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Chapter 29 — FLOODPLAIN MANAGEMENT

Article IV — Provisions for Flood Hazard Reduction

Alturas Municipal Code · 2026-09 edition · updated 2026-10-01 · Alturas

Sec. 29-16. - Standards of construction.

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

(a)

Anchoring.

(1)

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.

(2)

All manufactured homes shall meet the anchoring standards of section 29-19.

(b)

Construction Materials and Methods. All new construction and substantial improvement shall be constructed:

(1)

With materials and utility equipment resistant to flood damage;

(2)

Using methods and practices that minimize flood damage;

(3)

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; and if

(4)

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

(c)

Elevation and Floodproofing. (See section 29-5, definitions, for "basement," "lowest floor," "new construction," "substantial damage", and "substantial improvement.")

(1)

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

a.

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

b.

In an A zone, elevated at least one foot above the base flood elevation, as determined by this community.

c.

In zones AE, AH, and A1-30, elevated at least the base flood elevation, as determined by this community.

Upon the completion of the structure, 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 by the floodplain administrator.

(2)

Nonresidential construction shall either be elevated to conform with subsection (c)(1) of this section or together with attendant utility and sanitary facilities:

a.

Be floodproofed below the elevation recommended under subsection (c)(1) of this section so that the structure is watertight with walls substantially impermeable to the passage of water;

b.

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

c.

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

(4)

All new construction and substantial improvements 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 must exceed the following minimum criteria:

a.

Be certified by a registered professional engineer or architect; or

b.

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.

(5)

Manufactured homes shall also meet the standards in section 29-19.

(Ord. No. 477, § 2, 12-9-2008)

Exceptions & meaning →

Sec. 29-17. - Standards for utilities.

(a)

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

(1)

Infiltration of floodwaters into the systems, and

(2)

Discharge from the systems into floodwaters.

(b)

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

(Ord. No. 477, § 2, 12-9-2008)

Exceptions & meaning →

Sec. 29-18. - Standards for subdivisions.

(a)

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

(b)

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.

(c)

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

(d)

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

(e)

All new subdivision proposals and other proposed developments (including proposals for manufactured home parks and subdivisions) greater than fifty lots or five acres, whichever is the lesser, include within such proposals base flood elevation data.

(f)

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

(Ord. No. 477, § 2, 12-9-2008)

Exceptions & meaning →

Sec. 29-19. - Standard for manufactured homes.

(a)

All manufactured homes that are placed or substantially improved, within zones A-30, AH, and AE on the community's flood insurance rate map, on sites located:

(1)

Outside of a manufactured home park or subdivision;

(2)

In a new manufactured home park or subdivision;

(3)

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

(4)

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 at least one foot above the base flood elevation and be securely fastened to an adequately anchored foundation system to resist flotation collapse and lateral movement.

(b)

All manufactured homes to be placed or substantially improved on site in an existing manufactured home park or subdivision within zones A1-30, AH, AE, on the community's flood insurance rate map that are not subject to the provisions of subsection (a) of this section will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and elevated so that either the:

(1)

Lowest floor of the manufactured home is at the least one foot above the base flood elevation; or

(2)

Manufactured home chassis is supported by reinforced piers or other foundation elements of at lest equivalent strength that are no less than thirty-six inches in height above grade.

(Ord. No. 477, § 2, 12-9-2008)

Exceptions & meaning →

Sec. 29-20. - Standards for recreational vehicles.

(a)

All recreational vehicles placed on sites within zones A1-30, AH, or AE on the community's flood insurance rate map will either:

(1)

Be on the site for fewer than one hundred eighty consecutive days;

(2)

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

(3)

Meet the permit requirements of article III of this chapter and the elevation and anchoring requirements for manufactured homes in subsection 29-19(a).

(Ord. No. 477, § 2, 12-9-2008)

Exceptions & meaning →

Sec. 29-21. - Floodways.

Located within areas of special flood hazard established in section 29-7 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:

(a)

Prohibit encroachments, including fill, new construction, substantial improvement, and other new development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in (the base) flood elevation during the occurrence of the base flood discharge.

(b)

If subsection (a) of this section is satisfied, all new construction, substantial improvement, and other proposed new development shall comply with all other applicable flood hazard reduction provisions of this article.

(Ord. No. 477, § 2, 12-9-2008)

Exceptions & meaning →

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