1. Residential Construction: New construction, substantial improvements, and development of any residential structure (including manufactured homes) shall have the lowest floor, including basement, elevated no lower than the flood protection elevation, as defined in section 9.8.02 of this chapter.
2. Non-Residential Construction: New construction, substantial improvements, and development of any commercial, industrial, or other non-residential structure shall have the lowest floor, including basement, elevated no lower than the flood protection elevation, as defined in section 9.8.02 of this chapter. Structures located in Zones A, AE, AH, AO, and A1-30 may be floodproofed to the flood protection elevation in lieu of elevation provided that all areas of the structure, together with attendant utility and sanitary facilities, below the flood protection elevation are watertight with walls substantially impermeable to the passage of water, using structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. For AH and AO Zones, the floodproofing elevation shall be in accordance with subsection 9.8.056(A)2 of this section 9.8.05. A registered professional engineer or architect shall certify that the floodproofing standards of this subsection are satisfied. Such certification shall be provided to the Floodplain Administrator as set forth in subsection 9.8.043(A)3 of this chapter, along with the operational plan and the inspection and maintenance plan.
3. Manufactured Homes:
(a) New and replacement manufactured homes shall be elevated so that the lowest floor of the manufactured home is no lower than the flood protection elevation, as defined in section 9.8.02 of this chapter.
(b) Manufactured homes shall be securely anchored to an adequately anchored foundation to resist flotation, collapse, and lateral movement, either by certified engineered foundation system, or in accordance with the most current edition of the Idaho Division of Building Safety's "Idaho Manufactured Home Installation Standard" in accordance with Idaho Code section 44-2201(2). Additionally, when the elevation would be met by an elevation of the chassis thirty six inches (36") or less above the grade at the site, the chassis shall be supported by reinforced piers or engineered foundation. When the elevation of the chassis is above thirty six inches (36") in height, an engineering certification is required.
(c) All enclosures or skirting below the lowest floor shall meet the requirements of subsections 9.8.051(A)8(a) and (A)8(b) of this section 9.8.05.
(d) An evacuation plan must be developed for evacuation of all residents of all new, substantially improved, or substantially damaged manufactured home parks or subdivisions located within flood prone areas. This plan shall be filed with and approved by the Floodplain Administrator and the local Emergency Management Coordinator.
4. Additions/Improvements:
(a) Additions and/or improvements to pre-FIRM structures when the addition and/or improvements in combination with any interior modifications to the existing structure are:
(1) Not a substantial improvement, the addition and/or improvements must be designed to minimize flood damages and must not be any more non-conforming than the existing structure; or
(2) A substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
(b) Additions to non-compliant post-FIRM structures that are a substantial improvement with no modifications to the existing structure other than a standard door in the common wall shall require only the addition to comply with the standards for new construction.
(c) Additions and/or improvements to non-compliant post-FIRM structures when the addition and/or improvements in combination with any interior modifications to the existing structure are:
(1) Not a substantial improvement, the addition and/or improvements only must comply with the standards for new construction; or
(2) A substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
5. Recreational Vehicles: Recreational vehicles shall be either:
(a) Temporary Placement:
(1) Be on site for fewer than one hundred eighty (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
(b) Permanent Placement:
6. Temporary Non-Residential Structures: Prior to the issuance of a floodplain development permit for a temporary structure, the applicant must submit to the Floodplain Administrator a plan for the removal of such structure(s) in the event of a flash flood or other type of flood warning notification. The following information shall be submitted in writing to the Floodplain Administrator for review and written approval:
(a) A specified time period for which the temporary use will be permitted. Time specified may not exceed six (6) months, renewable up to one year;
(b) The name, address, and phone number of the individual responsible for the removal of the temporary structure;
(c) The time frame prior to the event at which a structure will be removed (i.e., immediately upon flood warning notification);
(d) A copy of the contract or other suitable instrument with the entity responsible for physical removal of the structure; and
(e) Designation, accompanied by documentation, of a location outside the special flood hazard area, to which the temporary structure will be moved.
(f) Temporary structures in the floodway must provide a hydraulic and hydrology analysis along with a No-Rise Certification.
7. Accessory Structures (Appurtenant Structures): When accessory structures (sheds, detached garages, etc.) used solely for parking, and storage are to be placed within a special flood hazard area, elevation or floodproofing certifications are required for all accessory structures in accordance with subsection 9.8.043(A)3 of this chapter, and the following criteria shall be met:
(a) Accessory structures shall not be used for human habitation (including working, sleeping, living, cooking, or restroom areas);
(b) Accessory structures shall not be temperature-controlled;
(c) Accessory structures shall be designed to have low flood damage potential;
(d) Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters;
(h) Accessory structures not used solely for parking, access, and storage must be elevated per subsections (A)1 and (A)2 of this section.
An accessory structure with a footprint less than two hundred (200) square feet and is a minimal investment of seven thousand five hundred dollars ($7,500.00) or less and satisfies the criteria outlined in subsections (A)7a through (A)7g of this section is not required to provide the elevation certificate per subsection (A)2 of this section.
8. Tanks: When gas and liquid storage tanks are to be placed within a special flood hazard area, the following criteria shall be met:
(a) Underground tanks in flood hazard areas shall be anchored to prevent flotation, collapse, or lateral movement resulting from hydrodynamic and hydrostatic loads during conditions of the base flood, including the effects of buoyancy (assuming the tank is empty);
(b) Elevated above-ground tanks, in flood hazard areas shall be attached to and elevated to or above the design flood elevation on a supporting structure that is designed to prevent flotation, collapse, or lateral movement during conditions of the base flood. Tank-supporting structures shall meet the foundation requirements of the applicable flood hazard area;
(c) Not elevated above-ground tanks may be permitted in flood hazard areas provided the tanks are anchored or otherwise designed and constructed to prevent flotation, collapse or lateral movement resulting from hydrodynamic and hydrostatic loads during conditions of the design flood, including the effects of buoyancy assuming the tank is empty and the effects of flood-borne debris.
(d) Tank inlets, fill openings, outlets and vents shall be:
(1) At or above the flood protection elevation or fitted with covers designed to prevent the inflow of floodwater or outflow of the contents of the tanks during conditions of the base flood; and
(2) Anchored to prevent lateral movement resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, during conditions of the base flood.
9. Construction Of Below-Grade Crawlspace:
(a) The interior grade of a crawlspace must not be below the BFE and must not be more than two feet (2') below the exterior lowest adjacent grade (LAG).
(b) The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, must not exceed four feet (4') at any point.
(c) There must be an adequate drainage system that removes floodwaters from the interior area of the crawlspace. The enclosed area should be drained within a reasonable time after a flood event.
(d) The velocity of floodwaters at the site should not exceed five feet (5') per second for any crawlspace.
See Technical Bulletin 11 for further information.
Caution: Buildings that have below-grade crawlspaces will have higher flood insurance premiums than buildings that have the preferred crawlspace construction, with the interior elevation of the crawlspace soil at or above the base flood elevation (BFE).
10. Other Development In Regulated Floodways:
(c) Roads and watercourse crossings, including roads, bridges, culverts, low-water crossings, and similar means for vehicles or pedestrians to travel from one side of a watercourse to the other side, which encroach into regulated floodways, shall meet the limitations of section 9.8.055 of this section 9.8.05.
11. Subdivision Plats:
(a) Flood Zones:
(1) A note must be provided on the final plat documenting the current flood zone in which the property or properties are located. The boundary line must be drawn on the plat in situations where two (2) or more flood zones intersect over the property or properties being surveyed.
(2) FEMA FIRM panel(s): #160xxxxxxC, & 160xxxxxxE, etc.
FIRM effective date(s): mm/dd/year
Flood Zone(s): Zone X, Zone A, Zone AE, Zone AO, Zone AH, Zone D, etc.
Base Flood Elevation(s): AE .0 ft., etc.
Flood Zones are subject to change by FEMA & all land within a floodway or floodplain is regulated by chapter/section of the City/County Code. (Ord. 977, 1-3-2019, eff. 2-1-2019)