Appendix G Flood-Resistant Construction

The purpose of this appendix is to promote the public health, safety and general welfare and to minimize public and private losses due to flood conditions in specific flood hazard areas through the establishment of comprehensive regulations for management of flood hazard areas designed to:

1. 1.

   Prevent unnecessary disruption of commerce, access and public service during times of flooding.

2. 2.

   Manage the alteration of natural flood plains, stream channels and shorelines.

3. 3.

   Manage filling, grading, dredging and other development that may increase flood damage or erosion potential.

4. 4.

   Prevent or regulate the construction of flood barriers that will divert floodwaters or that can increase flood hazards.

5. 5.

   Contribute to improved construction techniques in the flood plain.

The objectives of this appendix are to protect human life, minimize the expenditure of public money for flood control projects, minimize the need for rescue and relief efforts associated with flooding, minimize prolonged business interruption, minimize damage to public facilities and utilities, help maintain a stable tax base by providing for the sound use and development of flood-prone areas, contribute to improved construction techniques in the flood plain and ensure that potential owners and occupants are notified that property is within flood hazard areas.

The provisions of this appendix shall apply to all proposed development in a flood hazard area established in Section 1612 of this code, including certain building work exempt from permit under Section 105.2.

Any violation of a provision of this appendix, or failure to comply with a permit or variance issued pursuant to this appendix or any requirement of this appendix, shall be handled in accordance with Section 114.

The [INSERT JURISDICTION'S SELECTED POSITION TITLE] is designated as the floodplain administrator and is authorized and directed to enforce the provisions of this appendix. The floodplain administrator is authorized to delegate performance of certain duties to other employees of the jurisdiction. Such designation shall not alter any duties and powers of the building official.

The following words and terms shall, for the purposes of this appendix, have the meanings shown herein. Refer to Chapter 2 of this code for general definitions.

This appendix, in conjunction with this code, provides minimum requirements for development located in flood hazard areas, including:

1. 1.

   The subdivision of land.

2. 2.

   Site improvements and installation of utilities.

3. 3.

   Placement and replacement of manufactured homes.

4. 4.

   Placement of recreational vehicles.

5. 5.

   New construction and repair, reconstruction, rehabilitation or additions to new construction.

6. 6.

   Substantial improvement of existing buildings and structures, including restoration after damage.

7. 7.

   Installation of tanks.

8. 8.

   Temporary structures.

9. 9.

   Temporary or permanent storage, utility and miscellaneous Group U buildings and structures.

10. 10.

    Certain building work exempt from permit under Section 105.2 and other buildings and development activities.

Flood hazard areas are established in Section 1612.3 of this code, adopted by the applicable governing authority on [INSERT DATE].

All applications for permits shall comply with the following:

1. 1.

   The floodplain administrator shall review all permit applications to determine whether proposed development is located in flood hazard areas established in Section G103.2.

2. 2.

   Where a proposed development site is in a flood hazard area, all development to which this appendix is applicable as specified in Section G103.1 shall be designed and constructed with methods, practices and materials that minimize flood damage and that are in accordance with this code and ASCE 24.

It shall be the responsibility of the floodplain administrator to ensure that approval of a proposed development shall not be given until proof that necessary permits have been granted by federal or state agencies having jurisdiction over such development.

If design flood elevations are not specified, the floodplain administrator is authorized to require the applicant to meet one of the following:

1. 1.

   Obtain, review and reasonably utilize data available from a federal, state or other source.

2. 2.

   Determine the design flood elevation in accordance with accepted hydrologic and hydraulic engineering techniques. Such analyses shall be performed and sealed by a registered design professional. Studies, analyses and computations shall be submitted in sufficient detail to allow review and approval by the floodplain administrator. The accuracy of data submitted for such determination shall be the responsibility of the applicant.

In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the floodplain administrator shall not permit any new construction, substantial improvement or other development, including fill, unless the applicant submits an engineering analysis prepared by a registered design professional, demonstrating that the cumulative effect of the proposed development, when combined with all other existing and anticipated flood hazard area encroachment, will not increase the design flood elevation more than 1 foot (305 mm) at any point within the community.

Prior to issuing a permit for any floodway encroachment, including fill, new construction, substantial improvements and other development or land-disturbing activity, the floodplain administrator shall require submission of a certification, prepared by a registered design professional, along with supporting technical data, demonstrating that such development will not cause any increase of the base flood level.

Prior to issuing a permit for any alteration or relocation of any watercourse, the floodplain administrator shall require the applicant to provide notification of the proposal to the appropriate authorities of all adjacent government jurisdictions, as well as appropriate state agencies. A copy of the notification shall be maintained in the permit records and submitted to FEMA.

Prior to issuing a permit for any alteration of sand dunes and mangrove stands in coastal high-hazard areas and coastal A zones, the floodplain administrator shall require submission of an engineering analysis, prepared by a registered design professional, demonstrating that the proposed alteration will not increase the potential for flood damage.

The floodplain administrator shall maintain a permanent record of all permits issued in flood hazard areas, including supporting certifications and documentation required by this appendix and copies of inspection reports, design certifications and documentation of elevations required in Section 1612 of this code and Section R306 of the International Residential Code.

Development for which a permit under this appendix is required shall be subject to inspection. The floodplain administrator or the floodplain administrator’s designee shall make, or cause to be made, inspections of all development in flood hazard areas authorized by issuance of a permit under this appendix.

The floodplain administrator and the applicant shall not use changed flood hazard area boundaries or base flood elevations for proposed buildings or developments unless the floodplain administrator or applicant has applied for a conditional Flood Insurance Rate Map (FIRM) revision and has received the approval of the Federal Emergency Management Agency (FEMA).

Any person, owner or owner’s authorized agent who intends to conduct any development in a flood hazard area shall first make application to the floodplain administrator and shall obtain the required permit.

The applicant shall file an application in writing on a form furnished by the floodplain administrator. Such application shall:

1. 1.

   Identify and describe the development to be covered by the permit.

2. 2.

   Describe the land on which the proposed development is to be conducted by legal description, street address or similar description that will readily identify and definitely locate the site.

3. 3.

   Include a site plan showing the delineation of flood hazard areas, floodway boundaries, flood zones, design flood elevations, ground elevations, proposed fill and excavation and drainage patterns and facilities.

4. 4.

   Include in subdivision proposals and other proposed developments with more than 50 lots or larger than 5 acres (20 234 m²), base flood elevation data in accordance with Section 1612.3.1 if such data are not identified for the flood hazard areas established in Section G103.2.

5. 5.

   Indicate the use and occupancy for which the proposed development is intended.

6. 6.

   Be accompanied by construction documents, grading and filling plans and other information deemed appropriate by the floodplain administrator.

7. 7.

   State the valuation of the proposed work.

8. 8.

   Be signed by the applicant or the applicant’s authorized agent.

The issuance of a permit under this appendix shall not be construed to be a permit for, or approval of, any violation of this appendix or any other ordinance of the jurisdiction. The issuance of a permit based on submitted documents and information shall not prevent the floodplain administrator from requiring the correction of errors. The floodplain administrator is authorized to prevent occupancy or use of a structure or site that is in violation of this appendix or other ordinances of this jurisdiction.

A permit shall become invalid if the proposed development is not commenced within 180 days after its issuance, or if the work authorized is suspended or abandoned for a period of 180 days after the work commences. Extensions shall be requested in writing and justifiable cause demonstrated. The floodplain administrator is authorized to grant, in writing, one or more extensions of time, for periods not more than 180 days each.

The floodplain administrator is authorized to suspend or revoke a permit issued under this appendix wherever the permit is issued in error or on the basis of incorrect, inaccurate or incomplete information, or in violation of any ordinance or code of this jurisdiction.

The board of appeals established pursuant to Section 113, or other established or designed board, shall hear and decide requests for variances. The board shall base its determination on technical justifications, and has the right to attach such conditions to variances as it deems necessary to further the purposes and objectives of this appendix and Section 1612.

The floodplain administrator shall maintain a permanent record of all variance actions, including justification for their issuance.

A variance is authorized to be issued for the repair or rehabilitation of a historic structure 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.

A variance is authorized to be issued for the construction or substantial improvement of a functionally dependent facility provided that the criteria in Section 1612.1 are met and the variance is the minimum necessary to allow the construction or substantial improvement, and that all due consideration has been given to methods and materials that minimize flood damages during the design flood and do not create additional threats to public safety.

The board shall not issue a variance for any proposed development in a floodway if any increase in flood levels would result during the base flood discharge.

In reviewing applications for variances, the board shall consider all technical evaluations, all relevant factors, all other portions of this appendix and the following:

1. 1.

   The danger that materials and debris may be swept onto other lands resulting in further injury or damage.

2. 2.

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

3. 3.

   The susceptibility of the proposed development, including contents, to flood damage and the effect of such damage on current and future owners.

4. 4.

   The importance of the services provided by the proposed development to the community.

5. 5.

   The availability of alternate locations for the proposed development that are not subject to flooding or erosion.

6. 6.

   The compatibility of the proposed development with existing and anticipated development.

7. 7.

   The relationship of the proposed development to the comprehensive plan and flood plain management program for that area.

8. 8.

   The safety of access to the property in times of flood for ordinary and emergency vehicles.

9. 9.

   The expected heights, velocity, duration, rate of rise and debris and sediment transport of the floodwaters and the effects of wave action, if applicable, expected at the site.

10. 10.

    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 and water systems, streets and bridges.

Variances shall only be issued by the board where all of the following criteria are met:

1. 1.

   A technical showing of good and sufficient cause that the unique characteristics of the size, configuration or topography of the site renders the elevation standards inappropriate.

2. 2.

   A determination that failure to grant the variance would result in exceptional hardship by rendering the lot undevelopable.

3. 3.

   A determination that the granting of a variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, nor create nuisances, cause fraud on or victimization of the public or conflict with existing local laws or ordinances.

4. 4.

   A determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.

5. 5.

   Notification to the applicant in writing over the signature of the floodplain administrator that 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 $25 for $100 of insurance coverage, and that such construction below the base flood level increases risks to life and property.

Any subdivision proposal, including proposals for manufactured home parks and subdivisions, or other proposed new development in a flood hazard area shall be reviewed to verify all of the following:

1. 1.

   Such proposals are consistent with the need to minimize flood damage.

2. 2.

   Public utilities and facilities, such as sewer, gas, electric and water systems, are located and constructed to minimize or eliminate flood damage.

3. 3.

   Adequate drainage is provided to reduce exposure to flood hazards.

The following requirements shall apply in the case of any proposed subdivision, including proposals for manufactured home parks and subdivisions, any portion of which lies within a flood hazard area:

1. 1.

   The flood hazard area, including floodways, coastal high-hazard areas and coastal A zones, as appropriate, shall be delineated on tentative and final subdivision plats.

2. 2.

   Design flood elevations shall be shown on tentative and final subdivision plats.

3. 3.

   Residential building lots shall be provided with adequate buildable area outside the floodway.

4. 4.

   The design criteria for utilities and facilities set forth in this appendix and appropriate International Codes shall be met.

Development or land-disturbing activity shall not be authorized in the floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice, and prepared by a registered design professional, that the proposed encroachment will not result in any increase in the base flood level.

In coastal high-hazard areas and coastal A zones:

1. 1.

   New buildings and buildings that are substantially improved shall only be authorized landward of the reach of mean high tide.

2. 2.

   The use of fill for structural support of buildings is prohibited.

All new or replaced sanitary sewer facilities, private sewage treatment plants (including all pumping stations and collector systems) and on-site waste disposal systems shall be designed in accordance with Chapter 7, ASCE 24, to minimize or eliminate infiltration of floodwaters into the facilities and discharge from the facilities into floodwaters, or impairment of the facilities and systems.

All new or replacement water facilities shall be designed in accordance with the provisions of Chapter 7, ASCE 24, to minimize or eliminate infiltration of floodwaters into the systems.

Storm drainage shall be designed to convey the flow of surface waters to minimize or eliminate damage to persons or property.

Streets and sidewalks shall be designed to minimize potential for increasing or aggravating flood levels.

All new and replacement manufactured homes to be placed or substantially improved in a flood hazard area shall be elevated such that the top of the foundation for the manufactured home is at or above the design flood elevation.

All new and replacement manufactured homes, including substantial improvement of existing manufactured homes, shall be placed on a permanent, reinforced foundation that is designed in accordance with Section R306 of the International Residential Code.

All new and replacement manufactured homes to be placed or substantially improved in a flood hazard area shall be installed using methods and practices that minimize flood damage. Manufactured homes shall be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement. Methods of anchoring are authorized to include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.

Mechanical equipment and outside appliances shall be elevated to or above the design flood elevation.

Fully enclosed areas below elevated manufactured homes shall comply with the requirements of Section R306 of the International Residential Code.

The placement of recreational vehicles shall not be authorized in coastal high-hazard areas and in floodways.

Recreational vehicles in flood hazard areas shall be fully licensed and ready for highway use, or shall be placed on a site for less than 180 consecutive days.

Recreational vehicles that are not fully licensed and ready for highway use, or that are to be placed on a site for more than 180 consecutive days, shall meet the requirements of Section G109 for manufactured homes.

Underground and above-ground tanks shall be designed, constructed, installed and anchored in accordance with ASCE 24.

Garages and accessory structures shall be designed and constructed in accordance with ASCE 24, subject to the following limitations:

1. 1.

   In flood hazard areas other than coastal high-hazard areas and coastal A Zones, the floors of detached garages and detached accessory storage structures are permitted below the elevations specified in ASCE 24, provided that such structures are used solely for parking or storage, are one storyand not larger than 600 square feet (55.75 m²).

2. 2.

   In coastal high-hazard areas and coastal A Zones, the floors of detached garages and detached accessory storage structures are permitted below the elevations specified in ASCE 24, provided that such structures are used solely for parking or storage, are one storyand are not larger than 100 square feet (9.29 m²). Such structures shall not be required to have breakaway walls or flood openings.

Fences in floodways that have the potential to block the passage of floodwaters, such as stockade fences and wire mesh fences, shall meet the requirement of Section G104.5.

Oil derricks located in flood hazard areas shall be designed in conformance with the flood loads in Sections 1603.1.7 and 1612.

Retaining walls, sidewalks and driveways shall meet the requirements of Section 1804.5.

Swimming pools shall be designed and constructed in accordance with ASCE 24. Above-ground swimming pools, on-ground swimming pools and in-ground swimming pools that involve placement of fill in floodways shall also meet the requirements of Section G104.5.

Decks, porches and patios shall be designed and constructed in accordance with ASCE 24.

In coastal high-hazard areas and coastal A zones, nonstructural concrete slabs used as parking pads, enclosure floors, landings, decks, walkways, patios and similar nonstructural uses are permitted beneath or adjacent to buildings and structures provided that the concrete slabs shall be constructed in accordance with ASCE 24.

Roads and watercourse crossings that encroach into regulated floodways, including roads, bridges, culverts, low-water crossings and similar means for vehicles or pedestrians to travel from one side of a watercourse to the other, shall meet the requirement of Section G104.5.

Temporary structures shall be erected for a period of less than 180 days. Temporary structures shall be anchored to prevent flotation, collapse or lateral movement resulting from hydrostatic loads, including the effects of buoyancy, during conditions of the design flood. Fully enclosed temporary structures shall have flood openings that are in accordance with ASCE 24 to allow for the automatic entry and exit of floodwaters.

Temporary storage includes storage of goods and materials for a period of less than 180 days. Stored materials shall not include hazardous materials.

Temporary structures and temporary storage in floodways shall meet the requirements of G104.5.

Utility and miscellaneous Group U includes buildings that are accessory in character and miscellaneous structures not classified in any specific occupancy in this code, including, but not limited to, agricultural buildings, aircraft hangars (accessory to a one- or two-family residence), barns, carports, fences more than 6 feet (1829 mm) high, grain silos (accessory to a residential occupancy), greenhouses, livestock shelters, private garages, retaining walls, sheds, stables and towers.

Utility and miscellaneous Group U buildings and structures, including substantial improvement of such buildings and structures, shall be anchored to prevent flotation, collapse or lateral movement resulting from flood loads, including the effects of buoyancy, during conditions of the design flood.

Utility and miscellaneous Group U buildings and structures, including substantial improvement of such buildings and structures, shall be elevated such that the lowest floor, including basement, is elevated to or above the design flood elevation in accordance with Section 1612 of this code.

Fully enclosed areas below the design flood elevation shall be constructed in accordance with ASCE 24.

Flood-damage-resistant materials shall be used below the design flood elevation.

Mechanical, plumbing and electrical systems, including plumbing fixtures, shall be elevated to or above the design flood elevation.

See Table G115.1 for standards that are referenced in various sections of this appendix. Standards are listed by the standard identification with the effective date, standard title, and the section or sections of this appendix referenced in the standard.