Division 4.3: Flood Hazard Reduction Standards

In all areas of special flood hazards the following standards are required:

No rise of BFE in the floodplain. No new construction, substantial improvements, or other development (including cut and/or fill) shall be permitted within zones A and AO-A30 on the community's flood insurance rate maps unless it is first demonstrated by engineering data submitted by the applicant's engineer in accordance with the various requirements and procedures set forth in this division that the cumulative effect of the proposed development will not increase the water surface elevation of the base flood at any point within the community, or immediately adjacent to its territory.

Compensatory storage. Whenever any portion of a floodplain is authorized for use, the space occupied by the authorized fill or structure below the base flood elevation shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the base flood elevation. All such excavations shall be constructed to drain freely to the watercourse.

New development or substantial improvement in the 100-year floodplain may not increase erosive water velocity on site or off site.

Anchoring.

All new construction and substantial improvements shall be adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

All manufactured homes shall meet the anchoring standards of Section 4.3.4.

Construction materials and methods. All new construction and substantial improvement shall be constructed:

With flood resistant materials as specified in FEMA Technical Bulletin TB 2-93, or subsequent replacement Bulletin, and utility equipment resistant to flood damage;

Using methods and practices that minimize flood damage;

With electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding, located one foot above the base flood elevation; and

If within zones AH or AO, so that there are adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.

Elevation and Floodproofing. (See Article 9 for "basement," "lowest floor," "new construction," "substantial damage" and "substantial improvement.")

Residential construction, new or substantial improvement, shall have the lowest floor, including basement:

In an AO zone, elevated above the highest adjacent grade to a height equal to or exceeding one foot above the depth number specified in feet on the FIRM, or elevated at least one foot above the highest adjacent grade if no depth number is specified.

In an A zone, elevated to or above one foot above the base flood elevation; said base flood elevation shall be determined by one of the methods in Section 4.2.4.B of this article.

In all other zones, elevated to or above one foot above the base flood elevation.

Upon the completion of construction of the foundation, and prior to any additional construction, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the floodplain administrator.

Nonresidential construction, new or substantial improvement, shall either be elevated to conform with Subsection E or together with attendant utility and sanitary facilities:

Be floodproofed below the elevation recommended under Subsection F.1 so that the structure is watertight with walls substantially impermeable to the passage of water;

Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and

Be certified by a registered professional engineer or architect that the standards of this Subsection 2 are satisfied. Such certification shall be provided to the floodplain administrator.

All new construction and substantial improvement with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for parking of vehicles, building access or storage, and which are subject to flooding, shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwater. Designs for meeting this requirement shall follow the guidelines in FEMA Technical Bulletins TB 1-93 and TB 7-93, or subsequent replacement bulletins, and must exceed the following minimum criteria:

Have 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. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater; and

Be certified by a registered professional engineer or architect.

Manufactured homes shall also meet the standards in Section 4.3.4.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.2 Standards for utilities

All new and replacement water supply and sanitary sewage systems shall be designed and placed to minimize or eliminate:

Infiltration of floodwaters into the systems; and

Discharge from the systems into floodwaters.

On-site waste disposal systems shall be located to avoid impairment to them, or contamination from them during flooding.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.3 Standards for subdivisions

All preliminary subdivision proposals shall identify the special flood hazard area and the elevation of the base flood.

All subdivision plans will provide the elevation of proposed structure(s) and pad(s). If the site is filled above the base flood elevation, the lowest floor and pad elevations shall be certified by a registered professional engineer or surveyor and provided to the floodplain administrator.

All subdivision proposals shall be consistent with the need to minimize flood damage.

All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.

All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

All subdivision plans shall identify at least one surveyed, permanently installed monument. Additional monuments will be required for every 100 acres on the site described for development.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.4 Standards for manufactured homes

All manufactured homes that are placed or substantially improved, within zones A1-30, AH, and AE on the community's Flood Insurance Rate Map, on sites located:

Outside of a manufactured home park or subdivision;

In a new manufactured home park or subdivision;

In an expansion to an existing manufactured home park or subdivision; or

In an existing manufactured home park or subdivision on a site upon which a manufactured home has incurred "substantial damage" as the result of a flood shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above two feet above the base flood elevation and be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.

All manufactured homes that are placed or substantially improved on sites located within zones V1-30, V, and VE on the community's Flood Insurance Rate Map will meet the requirements of Subsection A.

All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within zones A1-30, AH, AE, V1-30, V, and VE on the community's Flood Insurance Rate Map that are not subject to the provisions of Subsection A will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and be elevated so that either the:

Lowest floor of the manufactured home is at or above two feet above the base flood elevation; or

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.

All manufactured homes to be placed within zone A on a community's FHBM or FIRM shall be installed using methods and practices which minimize flood damage. For the purposes of this requirement, manufactured homes must be elevated and anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.5 Standards for recreational vehicles

All recreational vehicles placed on sites within zones A1-30, AH, and AE on the community's Flood Insurance Rate Map will either:

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 security devices, and has no permanently attached additions; or

Meet the permit requirements of Division 4.2 and the elevation and anchoring requirements for manufactured homes in Section 4.3.4.A.

Recreation vehicles placed on sites within zones V1-30, V, and VE on the community's Flood Insurance Rate Map will meet the requirements of Subsection A.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.6 Floodways

Located within areas of special flood hazard established in Section 4.1.2.7 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters, which carry debris, potential projectiles, and erosion potential, the following provisions apply:

Encroachments, including fill, new construction, substantial improvement, and other new development are prohibited, unless 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.

If Subsection A above is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of Division 9.3.

Under the provisions of 44 CFR chapter 1, section 65.12, of the National Flood Insurance Program regulations, a community may permit encroachments within the adopted regulatory floodway that would result in an increase in base flood elevations, provided that the community first completes all of the provisions required by section 65.12 of the National Flood Insurance Program regulations.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.7 Flood-related erosion-prone area

The floodplain administrator shall require permits for proposed construction and other development within all flood-related erosion-prone areas as known to the community.

Permit applications shall be reviewed to determine whether the proposed site alterations and improvements will be reasonably safe from flood-related erosion and will not cause flood-related erosion hazards or otherwise aggravate the existing hazard. If a proposed improvement is found to be in the path of flood-related erosion or would increase the erosion hazard, such improvement shall be relocated or adequate protective measures shall be taken to avoid aggravating the existing erosion hazard.

Within zone E on the Flood Insurance Rate Map, a setback is required for all new development from the ocean, lake, bay, riverfront or other body of water to create a safety buffer consisting of a natural vegetative or contour strip. This buffer shall be designated according to the flood-related erosion hazard and erosion rate, in relation to the anticipated useful life of structures, and depending upon the geologic, hydrologic, topographic, and climatic characteristics of the land. The buffer may be used for suitable open space purposes, such as for agricultural, forestry, outdoor recreation and wildlife habitat areas, and for other activities using temporary and portable structures only.

(Ordinance 2025-O-650 adopted 1/9/2025)

§ 4.3.8 Standards for areas of shallow flooding (AO/AH Zones)

Located within the areas of special flood hazard established in Section 4.1.2.7, are areas designated as shallow flooding. These areas have special flood hazards associated with flood depths of 1 to 3 feet where a clearly defined channel does not exist, where the path of flooding is unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow; therefore, the following provisions apply:

All new construction and substantial improvements of residential structures have the lowest floor (including basement) elevated to or above the base flood elevation or the highest adjacent grade at least as high as the depth number specified in feet on the community's firm (at least 2 feet if no depth number is specified).

All new construction and substantial improvements of nonresidential structures:

Have the lowest floor (including basement) elevated to or above the base flood elevation or the highest adjacent grade at least as high as the depth number specified in feet on the community's FIRM (at least 2 feet if no depth number is specified); or

Together with attendant utility and sanitary facilities be designed so that below the base specified flood depth in an AO zone, or below the base flood elevation in an AH zone, level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads of effects of buoyancy.

A registered professional engineer or architect shall submit a certification to the floodplain administrator that the standards of this section, as proposed in Section 4.3.1 are satisfied.

Require within zones AH or AO adequate drainage paths around structures on slopes, to guide floodwaters around and away from proposed structures.

(Ordinance 2025-O-650 adopted 1/9/2025)