRM measured at highest adjacent grade, or at least two feet above highest adjacent grade when a flood depth is not identified. The height of the adjacent grade and the lowest floor including basement and/or the first floor shall be certified by a licensed professional engineer or registered land surveyor.
(3) Fully enclosed areas below the lowest floor that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or must meet or exceed the following minimum criteria:
(a) A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.
(b) The bottom of all flood openings shall be no higher than one foot above the interior or exterior adjacent grade.
(c) Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
E. Manufactured Homes:
(1) All manufactured homes that are placed or substantially improved on sites:
(a) Outside of a manufactured home park or subdivision;
(b) In a new manufactured home park or subdivision;
(c) In an expansion to an existing manufactured home park or subdivision; or
(d) In an existing manufactured home park or subdivision on which a manufactured home has incurred substantial damage as the result of a flood.
(2) All manufactured homes shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement.
(3) Manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision that are not subject to the provisions of "A" above, be elevated so that either:
(a) The lowest floor of the manufactured home is at or above the base flood elevation, or
(b) The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches in height above grade and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
F. Nonresidential Structures (Includes Accessory Structures Such As Sheds, Detached Garages, Etc.):
(1) Elevating: New construction and substantial improvement of any nonresidential structures shall meet the following:
When located in the Floodway Fringe, such structures shall have the lowest floor, including basements and crawl spaces, elevated to two feet above the base flood elevation. When located in the Area of Shallow Flooding, such structures shall have the lowest floor, including basement, elevated to the level of the base flood depth as indicated on the FIRM or at least 2 feet above highest adjacent grade if no depth number is specified.
(a) Elevations of adjacent grade and the first floor shall be certified by a licensed professional engineer or registered land surveyor to the Building Official.
(b) Nonresidential structures that are elevated, but not flood proofed, must meet the same standards for space below the first floor as described in subsection D above.
(2) Flood-Proofing: In lieu of elevating nonresidential structures as required in this Section, new construction and substantial improvement of any nonresidential structures shall meet the following:
(a) When located in the Floodway Fringe, such structures together with attendant utility and sanitary facilities shall be flood-proofed to one foot above the base flood level so the structure is watertight with walls substantially impermeable to the passage of water.
(b) When located in the Area of Shallow Flooding, such structures, together with attendant utility and sanitary facilities, shall be flood-proofed to the base flood level so the structure is watertight with walls substantially impermeable to the passage of water.
(c) Structural components shall be capable of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy.
(d) A licensed professional engineer shall certify that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this Section based on their review of the structural design, specifications and plans. Such certifications shall be provided to the Planning Director.
G. Recreational Vehicles: Recreational vehicles shall either:
(1) Be on the site for fewer than 180 consecutive days and be fully licensed and ready for highway use (a recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities, and has no permanently attached additions); or
(2) Meet the permit and elevation requirements for residential structures (subsection D above) and the anchoring requirements for manufactured homes (subsection E above). (amd. Ord. 15-20, 5-12-2020; Ord. 22-21, 5-18-2021)