Article 5 — Provisions for Flood Hazard Reduction

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

(a) Anchoring. All new construction and substantial improvements of structures, including manufactured homes, 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.

(b) Construction materials and methods. All new construction and substantial improvements of structures, including manufactured homes, shall be constructed:

(1) With flood resistant materials, and utility equipment resistant to flood damage for areas below the base flood elevation;

• (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

(4) Within Zones AH or AO, so that there are adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures.

• (c) Elevation and floodproofing.

• (1) Residential construction, new or substantial improvement, shall have the lowest floor, including basement:

• (i) In AE, AH, A1-30 Zones, elevated at least one (1) foot above the base flood elevation.

(ii) 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 (1) foot, or elevated at least three (3) feet above the highest adjacent grade if no depth number is specified.

(iii) In an A Zone, without BFE’s specified on the FIRM [unnumbered A zone], elevated at least one (1) foot above the base flood elevation, as determined under Section 8-4.402(c).

Prior to the framing of walls and/or floors of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or licensed land surveyor, and verified by the County Building Official or their designee, to be properly elevated. Such certification or verification shall be provided to the Floodplain Administrator.

(2) Nonresidential construction. All new construction or substantial improvement of nonresidential structures shall either be elevated to conform with Section 8-4.501(c)(1), or:

(i) Be floodproofed, together with attendant utility and sanitary facilities, below the elevation recommended under Section 8-4.501(c)(1) so that the structure is watertight with walls substantially impermeable to the passage of water;

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

(iii) Be certified by a registered civil engineer or architect that the standards of Section 8-4.501(c)(2)(i) & (ii) are satisfied. Such certifications shall be provided to the Floodplain Administrator.

(3) Flood openings. 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 meet or exceed the following minimum criteria;

• (i) For non-engineered openings:

• a. Have a minimum of two (2) openings on different sides having a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding;

• b. The bottom of all openings shall be no higher than one (1) foot above grade;

• c. 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

• d. Buildings with more than one (1) enclosed area must have openings on exterior walls for each area to allow flood water to directly enter; or

• (ii) Be certified by a registered civil engineer or architect.

• (4) Manufactured homes. See Section 8-4.504.

• (5) Garages and low cost accessory structures.

• (i) Attached garages.

a. A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry of flood waters. See Section 8-4.501(c)(3). Areas of the garage below the BFE must be constructed with flood resistant materials. See Section 8-4.501(b).

b. A garage attached to a nonresidential structure must meet the above requirements or be dry floodproofed. For guidance on below grade parking areas, see FEMA Technical Bulletin TB-6.

• (ii) Detached garages and accessory structures.

a. “Accessory structures” used solely for parking (two (2) car detached garages or smaller) or limited storage (small, low-cost sheds), as defined in Section 8-4.201, may be constructed such that its floor is below the base flood elevation (BFE), provided the structure is designed and constructed in accordance with the following requirements:

1. Use of the accessory structure must be limited to parking or limited storage;

2. The portions of the accessory structure located below the BFE must be built using flood-resistant materials;

3. The accessory structure must be adequately anchored to prevent flotation, collapse and lateral movement;

4. Any mechanical and utility equipment in the accessory structure must be elevated or floodproofed to or above the BFE;

5. The accessory structure must comply with floodplain encroachment provisions in Section 8-4.506; and

6. The accessory structure must be designed to allow for the automatic entry of flood waters in accordance with Section 8-4.501(c)(3).

b. Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in Section 8-4.501.

• (Ord. 1445, eff. August 14, 2014; as amended by Ord. 1500, eff. July 26, 2018)

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

• (a) infiltration of flood waters into the systems; and

• (b) discharge from the systems into flood waters.

• (Ord. 1445, eff. August 14, 2014; as amended by Ord. 1500, eff. July 26, 2018)

(a) All preliminary subdivision proposals and other proposed development, including proposals for manufactured home parks and subdivisions, greater than fifty (50) lots or five (5) acres, whichever is the lesser, shall:

• (1) Identify the Special Flood Hazard Areas (SFHA) and the Base Flood Elevation (BFE).

• (2) Identify the elevations of lowest floors all proposed structures and pads on the final plans.

(3) If the site is filled above the base flood elevation, the following as-built information for each structure shall be certified by a registered civil engineer or licensed land surveyor and provided as part of an application for a Letter of Map Revision based on Fill (LOMR-F) to the Floodplain Administrator:

• (i) Lowest floor elevation.

• (ii) Pad elevation.

• (iii) Lowest adjacent grade.

• (b) All subdivision proposals and other proposed development shall be consistent with the need to minimize flood damage.

• (c) All subdivision proposals and other proposed development shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.

(d) All subdivisions and other proposed development shall provide adequate drainage to reduce exposure to flood hazards.

• (Ord. 1445, eff. August 14, 2014; as amended by Ord. 1500, eff. July 26, 2018)

(a) All manufactured homes that are placed or substantially improved, within special flood hazard areas, 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

• (i) Within Zones A1-30, AH, and AE on the community's Flood Insurance Rate Map, be elevated on a

permanent foundation such that the lowest floor of the manufactured home is elevated to at least one (1) foot above the base flood elevation and shall 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 sites in an existing manufactured home park or subdivision within Zones A1-30, AH, and AE on the community's Flood Insurance Rate Map that are not subject to the provisions of Section 8-4.504(a) shall be securely fastened to an adequately anchored foundation system to resist floatation collapse, and lateral movement, and shall be elevated so that either the:

• (1) Lowest floor of the manufactured home is at least one (1) foot 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 (36) 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 civil engineer or licensed land surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator.

(Ord. 1445, eff. August 14, 2014; as amended by Ord. 1500, eff. July 26, 2018)

All recreational vehicles placed on sites within special flood hazard areas will either:

(a) Be on the site for fewer than one hundred eighty (180) consecutive days, or

(b) 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

(c) Meet the permit requirements of Articles 4 and 5 of this chapter and the elevation and anchoring requirements for manufactured homes in Section 8-4.504(a).

(Ord. 1445, eff. August 14, 2014; as amended by Ord. 1500, eff. July 26, 2018)

Located within areas of special flood hazard established in Section 8-4.302 are areas designated as floodways. Since floodways are an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

(a) Until a regulatory floodway is adopted, no new construction, substantial development, or other development (including fill) shall be permitted within Zones A1-30 and AE, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other development, will not increase the water surface elevation of the base flood more than one (1) foot at any point within the County of Yolo.

(b) Within an adopted regulatory floodway, the County of Yolo shall prohibit encroachments, including fill, new construction, substantial improvements, 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.

(c) If subsections (a) and (b) are satisfied, all new construction, substantial improvements, and other proposed new development shall comply with all other applicable flood hazard reduction provisions of this chapter.

(Ord. 1445, eff. August 14, 2014; as amended by Ord. 1500, eff. July 26, 2018)