Article V — 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 floodwaters around and away from proposed structures.

• C. Elevation and Floodproofing.

  1. Residential Construction. All new construction or substantial improvements of residential structures shall have the lowest floor, including basement:

     • a. In AE, AH, and A1-30 zones, elevated to or above the base flood elevation.

     • b. 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.

     • c. In an A zone, without BFEs specified on the FIRM (unnumbered A zone), elevated to or above the base flood elevation; as determined under Section 15.04.140(C).

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.

2. Nonresidential Construction. All new construction or substantial improvements of nonresidential structures shall either be elevated to conform with subsection (C)(1) of this section or:

   • a. Be floodproofed, together with attendant utility and sanitary facilities, 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 civil engineer or architect that the standards of subsections (C)(2)(a) and (b) of this section are satisfied. Such certification shall be provided to the floodplain administrator.

3. Flood Openings. All new construction and substantial improvements of structures 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 the following minimum criteria:

   • a. For nonengineered openings:

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

     • ii. The bottom of all openings shall be no higher than one foot above grade;

     • iii. 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

     • iv. Buildings with more than one enclosed area must have openings on exterior walls for each area to allow floodwater to directly enter; or

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

4. Manufactured Homes. See Section 15.04.200.

• Garages and Low Cost Accessory Structures.

• a. Attached Garages.

  • i. 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 floodwaters. See subsection (C)(3) of this section. Areas of the garage below the BFE must be constructed with flood resistant materials. See subsection B of this section.

  • ii. 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.

• b.

• Detached Garages and Accessory Structures.

• i. Accessory structures used solely for parking (two-car detached garages or smaller) or limited storage (small, low cost sheds), as defined in Article II of this chapter, 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:

  • (A) Use of the accessory structure must be limited to parking or limited storage;

  • (B) The portions of the accessory structure located below the BFE must be built using flood resistant materials;

  • (C) The accessory structure must be adequately anchored to prevent flotation, collapse and lateral movement;

  • (D) Any mechanical and utility equipment in the accessory structure must be elevated or floodproofed to or above the BFE;

  • (E) The accessory structure must comply with floodplain encroachment provisions in Section 15.04.220; and

  • (F) The accessory structure must be designed to allow for the automatic entry of floodwaters in accordance with subsection (C)(3) of this section.

• ii. Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in this section.

(Formerly 15.04.160; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

• 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.

• (Formerly 15.04.170; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

• A. All new subdivision proposals and other proposed development, including proposals for manufactured home parks and subdivisions, greater than fifty lots or five acres, whichever is the lesser, shall:

  1. Identify the special flood hazard areas (SFHA) and base flood elevations (BFE).

  2. Identify the elevations of lowest floors of 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:

  • a. Lowest floor elevation.

  • b. Pad elevation.

  • c. 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.

(Formerly 15.04.180; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

• A. All manufactured homes that are placed or substantially improved 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 upon which a manufactured home has incurred "substantial damage" as the result of a flood, shall:

  1. 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 or above the base flood elevation and be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

  2. Within Zones V1-30, V, and VE on the community's flood insurance rate map, meet the requirements of Section 15.04.230.

• 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, AE, V1-30, V, and VE 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 be elevated so that either the:

  1. Lowest floor of the manufactured home is at or 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 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.

(Formerly 15.04.190; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

• A. All recreational vehicles placed in Zones A1-30, AH, AE, V1-30 and VE will either:

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

  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 Section 15.04.150 and the elevation and anchoring requirements for manufactured homes in Section 15.04.200.

• B. Recreational 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 of this section and Section 15.04.230.

• (Formerly 15.04.200; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

Since floodways are an extremely hazardous area due to the velocity of floodwaters 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 foot at any point within the city of Cotati.

• B. Within an adopted regulatory floodway, the city of Cotati shall prohibit encroachments, including fill, new construction, substantial improvements, and other development, unless certification by a registered civil engineer is provided demonstrating that the proposed encroachment shall not result in any increase in flood levels during the occurrence of the base flood discharge.

• C. If subsections A and B of this section are satisfied, all new construction, substantial improvement, and other proposed new development shall comply with all other applicable flood hazard reduction provisions of this article.

• (Formerly 15.04.210; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

Within coastal high hazard areas, Zones V, V1-30, and VE, as established under Section 15.04.070, the following standards shall apply:

• A. All new residential and nonresidential construction, including substantial improvement/ damage, shall be elevated on adequately anchored pilings or columns and securely anchored to such pilings or columns so that the bottom of the lowest horizontal structural member of the lowest floor (excluding the pilings or columns) is elevated to or above the base flood level. The pile or column foundation and structure attached thereto is anchored to resist flotation, collapse, and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Water loading values used shall be those associated with the base flood. Wind loading values used shall be those required by applicable state or local building standards.

• B. All new construction and other development shall be located on the landward side of the reach of mean high tide.

• C. All new construction and substantial improvement shall have the space below the lowest floor free of obstructions or constructed with breakaway walls as defined in Article II of this chapter. Such enclosed space shall not be used for human habitation and will be usable solely for parking of vehicles, building access or storage.

• D. Fill shall not be used for structural support of buildings.

• E. Manmade alteration of sand dunes which would increase potential flood damage is prohibited.

• F. The floodplain administrator shall obtain and maintain the following records:

  1. Certification by a registered engineer or architect that a proposed structure complies with subsection A of this section; and

2. The elevation (in relation to mean sea level) of the bottom of the lowest horizontal structural member of the lowest floor (excluding pilings or columns) of all new and substantially improved structures, and whether such structures contain a basement.

(Formerly 15.04.220; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

Article VI Variance Procedure

The issuance of a variance is for floodplain management purposes only. Insurance premium rates are determined by statute according to actuarial risk and will not be modified by the granting of a variance.

The variance criteria set forth in this section of the ordinance are based on the general principle of zoning law that variances pertain to a piece of property and are not personal in nature. A variance may be granted for a parcel of property with physical characteristics so unusual that complying with the requirements of this chapter would create an exceptional hardship to the applicant or the surrounding property owners. The characteristics must be unique to the property and not be shared by adjacent parcels. The unique characteristic must pertain to the land itself, not to the structure, its inhabitants, or the property owners.

It is the duty of the city council to help protect its citizens from flooding. This need is so compelling and the implications of the cost of insuring a structure built below flood level are so serious that variances from the flood elevation or from other requirements in the flood ordinance are quite rare. The long-term goal of preventing and reducing flood loss and damage can only be met if variances are strictly limited. Therefore, the variance guidelines provided in this chapter are more detailed and contain multiple provisions that must be met before a variance can be properly granted. The criteria are designed to screen out those situations in which alternatives other than a variance are more appropriate.

(Formerly 15.04.250; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

• A. Generally, variances may be issued for new construction, substantial improvement, and other proposed new development to be erected on a lot of one-half acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level, providing that the procedures of Articles IV and V of this chapter have been fully considered. As the lot size increases beyond one-half acre, the technical justification required for issuing the variance increases.

• B. Variances may be issued for the repair or rehabilitation of "historic structures" (as defined in Article II of this chapter) upon a determination that the proposed repair or rehabilitation will not preclude the structure's continued designation as an historic structure and the variance is the minimum necessary to preserve the historic character and design of the structure.

• C. Variances shall not be issued within any mapped regulatory floodway if any increase in flood levels during the base flood discharge would result.

• D. Variances shall only be issued upon a determination that the variance is the "minimum necessary," considering the flood hazard, to afford relief. "Minimum necessary" means to afford relief with a minimum of deviation from the requirements of this chapter. For example, in the case of variances to an elevation requirement, this means the city council need not grant permission for the applicant to build at grade, or even to whatever elevation the applicant proposes, but only to that elevation which the city council believes will both provide relief and preserve the integrity of the local ordinance.

• E. Any applicant to whom a variance is granted shall be given written notice over the signature of a community official that:

  1. The issuance of a variance to construct a structure below the base flood level will result in increased premium rates for flood insurance up to amounts as high as twentyfive dollars for one hundred dollars of insurance coverage; and

  2. Such construction below the base flood level increases risks to life and property. It is recommended that a copy of the notice shall be recorded by the floodplain administrator in the office of the Sonoma County recorder and shall be recorded in a manner so that it appears in the chain of title of the affected parcel of land.

• F. The floodplain administrator will maintain a record of all variance actions, including justification for their issuance, and report such variances issued in its biennial report submitted to the Federal Emergency Management Agency.

• (Formerly 15.04.270; Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)

• A. In passing upon requests for variances, the city council shall consider all technical evaluations, all relevant factors, standards specified in other sections of this chapter, and the:

  1. Danger that materials may be swept onto other lands to the injury of others;

  2. Danger of life and property due to flooding or erosion damage;

  3. Susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the existing individual owner and future owners of the property;

  4. Importance of the services provided by the proposed facility to the community;

  5. Necessity to the facility of a waterfront location, where applicable;

  6. Availability of alternative locations for the proposed use which are not subject to flooding or erosion damage;

  7. Compatibility of the proposed use with existing and anticipated development;

  8. Relationship of the proposed use to the comprehensive plan and floodplain management program for that area;

  9. Safety of access to the property in time of flood for ordinary and emergency vehicles;

  10. Expected heights, velocity, duration, rate of rise, and sediment transport of the floodwaters expected at the site; and

  11. Costs of providing governmental services during and after flood conditions, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical, and water systems, and streets and bridges.

• B. Variances shall only be issued upon a:

  1. Showing of good and sufficient cause;

  2. Determination that failure to grant the variance would result in exceptional "hardship" to the applicant; and

  3. Determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, or extraordinary public expense, create a nuisance (see "Public safety and nuisance"), cause "fraud and victimization" of the public, or conflict with existing local laws or ordinances.

• C. Variances may be issued for new construction, substantial improvement, and other proposed new development necessary for the conduct of a functionally dependent use; provided, that the provisions of this section are satisfied and that the structure or other development is protected by methods that minimize flood damages during the base flood and does not result in additional threats to public safety and does not create a public nuisance.

• D. Upon consideration of the factors of Section 15.04.250(A) and the purposes of this chapter, the city council may attach such conditions to the granting of variances as it deems necessary to further the purposes of this chapter.

• (Ord. 667 § 2(part), 1997; Ord. 819 § 2(part), 2008)