Chapter 14.12
FLOODPLAIN MANAGEMENT1

Sections:

14.12.010    Applicability.

14.12.015    Designation of the floodplain administrator.

14.12.020    Definitions.

14.12.030    Floodplain development permit.

14.12.040    Review of building permits.

14.12.050    Information to be obtained and maintained.

14.12.055    Elevation certificates.

14.12.060    Alteration of watercourses.

14.12.070    Performance standards – Flood hazard areas.

14.12.080    Construction materials and methods.

14.12.090    Utilities.

14.12.100    Subdivision and development proposals.

14.12.110    Residential construction.

14.12.120    Accessory structures.

14.12.130    Nonresidential construction.

14.12.140    Mobile and manufactured homes.

14.12.150    Recreational vehicles.

14.12.160    Shallow flooding areas.

14.12.170    Substantial improvement.

14.12.180    Repealed.

14.12.190    Critical facilities.

14.12.200    Floodways.

14.12.205    Hazardous materials.

14.12.210    Floodplain habitat assessment.

14.12.220    Critical area report.

14.12.230    Variances.

14.12.010 Applicability.

This chapter shall apply to all areas of special flood hazards (also referred to as “special flood hazard areas” or “SFHA”) within the city. Special flood hazard areas shall be as defined in NBMC 14.05.200(S)(4) as now in effect or as may be subsequently amended, which areas shall be determined by consideration of the following:

A. Basis for Establishing Areas of Special Flood Hazard. Special flood hazard areas identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study for King County, Washington, and Incorporated Areas” dated August 19, 2020, and any revisions thereto, with an accompanying flood insurance rate map (FIRM), and any revisions thereto, which are hereby adopted by reference as though fully set forth. The flood insurance study (FIS) and the FIRM are on file at North Bend City Hall at 920 Cedar Falls Way, North Bend, WA. The best available information for flood hazard area identification as outlined in subsection B of this section shall be the basis for regulation until a new FIRM is issued that incorporates data utilized under subsection B of this section; and

B. When base flood elevation data has not been provided (in A zone) in accordance with subsection A of this section, Basis for Establishing Areas of Special Flood Hazard, the floodplain administrator shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state, or other source, in order to administer the specific standards found in NBMC 14.12.100 through 14.12.140 and NBMC 14.12.200, Floodways.

C. In the event of a conflict, the more restrictive provision shall apply.

D. Compliance. All development within special flood hazard areas is subject to the terms of this chapter and other applicable regulations.

E. Penalties for Noncompliance. No structure shall hereafter be constructed, located, extended, converted, or altered, and no land shall be altered, without first complying with the terms of this chapter and other applicable regulations. Violations of the provisions of this chapter by failure to comply with any of its requirements, including violations of conditions attached to permits or other approvals, shall constitute a civil violation subject to the provisions of Chapters 1.20 and 8.08 NBMC and other applicable law. (Ord. 1726 § 12, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016: Ord. 1243 Exh. B (part), 2006).

14.12.015 Designation of the floodplain administrator.

The public works director is hereby appointed to administer, implement, and enforce this chapter by granting or denying development permits in accordance with its provisions. The floodplain administrator may delegate authority to implement these provisions. Duties of the floodplain administrator shall include, but not be limited to, reviewing all development permits to determine that:

A. The permit requirements of this chapter have been satisfied;

B. All other required state and federal permits have been obtained;

C. The site is reasonably safe from flooding;

D. The proposed development is not located in the floodway. If located in the floodway, assure the encroachment provisions of NBMC 14.12.200(B) are met; and

E. Notify FEMA when annexations occur in the special flood hazard area. (Ord. 1726 § 13, 2020).

14.12.020 Definitions.

To ensure consistency throughout all critical area regulations within the city, and except as otherwise set forth in this chapter, all definitions applicable to this chapter are set forth in NBMC 14.05.040. (Ord. 1726 § 14, 2020).

14.12.030 Floodplain development permit.

A. A floodplain development permit shall be obtained before new construction, substantial improvement, or development begins within any SFHA. The permit shall be for all structures, including mobile and manufactured homes or nonlicensed recreational vehicles on site for more than 180 days, as set forth in NBMC 14.12.140 and 14.12.150, and for all other development including fill and other activities as defined in NBMC 14.05.040.

B. Exemptions. The following uses and activities do not require a floodplain development permit, provided all applicable local, state, and federal requirements are met:

1. Maintenance of aboveground utilities and facilities, such as replacing power lines and utility poles;

2. Normal agricultural practices on existing agricultural areas involving plowing, storing of materials, etc., normal to operation of a farm (other than new structures);

3. Removal of noxious weeds, hazard trees, and replacement of non-native vegetation with native vegetation;

4. Routine maintenance of existing landscaping that does not involve clearing of native vegetation, grading, excavation, or filling;

5. Normal road maintenance, such as filling potholes, repaving, installing sign and traffic signals, but not including any expansion, increase of impervious surfaces, or distribution of native vegetation; and

6. Normal maintenance of a levee or other flood control facility as prescribed in the operations and maintenance plan for the facility. Normal maintenance does not include repair from flood damage, any expansion of the prism, face or toe expansion, or the addition of material for protection of armor.

C. The fee and/or review cost for a floodplain development permit shall be as set forth in the city’s taxes, rates and fees schedule, as now adopted or as may be amended from time to time.

D. The fee and/or review cost for a floodplain development permit shall be waived by the city when the permit is for a structure under 200 square feet in size.

E. The fee and/or review cost for a floodplain development permit shall be waived by the city when the permit is associated with a building permit for any of the following improvements:

1. Electrical repairs;

2. Furnace repairs or replacements;

3. Water heater or boiler repairs or replacements;

4. Air conditioner repairs or replacements;

5. Re-roofs;

6. Re-siding;

7. Insulation or simple weatherization or energy efficiency upgrades;

8. Roof-mounted or existing structure mounted solar collectors;

9. Window and door replacements; or

10. Renovation or remodel projects that cost less than $2,500;

provided, that waiver under subsections D and E of this section shall not apply if the project includes any other improvement not listed above, increases the structure’s floor area or footprint, causes a floodplain encroachment, or constitutes a substantial improvement under NBMC 14.12.170.

The cost of improvements that qualify for a waiver under subsections D and E of this section shall not be included in the cumulative calculation required by NBMC 14.12.170, unless the improvements are part of a substantial damage calculation or estimate.

F. Permit Application. Application for a floodplain development permit shall be made on forms furnished by the floodplain administrator. Required application materials as determined by the floodplain administrator may include:

1. Plans in duplicate drawn to scale showing the nature, location, dimensions, and elevations of the area in question, native vegetation, existing or proposed structures, fill, storage of materials, drainage facilities, and other information as identified on the application information sheet. These documents shall be maintained by the city for inspection of all records pertaining to the provisions of these critical areas regulations;

2. A critical areas report, if required, pursuant to Chapter 14.05 NBMC;

3. Habitat assessment, if required, pursuant to NBMC 14.12.210;

4. The base flood elevation in relation to the lowest floor (including basement) of all structures located in the AE zone or within the AO zone, shall be recorded on a current elevation certificate. Identify the highest adjacent natural grade next to the building prior to construction;

5. Proposed floodproofing elevation in relation to the base flood elevation or highest adjacent natural grade next to the building prior to construction;

6. Certification by a registered professional engineer or architect that the floodproofing methods for any nonresidential structure meet the floodproofing criteria in NBMC 14.12.130;

7. A description of the extent to which a watercourse will be altered or relocated as a result of a proposed development;

8. An elevation certificate for all new or substantially improved structures. When elevations are required, Section C of the elevation certificate must be completed and certified by a licensed professional land surveyor, as defined in RCW 18.43.020;

9. Where development is proposed in a floodway, an engineering analysis subject to the approval of the floodplain administrator indicating no rise of the base flood elevation; and

10. Any other information that may be reasonably required by the floodplain administrator in order to review the application.

G. All development permits for the site must be reviewed to ensure all necessary permits have been obtained from those federal, state, or local governmental agencies from which prior approval is required, prior to floodplain development permit issuance. (Ord. 1726 § 15, 2020; Ord. 1681 § 3, 2019: Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016: Ord. 1464 § 1 (Exh. A (part)), 2012; Ord. 1353 § 1 Exh. A (part), 2009; Ord. 1243 Exh. B (part), 2006. Formerly 14.12.050).

14.12.040 Review of building permits.

Where base flood elevation data is not available either through the Flood Insurance Study, FIRM, or from another authoritative source identified within NBMC 14.12.010(B), applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding; provided, that the elevation of the lowest floor (including basement) shall be at least two feet above the highest adjacent grade in those zones. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc., where available. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.050 Information to be obtained and maintained.

A. Where base flood elevation data is provided through the flood insurance study, FIRM, or other source in accordance with NBMC 14.12.010, the applicant shall obtain and record the actual (as-built) elevation (in relation to mean sea level) of the lowest floor (including basement) of all new or substantially improved structures, and whether or not the structure contains a basement.

B. For all new or substantially improved floodproofed nonresidential structures where base flood elevation data is provided through the FIS, FIRM, or other source in accordance with NBMC 14.12.010:

1. The applicant shall obtain and record the elevation (in relation to mean sea level) to which the structure was floodproofed; and

2. The city shall maintain the floodproofing certifications required in NBMC 14.12.130.

C. The city shall maintain:

1. Certification required by NBMC 14.12.200(B);

2. Records of all variance actions, including justification for their issuance;

3. Improvement and damage calculations; and

4. All records pertaining to the provisions of this chapter for public inspection. (Ord. 1726 § 16, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.055 Elevation certificates.

Three elevation certificates are required throughout the building process for all new structures and structures for which a substantial improvement as defined herein is proposed, unless the floodplain administrator determines an elevation certificate is not necessary for a specific structure:

A. For construction drawings, an elevation certificate is required with the building permit application;

B. An elevation certificate is required for a building under construction prior to scheduling of an underfloor inspection, or equivalent, but always before vertical construction; and

C. An elevation certificate is required for finished construction prior to issuance of a certificate of occupancy or final approval. Finished construction certificates will be reviewed for accuracy, and any required corrections must be made prior to acceptance of the certificate. (Ord. 1726 § 17, 2020).

14.12.060 Alteration of watercourses.

Adjacent communities and the Department of Ecology must be notified prior to any alteration or relocation of a watercourse, and evidence of such notification must be submitted to the Federal Insurance Administration. Assurance to the reasonable satisfaction of the floodplain administrator must be provided demonstrating that the flood carrying capacity of the altered or relocated portion of said watercourse is maintained. (Ord. 1726 § 18, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.070 Performance standards – Flood hazard areas.

The following standards apply to development proposals and alterations on sites within special flood hazard areas:

A. When fill is proposed to achieve elevated construction, a report by a registered professional engineer is required, demonstrating that the proposal will not increase the base flood elevation. If a development proposal will alter the base flood elevation or boundaries of the base flood elevation, then the project proponent shall provide the floodplain administrator with engineering documentation and analysis regarding the proposed change to demonstrate that no increased upstream or downstream flood hazard shall be created by the proposed development. If the change to the base flood elevation or boundaries of the SFHA would normally require a letter of map change, then the project proponent shall initiate, and receive approval of, a conditional letter of map revision (CLOMR) prior to approval of the development permit. The project shall be constructed in a manner consistent with the approved CLOMR.

If a CLOMR application is made, then the project proponent shall also supply the full CLOMR documentation package to the floodplain administrator to be attached to the floodplain development permit, including all required property owner notifications;

B. The following circumstances are presumed to produce no decrease in flood storage volume, and shall not require special studies to establish this fact:

1. Expansion of an existing structure that is no greater than 10 percent beyond its existing footprint, and that is outside of the floodway and outside of the AE zone where the floodway has not been mapped;

2. Development of new structures outside the FEMA floodway and outside of the AE zone where the floodway has not been mapped, where the area below the lowest floor allows for the automatic entry and exit of floodwaters;

3. Substantial improvements to existing residential structures in the floodplain but outside the FEMA floodway and outside of the AE zone where the floodway has not been mapped;

4. New development or substantial improvement in the area identified in the downtown commercial zoning district which is within the AO-1, AO-2, AO-3 or AE zone where the floodway has not been mapped and outside of the floodway; provided, that in the AE flood zone the difference between the highest adjacent grade of the site and the base flood elevation as measured on the flood insurance rate map is no greater than two feet; and/or

5. The improvement of all existing historic structures as defined by NBMC 14.05.040(H)(6);

C. The cumulative effect of any proposed development, where combined with all other existing and anticipated development on the site, shall not reduce the effective base flood storage volume of the floodplain. Except as exempted in subsection B of this section, grading or other activity that would reduce the effective base flood storage volume shall be mitigated by creating compensatory storage on site, or off site if legal arrangements can be made, to assure that the effective compensatory storage volume will be preserved over time in equivalent volume, at equivalent elevations to that being displaced. Compensatory storage areas must be hydraulically connected to the source of flooding, and no area below the waterline of a pond or other body of water can be credited as a compensating excavation; provided, however, that no increased upstream or downstream flood hazard shall be created by any fill authorized in the floodplain by this chapter or other applicable chapters;

D. If a lot has a buildable site or sites out of the special flood hazard area, all new structures shall be located there, when feasible. If a lot is fully in the floodplain, structures must be located to have the least impact on riparian habitat and listed species. All structures must be set back at least 15 feet from the protected area, as practicable. The city has prepared maps identifying the approximate boundaries of the protected area and the riparian habitat zone used to establish the protected area which are available on the city’s website. The protected area has been defined using the CMZs identified in the study titled “Channel Migration in the Three-Forks Area of the Snoqualmie River,” prepared by King County in January 1996. This study identified that little channel migration is expected to occur on the Middle Fork upstream from Tanner due to channel stability, nor on the South Fork upstream of the Burlington Northern Railroad (Snoqualmie Valley Trail) due to levee channelization. Therefore, channel migration was not used as a factor to determine the protected area within these reaches;

E. If the proposed project will create new impervious surfaces so that more than 10 percent of the portion of the lot in the regulatory floodplain is covered by impervious surface, the applicant shall demonstrate that there will be no net increase in the rate and volume of the stormwater surface runoff that leaves the site or that the adverse impact is mitigated per the approved habitat mitigation assessment;

F. Approved alterations shall not block side channel habitats; and

G. An analysis of bioengineering and/or vegetation enhancements will be required when existing levees or dikes are proposed to be repaired or renovated as specified in King County’s Guidelines for Bank Stabilization. (Ord. 1726 § 19, 2020; Ord. 1681 § 4, 2019: Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016: Ord. 1464 § 1 (Exh. A (part)), 2012; Ord. 1353 § 1 Exh. A (part), 2009; Ord. 1272 § 1, 2007; Ord. 1243 Exh. B (part), 2006. Formerly 14.12.020).

14.12.080 Construction materials and methods.

Construction materials and methods for residential and nonresidential structures shall meet the following criteria:

A. All construction elevated by pilings must be designed and certified by a professional structural engineer registered in the state of Washington and approved by the city building official;

B. All new construction or substantial improvements shall be constructed with materials and utility equipment resistant to flood damage, using methods and products that minimize flood damage;

C. Electrical, mechanical, plumbing, heating, ventilation and air conditioning and other service facilities shall be elevated or floodproofed to the flood protection elevation so as to prevent water from entering or accumulating within the components during conditions of flooding; and

D. All new construction and substantial improvements, including those related to manufactured homes, shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy. (Ord. 1726 § 20, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.090 Utilities.

Utilities and on-site sewage facilities shall meet the following criteria:

A. All new and replacement utilities including sewage treatment facilities shall be floodproofed to the flood protection elevation;

B. New on-site sewage disposal systems shall be located outside the limits of the floodway and may be installed in the floodplain if no feasible alternative site is available. On-site sewage disposal systems that are located within the flood hazard areas must be sited to avoid impairment of the system during flooding and to avoid contamination from the system during flooding;

C. Sewage and manure waste storage facilities, if allowed, shall be floodproofed to the flood protection elevation;

D. Buried utility transmission lines transporting hazardous substances (as defined by the Washington State Hazardous Waste Management Act in RCW 70.105.010) shall be buried a minimum of four feet beneath the maximum depth of scour of the base flood for the entire width of the floodway and shall achieve sufficient negative buoyancy so that any potential for flotation or upward migration is eliminated;

E. Aboveground utility transmission lines, not including electrical transmission lines, shall only be allowed in the floodway for the transportation of nonhazardous materials, as defined by the Washington State Department of Ecology, where a bridge or other structure is capable of transporting the line; and

F. Water wells shall be located on high ground that is not in the floodway. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.100 Subdivision and development proposals.

Applications for subdivisions, short subdivisions, master site plans, contract rezones, site plan/design review, planned residential developments, binding site plans, and other proposed development shall conform to the following requirements:

A. Be consistent with the need to minimize flood damage;

B. New buildable lots shall contain 5,000 square feet or more of buildable land outside the floodway;

C. Locate and construct all utilities and their facilities in a manner that minimizes flood damage;

D. Provide adequate drainage to reduce exposure to flood damage;

E. Base flood data and flood hazard notes shall be shown on the face of the recorded plat; this may include the floodwater depth, required flood elevations, and the boundary of the base flood and floodway as deemed appropriate by the city;

F. Where base flood elevation data has not been provided or is not available from another authorized source, it shall be generated for subdivision proposals and other proposed developments that contain at least 50 lots or five acres (whichever is less); and

G. The following note shall appear on the face of the recorded documents and shall be recorded on the title of records for all affected lots:

Note: Lots and structures located within special flood hazard areas may be inaccessible to emergency vehicles during flood events. Residents and property owners should take appropriate advance precautions to provide access.

(Ord. 1726 § 21, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.110 Residential construction.

New residential construction and substantial improvements within the SFHA shall meet the following criteria:

A. In AE and A1-30 zones or other A zoned areas where the base flood elevation has been determined or can be reasonably obtained, new construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated two feet or more above the base flood elevation. Mechanical equipment and utilities shall be waterproof or elevated at least two feet above the base flood elevation;

B. New construction and substantial improvement of any residential structure in an AO zone shall meet the requirements in NBMC 14.12.150;

C. New construction and substantial improvement of any residential structure in an unnumbered A zone for which a base flood elevation is not available and cannot be reasonably obtained shall be reasonably safe from flooding as determined by the floodplain administrator, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade;

D. 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 floodwaters. Designs must meet or exceed the following minimum criteria:

1. Have a minimum of two openings on two opposing walls with a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;

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

3. Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwater;

4. A garage attached to a residential structure, constructed with the garage floor slab below the base flood elevation, must be designed to allow for the automatic entry and exit of floodwaters;

5. Alternatively, a registered engineer or architect may design and certify engineered openings; and

6. If structures are constructed or substantially improved with fully enclosed areas below the lowest floor, the areas shall be used solely for parking of vehicles, building access, or storage;

E. Portions of the structure below the flood protection elevation must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawlspace used to elevate the building, but also any joists, insulation, or other materials that extend below the base flood elevation, in compliance with the most updated technical guidance published by FEMA; and

F. The elevation of the interior crawlspace grade must be at or above the lowest elevation of the exterior grade; provided, that below-grade crawlspace foundations may be allowed when all of the following conditions are met, in compliance with the most updated technical guidance published by FEMA:

1. The interior grade of the crawlspace below the base flood elevation is no more than two feet below the lowest adjacent exterior grade;

2. The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, does not exceed four feet at any point;

3. The crawlspace contains an adequate drainage system that removes floodwaters from the interior of the crawlspace, such as natural drainage through porous, well-drained soils, and/or constructed drainage systems such as perforated pipes, drainage tiles or gravel or crushed stone drainage by gravity or mechanical means;

4. Any building utility systems within the crawlspace are elevated to the flood protection elevation or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions. In particular, all ductwork is elevated above the design flood elevation or sealed from floodwaters;

5. The velocity of floodwaters at the site does not exceed five feet per second for any crawlspace; and

6. All other minimum criteria set forth in this section are satisfied. (Ord. 1726 § 22, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.120 Accessory structures.

This provision applies to accessory structures that are used for parking or limited storage only, such as garages or small storage sheds. Accessory structures that cannot meet the following standards shall be constructed following the requirements of NBMC 14.12.130. The following standards shall apply in the SFHA:

A. The accessory structure shall not have a floor area greater than 400 square feet;

B. Accessory structures shall be designed to have low flood damage potential and be considered a minimal investment;

C. Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters;

D. Accessory structures shall be firmly anchored to prevent flotation, collapse, and lateral movement;

E. Mechanical and utility equipment shall be floodproofed or elevated above the base flood elevation;

F. Floodway encroachment standards must be met;

G. The portions of accessory structures located below the base flood elevation must be constructed of flood-resistant materials; and

H. Accessory structures must be designed to allow for the automatic entry of floodwaters as described in NBMC 14.12.110(D), unless the floor is elevated above the base flood elevation. (Ord. 1726 § 23, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.130 Nonresidential construction.

A. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the requirements in this subsection A, or all of the requirements in subsection B of this section:

1. In AE and A1-30 zones or other A zoned areas where the base flood elevation has been determined or can be reasonably obtained:

New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated two feet or more above the base flood elevation, or elevated as required by ASCE 24, whichever is greater. Mechanical equipment and utilities shall be waterproofed or elevated least two feet above the base flood elevation, or as required by ASCE 24, whichever is greater.

2. If located in an AO zone, the structure shall meet the requirements in NBMC 14.12.150.

3. If located in an unnumbered A zone for which a base flood elevation is not available and cannot be reasonably obtained, the structure shall be reasonably safe from flooding as determined by the floodplain administrator, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade.

4. Portions of the structure below the flood protection elevation must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawlspace used to elevate the building, but also any joists, insulation, or other materials that extend below the base flood elevation, in compliance with the most updated technical guidance published by FEMA.

5. 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 floodwaters. 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, in compliance with the most updated technical guidance published by FEMA:

a. Have a minimum of two openings on opposing walls, with a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;

b. The bottom of all openings shall be no higher than one 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. If structures are constructed or substantially improved with fully enclosed areas below the lowest floor, the areas shall be used solely for parking of vehicles, building access, or storage.

B. If the requirements of subsection A of this section are not met, then new construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

1. Be dry floodproofed so that below two feet or more above the base flood level the structure is watertight with walls substantially impermeable to the passage of water or dry floodproofed to the elevation required by ASCE 24, whichever is greater;

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

3. Commercial, industrial, or other nonresidential structures that are elevated and not floodproofed must meet the same standards for space below the lowest floor as set forth in subsection (A)(4) of this section; and

4. Applicants who are 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 floodproofed to the base flood level will be rated as one foot below), and shall further be notified that floodproofing the building an additional foot will reduce insurance premiums. (Ord. 1726 § 24, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.140 Mobile and manufactured homes.

For all mobile and manufactured homes, all standards for flood hazard protection for residential construction shall apply. All new and substantially improved mobile and manufactured homes must be elevated on a permanent foundation to the flood protection elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement. (Ord. 1726 § 25, 2020; Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.150 Recreational vehicles.

Recreational vehicles placed on sites in the SFHA are required to either:

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

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

C. Meet the manufactured home elevation and anchoring requirements. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.160 Shallow flooding areas.

Shallow flooding zones appear on FIRMs as AO zones with depth designations. The base flood depths in these zones range from one to three feet above ground 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. Residential Structures. 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, two feet or more above the depth number specified on the FIRM (at least two feet if no depth number is specified);

B. Nonresidential Structures. New construction and substantial improvements of nonresidential structures that require a building permit within AO zones shall either:

1. Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one foot or more 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 defined under qualified professional. Where hazardous velocities were noted on the FIRM, consideration shall be given to mitigating the effects of these velocities through proper construction techniques and methods; or

C. Drainage for Residential and Nonresidential Structures. Adequate drainage paths around structures on slopes are required to guide floodwaters around and away from proposed structures. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016: Ord. 1243 Exh. B (part), 2006. Formerly 14.12.040).

14.12.170 Substantial improvement.

A project is considered a substantial improvement when the cost of any repairs, reconstruction, rehabilitation, addition, or improvement of a building or other structure equals or exceeds 50 percent of the market value of the structure (1) before the improvement or repair is started; or (2) if the structure has been damaged and is being restored, before the damage occurred. Substantial improvements are calculated on a cumulative basis, beginning with improvements commenced five years prior to the date of the current building permit application. When the total cost of all improvements within the five-year period equals or exceeds 50 percent of the market value of the structure, the project is considered a substantial improvement and the structure must be brought into compliance with this chapter. The cumulative calculation provision does not include tenant improvements of commercial structures, exclusions listed in NBMC 14.05.200(S)(12), or improvements that qualify for waiver under NBMC 14.12.030(E). (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.180 Additions.

Repealed by Ord. 1726. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.190 Critical facilities.

Critical facilities include, but are not limited to, schools, hospitals, police, fire and emergency response installations, nursing homes, wastewater treatment plants, potable water and sanitary sewer system components, and hazardous materials production. Construction of new critical facilities shall only be allowed within the floodplain when no reasonable alternative site is available. Critical facilities constructed within the floodplain shall have the lowest floor elevated to three or more feet above the level of the base flood elevation, except that factory assembled portable school classrooms shall have the lowest floor elevated to two feet or more above the base flood elevation. Floodproofing and sealing measures must be taken to ensure toxic or hazardous substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the 100-year frequency flood shall be provided to all critical facilities to the extent possible. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.200 Floodways.

Floodways are special flood hazard areas as determined in NBMC 14.12.010 due to the velocity of floodwaters that can actually carry debris and increase erosion potential. The following provisions apply in all designated floodways within the city:

A. Construction of new structures is prohibited within the floodway.

B. No-Rise Standard. Encroachments, including fill, new construction, substantial improvements or other developments, are prohibited unless certification by a registered professional engineer is provided demonstrating, through hydrologic and hydraulic analyses performed in accordance with standard engineering practice, that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge.

C. Construction or reconstruction of residential structures is prohibited within the floodway, except for projects that meet the following conditions:

1. Repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and

2. Repairs, reconstruction, or improvements to a structure, which are not considered a substantial improvement as defined in NBMC 14.20.190.

D. Any new construction and substantial improvement permitted under subsection B of this section shall comply with all other applicable flood hazard reduction standards of this chapter. (Ord. 1726 § 27, 2020; Ord. 1631 § 1, 2017: Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.205 Hazardous materials.

The storage or processing of chemicals, petroleum products or by-products, fertilizers, insecticides, pesticides, lime, cement, or other materials that, when inundated, will constitute a hazard to life, health and safety, or adversely affect the quality of surface waters is prohibited at or below three feet above the base flood elevation within the SFHA. (Ord. 1606 § 5 (part), 2016).

14.12.210 Floodplain habitat assessment.

A. Assessment Required. A floodplain habitat assessment is required unless the project is exempt under subsection B of this section. A habitat assessment determines if the project is likely to have no effect, not likely to adversely affect, or likely to adversely affect critical habitat or threatened and endangered species. If required, the habitat assessment shall be prepared at the applicant’s sole expense by a qualified consultant in accordance with the requirements of the Floodplain Habitat Assessment and Mitigation Regional Guidance 2013 prepared by FEMA Region X, or any successor guidance document approved by FEMA for habitat assessment and mitigation. The city’s actual costs of review of applicant’s habitat assessment and mitigation plan shall be paid by the applicant pursuant to the city’s adopted taxes, rates and fee schedule.

B. Exemptions. Any of the following activities do not require the preparation of a floodplain habitat assessment or consideration of associated mitigation measures, even if they may require a floodplain permit:

1. Nondevelopment activities pursuant to those set forth in NBMC 14.12.030(B);

2. Repairs or remodeling of an existing structure that qualifies for a fee exemption pursuant to NBMC 14.12.030(D), provided such work does not constitute a substantial improvement, a change in the structure’s footprint, or an increase in impervious surfaces;

3. Expansion of an existing structure that is no greater than 10 percent beyond its existing footprint; provided, that the repairs or remodeling are not a substantial improvement or repair of substantial damage;

4. Activities with the sole purpose of creating, restoring or enhancing natural functions associated with floodplains, streams, lakes, estuaries, marine areas, habitats, and riparian areas that meet federal and state standards, provided the activities do not include structures, grading, excavation, fill, or impervious surfaces;

5. Development of open space and recreational facilities, such as parks and trails, that do not include structures, grading, excavation, fill, impervious surfaces, or removal of more than five percent of the native vegetation on that portion of the property in the special flood hazard area;

6. Repair to on-site septic systems provided the ground disturbance is minimal and best management practices to prevent stormwater runoff and soil erosion are used;

7. Projects that have already received concurrence under another permit or other consultation with the U.S. Fish and Wildlife Service and/or the National Marine Fisheries Service, either through Section 7, Section 4d, or Section 10 of the Endangered Species Act, that address the entirety of the project in the floodplain (such as an Army Corps 404 permit or nonconversion forest practice activities including any interrelated and interdependent activities);

C. If the assessment conducted under subsection A of this section concludes the project is expected to have an adverse effect on Endangered Species Act (“ESA”) listed species and/or their critical habitat, the applicant shall provide a plan to mitigate those impacts, in accordance with the Floodplain Habitat Assessment and Mitigation Regional Guidance 2013 prepared by FEMA Region X.

1. If the USFWS or NMFS issues an incidental take permit under Section 10 of the ESA or a biological opinion under Section 7 of the ESA for the project in its entirety, then such may be considered to qualify as a plan to mitigate those impacts.

2. No compensatory mitigation is allowed within the protected area. Projects within the protected area must avoid short- and long-term direct and indirect effects including those of interrelated and interdependent activities.

3. If the project is located outside of the protected area, the mitigation plan shall include such avoidance, minimization, restoration, or compensation measures so that indirect adverse effects of development in the floodplain are mitigated such that equivalent or better habitat protection is provided.

4. The plan’s habitat mitigation activities shall be incorporated into the proposed project. The floodplain development permit shall be based on the redesign of the project and its mitigation components.

5. All work identified in the habitat assessment and mitigation plan shall be completed or assurances provided according to NBMC 14.05.090 (bonds or performance security) prior to issuance of the certificate of occupancy or final approval. (Ord. 1726 § 28, 2020; Ord. 1681 § 5, 2019: Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016).

14.12.220 Critical area report.

The director may waive a critical area report when existing mapping and flood insurance study is determined to be adequate. When a critical area report is required the following provisions shall apply:

A. A critical area report for flood hazard areas shall be prepared by an engineer or hydrogeologist, licensed in the state of Washington, with expertise analyzing geologic, hydrogeologic and surface and ground water flow systems, and who has experience preparing reports for the relevant type of hazard.

B. In addition to the requirements of Chapter 14.05 NBMC, critical area reports required for special flood hazard areas shall include the following information:

1. On the site map:

a. The dimensioned location of all proposed development in the floodplain;

b. Identification of all proposed structures and grading within the floodplain.

2. In the report:

a. Identify how the boundaries of the floodways and floodplain were determined; and

b. Establish the elevation of the lowest floor of all new or substantially improved structures proposed in the existing floodplain, utilizing the North American Vertical Datum of 1988. (Ord. 1606 § 5 (part), 2016: Ord. 1594 § 1 (part), 2016: Ord. 1464 § 1 (Exh. A (part)), 2012: Ord. 1243 Exh. B (part), 2006. Formerly 14.12.060).

14.12.230 Variances.

A. 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. The unique characteristic must pertain to the land itself, not to the structure, its inhabitants, or the property owners.

B. Variances to the requirements of this chapter shall only be issued:

1. Upon a determination by the floodplain administrator that the variance will not result in increased flood heights, additional unreasonable threats to public safety, extraordinary public expense, creation of public nuisances, or conflict with existing local laws or ordinances;

2. In the case of the repair, rehabilitation, or restoration of historic structures upon a determination that the proposed repair or rehabilitation will not preclude the structure’s continued designation as a historic structure and the variance is the minimum necessary to preserve the historic character and design of the structure;

3. Upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief;

4. Upon a determination that failure to grant the variance would result in unusual or exceptional hardship to the applicant;

5. Upon a showing that the use subject to the variance application cannot perform its intended purpose unless it is located or carried out in close proximity to water. This includes only facilities defined in Chapter 14.05 NBMC in the definition of “functionally dependent use”;

6. Variances may be issued for new construction and substantial improvements to be erected on a lot of one-half acre or less in size contiguous to and surrounded by one or more lots with existing structures constructed below the base flood elevation, provided the procedures set forth in this chapter have been fully considered. As the lot size increases beyond one-half acre, the technical justification required for issuing the variance increases;

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

C. In considering variance applications, the city of North Bend shall consider all technical evaluations, all relevant factors, all standards specified in other sections of this chapter, and:

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

2. The danger to life and property due to flooding or erosion damage;

3. The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner;

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

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

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

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

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

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

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

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

D. Any applicant to whom a variance is granted shall be given written notice over the signature of the floodplain administrator that:

1. The issuance of a variance to construct a structure below the BFE will result in increased premium rates for flood insurance up to amounts as high as $25.00 for $100.00 of insurance coverage; and

2. Such construction below the BFE increases risks to life and property.

E. The floodplain administrator may approve variances to the nonresidential elevation and dry floodproofing standards in NBMC 14.12.130 for accessory structures and agricultural structures as follows:

1. The structure shall not be used by the public, such as a place of employment or entertainment, or used as temporary or seasonal living quarters, or have one or more uses that do not meet the definition of an accessory structure or agricultural structure;

2. The building shall not be used in a manner that would create a threat to public safety, health and welfare, such as but not limited to confinement operations; structures with liquified natural gas terminals; and facilities producing and storing highly volatile, toxic or water-reactive materials;

3. The building shall have low damage potential given the characteristics of the building’s construction and the base flood;

4. The building shall be constructed and placed on the site so as to offer the minimum resistance to the flow of floodwaters;

5. The portions of the building below the flood protection elevation shall be constructed with flood-resistant materials;

6. Building utilities shall not be installed except electrical fixtures, which must be elevated or floodproofed to or above the flood protection elevation;

7. The building shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters, as described in NBMC 14.12.130(A)(5);

8. The building shall not have all sides of the building below grade;

9. The building shall comply with the standards in NBMC 14.12.200;

10. The applicant shall demonstrate that the strict enforcement of the standards of this section would result in exceptional hardship to the property owner.

F. The floodplain administrator shall maintain a record of all variance applications, including the basis for final decision on such applications.

G. The floodplain administrator may condition the variance as needed to ensure that the requirements and criteria of this chapter are met. (Ord. 1726 § 29, 2020).


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Prior legislation: Ords. 951 and 1088.