Chapter 28.10 — PROVISIONS FOR FLOOD HAZARD REDUCTION

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 28.10.040.

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

  1. With flood resistant materials as specified in FEMA Technical Bulletin TB 2-93, 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 floodwaters around and away from proposed structures.

• C. Elevation and Flood Proofing. (See Chapter 28.04 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 equal to or exceeding the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified. The state of California recommends that in AO zones without velocity the lowest floor be elevated above the highest adjacent grade to a height exceeding the depth number specified in feet on the FIRM by at least two feet, or elevated at least four feet above the highest adjacent grade if no depth number is specified.

     • b. In an A zone, elevated to or above the base flood elevation; said base flood elevation shall be determined by one of the methods in Section 28.08.030(B) of this title. The state of California recommends the lowest floor be elevated at least two feet above the base flood elevation, as determined by the community.

     • c. In all other zones, elevated to or above the base flood elevation. The state of California recommends the lowest floor be elevated at least two feet above the base flood elevation.

Upon the completion of the structure, the elevation of the lowest floor including

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City of Palm Desert, CA

FLOOD DAMAGE PREVENTION

§ 28.10.010

§ 28.10.030

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.

2. Nonresidential construction, new or substantial improvement, shall either be elevated to conform with subsection (C)(1) of this section or together with attendant utility and sanitary facilities:

   • a. Be flood proofed 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.

   3. 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, and must exceed the following minimum criteria:

      • a. 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; or

      • b. Be certified by a registered professional engineer or architect.

3. Manufactured homes shall also meet the standards in Section 28.10.040.

(Ord. 985 § 1, 2001)

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

  1. Infiltration of flood waters 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. 985 § 1, 2001)

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City of Palm Desert, CA § 28.10.030

PALM DESERT CODE

§ 28.10.040

• A. All preliminary subdivision proposals shall identify the special 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 subdivisions shall provide adequate drainage to reduce exposure to flood hazards. (Ord. 985 § 1, 2001)

• A. All manufactured homes that are placed or substantially improved, within Zones A1-30, AH, and AE on the community's FIRM, 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 existing 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 elevated to or above the base flood elevation (the State of California recommends at least two feet 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 that are placed or substantially improved on sites located within Zones V1-30, V, and VE on the community's FIRM will meet the requirements of subsection 28.10.040A and Section 28.10.070.

• C. 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 FIRM that are not subject to the provisions of subsection 28.10.040(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:

  1. Lowest floor of the manufactured home is at or above the base flood elevation (the state of California recommends at least two feet above the base flood elevation); or

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

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

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City of Palm Desert, CA

FLOOD DAMAGE PREVENTION

§ 28.10.040

§ 28.10.070

verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the floodplain administrator. (Ord. 985 § 1, 2001)

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

  1. Be on the site for fewer than one hundred eighty 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

2. Meet the permit requirements of Chapter 28.08 of this title and the elevation and anchoring requirements for manufactured homes in Section 28.10.040A.

(Ord. 985 § 1, 2001)

Located within areas of special flood hazard established in Section 28.06.020 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 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 Section 28.10.060(A) is satisfied, all new construction, substantial improvement, and other proposed new development shall comply with all other applicable flood hazard reduction provisions of Chapter 28.10.

• (Ord. 985 § 1, 2001)

• A. The floodplain administrator shall review permits for proposed construction of other development to determine if it is proposed within a mudslide area.

• B. Permits shall be reviewed to determine that the proposed site and improvement will be reasonably safe from mudslide hazards. Factors to be considered in making this determination include but are not limited to the:

  1. Type and quality of soils;

  2. Evidence of ground water or surface water problems;

  3. Depth and quality of any fill;

  4. Overall slope of the site; and

  5. Weight that any proposed development would impose on the slope.

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City of Palm Desert, CA § 28.10.070

PALM DESERT CODE

§ 28.10.080

• C. Within areas, which may have mudslide hazards, the floodplain administrator shall require that:

  1. A site investigation and further review be made by persons qualified in geology and soils engineering;

  2. The proposed grading, excavation, new construction, and substantial improvement be adequately designed and protected against mudslide damages;

  3. The proposed grading, excavations, new construction, and substantial improvement not aggravate the existing hazard by creating either on-site of off-site disturbances; and

4. Drainage, planting, watering, and maintenance not endanger slope stability.

(Ord. 985 § 1, 2001)

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

• B. 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.

• C. 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.

• D. Within Zone E on the FIRM, 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.

• (Ord. 985 § 1, 2001)

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City of Palm Desert, CA

FLOOD DAMAGE PREVENTION

§ 28.12.010

§ 28.12.020