Chapter 17.16
FLOOD HAZARD REDUCTION

Sections:

17.16.010    General standards.

17.16.020    Anchoring.

17.16.030    Construction materials and methods.

17.16.040    Utilities.

17.16.050    Subdivision proposals.

17.16.060    Review of building permits.

17.16.070    Specific standards.

17.16.080    Residential construction.

17.16.090    Nonresidential construction.

17.16.100    Manufactured homes.

17.16.110    Agricultural buildings.

17.16.115    Recreational vehicles.

17.16.120    Floodways.

17.16.130    Standards for shallow flooding areas (AO Zones).

17.16.140    Coastal high hazard areas.

17.16.010 General standards.

In all areas of special flood hazards the standards set forth in WCC 17.16.020 through 17.16.060 are required. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.020 Anchoring.

A. All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure.

B. All manufactured home must likewise be anchored to prevent flotation, collapse or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors (reference FEMA’s “Manufactured Home Installation in Flood Hazard Areas” guidebook for additional techniques). (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.030 Construction materials and methods.

A. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

B. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage. Electrical, heating, ventilation, plumbing and air-conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.040 Utilities.

A. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system.

B. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters.

C. On-site waste disposal systems shall be located to avoid impairment to them, or contamination from them, during flooding. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.050 Subdivision proposals.

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

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

C. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage.

D. Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed development which contain at least 50 lots or five acres (whichever is less). (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.060 Review of building permits.

Where elevation data is not available, either through the flood insurance study or from another authoritative source (WCC 17.12.030B), applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above grade in these zones may result in higher insurance rates. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.070 Specific standards.

In all areas of special flood hazards where base flood elevation data has been provided as set forth in WCC 17.04.050, Basis for establishing the areas of special flood hazards, or WCC 17.12.030B, Use of other base flood data, the provisions set forth in WCC 17.16.080 through 17.16.110 are required. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.080 Residential construction.

A. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to or above base flood elevation.

B. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:

1. 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 shall be provided;

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

3. Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of flood waters. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.090 Nonresidential construction.

New construction and substantial improvement of any commercial, accessory, agricultural, industrial or other nonresidential structure:

A. Shall either have the lowest floor, including basement, elevated to the level of the base flood elevation; or

B. Together with attendant utility and sanitary facilities, shall:

1. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water;

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

3. Be certified by a registered professional engineer or architect, that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be as set forth in WCC 17.12.030F and shall be provided by the applicant or required by the department of public works.

C. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in WCC 17.16.080B.

D. Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level (e.g., a building constructed to the base flood level will be rated as one foot below that level). (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.100 Manufactured homes.

All manufactured homes to be placed or substantially improved within Zones A1-30, AH, and AE shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is at or above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of Section 17.16.020B. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.110 Agricultural buildings.

Agricultural buildings shall comply with WCC 17.16.090. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.115 Recreational vehicles.

Recreational vehicles placed on sites within Zones A1-30, AH, AE and all V Zones on the community’s FIRM shall either:

A. Be on the site for fewer than 180 consecutive days; and

B. Be fully licensed and ready for highway use, on its wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and having no permanently attached additions; or

C. Meet the requirements of WCC 17.16.100 and anchoring requirements for manufactured homes. (Ord. 96-050 Exh A).

17.16.120 Floodways.

Located within areas of special flood hazard established in WCC 17.04.050 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

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

B. Construction or reconstruction of residential structures is prohibited within designated floodways, except for (i) repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and (ii) repairs, reconstruction or improvements to a structure, the cost of which does not exceed 50 percent of the market value of the structure either (a) before the repair, reconstruction, or improvement is started; or (b) if the structure has been damaged, and is being restored, before the damage occurred. Work done on structures to comply with existing health, sanitary, or other safety codes or to structures identified as historic places shall not be included in the 50 percent.

C. If WCC 17.16.120A is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this chapter. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.130 Standards for shallow flooding areas (AO Zones).

Shallow flooding areas appear on FIRMs as AO Zones with depth designations. The base flood depths in these zones range from one to three feet where a clearly defined channel does not exist, or where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is usually characterized as sheet flow. In these areas, the following provisions apply:

A. New construction and substantial improvements of residential structures within AO Zones shall have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, to or above the depth number specified on the FIRM (at least two feet if no depth number is specified).

B. New construction and substantial improvements of nonresidential structures within AO Zones shall either:

1. Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, to or above the depth number specified on the FIRM (at least two feet if no depth number is specified); or

2. Together with attendant utility and sanitary facilities, be completely floodproofed to or above that level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. If this method is used, compliance shall be certified by a registered professional engineer or architect as in WCC 17.16.090A.3.

C. Adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures shall be provided. (Ord. 96-050 Exh A; Ord. 87-25 (part)).

17.16.140 Coastal high hazard areas.

Located within areas of special flood hazard established in WCC 17.14.050 are coastal high hazard areas, designated as Zones V1-V30, VE and/or V. These areas have special flood hazards associated with high velocity waters from tidal surges and, therefore, in addition to meeting all provisions in this title, the following provisions shall also apply:

A. All new construction and substantial improvements in Zones V1-V30 and VE (V if base flood elevation data is available) shall be elevated on pilings and columns so that:

1. 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; and

2. 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. Wind and water loading values shall each have a one percent chance of being equalled or exceeded in any given year (100-year mean recurrence interval). A registered professional engineer or architect shall develop or review the structural design, specifications and plans for the construction and shall certify that the design and methods of construction to be used are in accordance with accepted standards of practice for meeting the provisions of 1 and 2 of this subsection.

B. Obtain the elevation (in relation to mean sea level) of the bottom of the lowest structural member of the lowest floor (excluding pilings and columns) of all new and substantially improved structures in Zones V1-30 and VE, and whether or not such structures contain a basement. The local administrator shall maintain a record of all such information.

C. All new construction shall be located landward of the reach of mean high tide.

D. Provide that all new construction and substantial improvements have the space below the lowest floor either free of obstruction or constructed with nonsupporting breakaway walls, open wood latticework, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. For the purpose of this section, a breakaway wall shall have a design safe loading resistance of not less than 10 and no more than 20 pounds per square foot. Use of breakaway walls which exceed a design safe loading resistance of 20 pounds per square foot (either by design or when so required by local or state codes) may be permitted only if a registered professional engineer or architect certifies that the designs proposed meet the following conditions:

1. Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and

2. The elevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and nonstructural). Maximum wind and water loading values to be used in this determination shall each have a one percent chance of being equalled or exceeded in any given year (100-year mean recurrence interval).

E. If breakaway walls are utilized, such enclosed space shall be usable solely for parking of vehicles, building access, or storage. Such space shall not be used for human habitation.

F. Prohibit the use of fill for structural support of buildings.

G. Prohibit manmade alteration of sand dunes which would increase potential flood damage. (Ord. 96-050 Exh A; Ord. 87-25 (part)).