A. General Standards: In all special flood hazard areas, the following provisions are required:
1. All new construction and substantial improvements shall be designed (or modified) and adequately anchored to prevent flotation, collapse, and lateral movement of the structure.
2. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
3. All new construction and substantial improvements shall be constructed by methods and practices that minimize flood damages.
4. All new and replacement electrical, heating, ventilation, plumbing, air conditioning equipment, and other service facilities shall be designed and/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, electric/gas meter panels/boxes, utility/cable boxes, hot water heaters, and electric outlets/switches.
5. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.
6. All new and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters.
7. On site waste disposal systems shall be located and constructed to avoid impairment to them or contamination from them during flooding.
8. A fully enclosed area, of new construction and substantially improved structures, which is below the lowest floor shall:
a. Be constructed entirely of flood resistant materials at least to the flood protection elevation; and
b. Include, flood openings to automatically equalize hydrostatic flood forces on walls by allowing for the entry and exit of floodwaters. To meet this requirement, the openings must either be certified by a professional engineer or architect or meet or exceed the following minimum design criteria:
(1) A minimum of two (2) flood openings on different sides of each enclosed area subject to flooding;
(2) The total net area of all flood openings must be at least one square inch for each square foot of enclosed area subject to flooding;
(3) If a building has more than one enclosed area, each enclosed area must have flood openings to allow floodwaters to automatically enter and exit;
(4) The bottom of all required flood openings shall be no higher than one foot (1') above the interior or exterior adjacent grade;
(5) Flood openings may be equipped with screens, louvers, or other coverings or devices, provided they permit the automatic flow of floodwaters in both directions; and
(6) Enclosures made of flexible skirting are not considered enclosures for regulatory purposes, and, therefore, do not require flood openings. Masonry or wood underpinning, regardless of structural status, is considered an enclosure and requires flood openings as outlined above.
9. Any alteration, repair, reconstruction, or improvements to a structure, which is in compliance with the provisions of this chapter, shall meet the requirements of "new construction" as contained in this chapter.
10. Nothing in this chapter shall prevent the repair, reconstruction, or replacement of a building or structure existing on the effective date hereof and located totally or partially within the floodway provided there is no additional encroachment below the flood protection elevation in the floodway.
11. New solid waste disposal facilities and sites, hazardous waste management facilities, salvage yards, and chemical storage facilities shall not be permitted, except by variance as specified in subsection 10-1-4E9 of this chapter.
12. All subdivision proposals and other development proposals shall be consistent with the need to minimize flood damage and determined to be reasonably safe from flooding.
13. All subdivision proposals and other development proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage.
14. All subdivision proposals and other development proposals shall have adequate drainage provided to reduce exposure to flood hazards.
15. All subdivision proposals and other development proposals shall have received all necessary permits from those governmental agencies for which approval is required by federal or state law, including section 404 of the federal water pollution control act amendments of 1972, 33 USC 1334.
16. When a structure is partially located in a special flood hazard area, the entire structure shall meet the requirements for new construction and substantial improvements.
17. When a structure is located in multiple flood hazard zones or in a flood hazard risk zone with multiple base flood elevations, the provisions for the more restrictive flood hazard risk zone and the highest base flood elevation (BFE) shall apply.
B. Specific Standards: In all special flood hazard areas where base flood elevation (BFE) data has been provided, as set forth in subsection 10-1-3B of this chapter the following provisions, in addition to the provisions of subsection A of this section, are required:
1. Residential Construction: New construction and substantial improvement 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 10-1-2 of this chapter.
2. Nonresidential Construction: New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated no lower than the flood protection elevation, as defined in section 10-1-2 of this chapter. Structures 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. The floodproofing elevation shall be in accordance with subsection F2 of this section. 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 10-1-4C3 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 10-1-2 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 subsection A8b(6) of this section.
4. 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).
(2) Recreational vehicles are not allowed to be on site in special flood hazard areas between the dates of November 30 and May 1.
b. Permanent Placement:
(1) Recreational vehicles that do not meet the limitations of temporary placement shall meet all the requirements for new construction, as set forth in subsection A of this section.
5. Temporary Nonresidential Structures: Temporary nonresidential structures are not allowed to be on site in special flood hazard areas between the dates of November 30 and May 1. (Ord. 2017-137, 2-9-2017)
6. Accessory Structures: When accessory structures (sheds, detached garages, etc.) are to be placed within a special flood hazard area the following criteria shall be met:
a. Accessory structures shall not be used for human habitation;
b. Accessory structures shall be designed to have low flood damage potential;
c. Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters;
d. Accessory structures shall be firmly anchored in accordance with the provisions of subsection A1 of this section;
e. All service facilities, such as electrical, shall be installed in accordance with the provisions of subsection A4 of this section; and
f. Flood openings to facilitate automatic equalization of hydrostatic flood forces shall be provided below flood protection elevation in conformance with the provisions of subsection A8b of this section.
An accessory structure that satisfies the criteria outlined in subsections B6a through B6f of this section is not required to meet the elevation or floodproofing standards of subsection B2 of this section. (Ord. 2018-141, 5-29-2018)
7. 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, including the effects of buoyancy;
b. Elevated aboveground 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 aboveground tanks, which do not meet the elevation requirements of subsection B2 of this section shall be permitted in flood hazard areas provided the tanks are anchored and constructed to prevent flotation, collapse or lateral movement, including the effects of buoyancy assuming the tank is empty;
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, including the effects of buoyancy.
8. Construction Of Below Grade Crawl Space:
a. The interior grade of a crawl space 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 crawl space, measured from the interior grade of the crawl space to the top of the crawl space 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 crawl space. 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 crawl space.
Caution: Buildings that have below grade crawl spaces will have higher flood insurance premiums than buildings that have the preferred crawl space construction, with the interior elevation of the crawl space soil at or above the base flood elevation (BFE).
9. Other Development In Regulated Floodways:
a. Fences that have the potential to block the passage of floodwaters, such as stockade fences and wire mesh fences, in regulated floodways shall meet the limitations of subsection E of this section.
b. Retaining walls, bulkheads, sidewalks, and driveways that involve the placement of fill in regulated floodways shall meet the limitations of subsection E of this section.
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 subsection E of this section.
C. Standards For Floodplains Without Established Base Flood Elevations: Within the special flood hazard areas designated as Zone A and established in subsection 10-1-3B of this chapter, where no base flood elevation (BFE) data has been provided by FEMA, the following provisions, in addition to the provisions of subsection A of this section, shall apply:
The BFE used in determining the flood protection elevation (FPE) shall be determined based on the following criteria:
1. When base flood elevation (BFE) data is available from other sources, all new construction and substantial improvements within such areas shall also comply with all applicable provisions of this chapter and shall be elevated or floodproofed in accordance with standards in subsections A and B of this section.
2. When floodway data is available from a Federal, State, or other source, all new construction and substantial improvements within floodway areas shall also comply with the requirements of subsections B and E of this section.
3. All subdivision, manufactured home park, and other development proposals shall provide base flood elevation (BFE) data if development is greater than five (5) acres or has more than fifty (50) lots/manufactured home sites. Such base flood elevation (BFE) data shall be adopted by reference in accordance with subsection 10-1-3B of this chapter and utilized in implementing this chapter.
4. When base flood elevation (BFE) data is not available from a Federal, State, or other source as outlined above, the lowest floor shall be elevated or floodproofed (nonresidential) to two feet (2.0') above the "highest adjacent grade (HAG)" at the building site or to the "flood protection elevation (FPE)" whichever is higher, as defined in section 10-1-2 of this chapter. All other applicable provisions of subsection B of this section shall also apply.
D. Reserved.
E. Standards For Floodways: Areas designated as floodways are located within the special flood hazard areas established in subsection 10-1-3B of this chapter. The floodways are extremely hazardous areas due to the velocity of floodwaters that have erosion potential and carry debris and potential projectiles. The following provisions, in addition to standards outlined in subsections A and B of this section, shall apply to all development within such areas:
1. No encroachments, including fill, new construction, substantial improvements, and other developments shall be permitted unless:
a. It is demonstrated that the proposed encroachment would not result in any increase in the flood levels during the occurrence of the base flood, based on hydrologic and hydraulic analyses performed in accordance with standard engineering practice and presented to the Floodplain Administrator prior to issuance of floodplain development permit.
2. If subsection E1 of this section is satisfied, all development shall comply with all applicable flood hazard reduction provisions of this chapter.
F. Standards For Areas Of Shallow Flooding: Located within the special flood hazard areas established in subsection 10-1-3B of this chapter, are areas designated as shallow flooding areas. These areas have special flood hazards associated with base flood depths of one foot (1') to three feet (3') where a clearly defined channel does not exist and where the path of flooding is unpredictable and indeterminate. In addition to subsections A and B of this section, all new construction and substantial improvements shall meet the following requirements:
1. The lowest floor shall be elevated at least as high as the depth number specified on the flood insurance rate map (FIRM), in feet, plus a freeboard of one foot (1'), above the highest adjacent grade; or at least two feet (2') above the highest adjacent grade if no depth number is specified.
2. Nonresidential structures may, in lieu of elevation, be floodproofed to the same level as required in subsection F1 of this section so that the structure, together with attendant utility and sanitary facilities, below that level shall be watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. Certification is required in accordance with subsection 10-1-4C3 of this chapter, and subsection B2 of this section.
3. Adequate drainage paths shall be provided around structures on slopes to guide floodwaters around and away from proposed structures. (Ord. 2017-137, 2-9-2017)