Gwinnett County › Unified Development Ordinance

Title 3 — Development and Permitting, Chapter 700 — Floodplain Management

current as of 2025-10-28currency checked manuallyOfficialofficial source ↗5 sections · full chapter

§ 700-10

General Provisions

700-10.1 Findings.

A.The flood hazard areas of Gwinnett County are subject to periodic inundation which may result in loss of life and property, health and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood relief and protection, and impairment of the tax base, all of which adversely affect the public health, safety, and general welfare.

B.Flood hazard areas can serve important stormwater management, water quality, streambank protection, stream corridor protection, wetland preservation, and ecological purposes when permanently protected as undisturbed or minimally disturbed areas.

C.Effective floodplain management and flood hazard protection activities can:

1.Protect human life and health.

2.Minimize damage to private property.

3.Minimize damage to public facilities and infrastructure such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in floodplains.

4.Minimize expenditure of public money for costly flood control projects associated with flooding and generally undertaken at the expense of the general public.

D.Article IX, Section II of the Constitution of the State of Georgia and O.C.G.A. § 36-1-20(a), have delegated the responsibility to local governmental units to adopt regulations designed to promote the public health, safety, and general welfare of its citizenry. Therefore, Gwinnett County, Georgia, establishes this set of floodplain management and flood hazard reduction policies to regulate the use of flood hazard areas. It is determined that the regulation of flood hazard areas and the prevention of flood damage are in the public interest and will minimize threats to public health and safety, as well as to private and public property.

700-10.2 Requirements.

The requirements of Chapter 700 shall apply to all Areas of Special Flood Hazard within the jurisdiction of Gwinnett County.

700-10.3 Purpose.

It is the purpose of Chapter 700 to protect, maintain, and enhance the public health, safety, environment, and general welfare and to minimize public and private losses due to flood conditions in flood hazard areas, as well as to protect the beneficial uses of floodplain areas for water quality protection, streambank and stream corridor protection, wetlands preservation and ecological and environmental protection by provisions:

A.Restricting or prohibiting uses or activities which are dangerous to health, safety, and property due to flooding or erosion hazards, or which increase flood heights, velocities, or erosion.

B.Requiring that uses vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction or renovation.

C.Limiting the alteration of natural floodplains, stream channels, and natural protective barriers which are involved in the accommodation of flood waters.

D.Controlling filling, grading, dredging, and other development which may increase erosion or flood damage.

E.Preventing or regulating the construction of flood barriers which will unnaturally divert flood waters, or which may increase flood hazards to other lands.

F.Protecting stormwater management, water quality, streambank protection, stream corridor protection, wetland preservation and ecological functions of natural floodplain areas.

700-10.4 Flood Area Maps and Studies.

For the purposes of defining and determining "Area of Special Flood Hazard," "Areas of Future-conditions Flood Hazard," "Areas of Shallow Flooding," " Base Flood Elevations,"

"Floodplains," "Floodways," "Future-conditions Flood Elevations," "Future-conditions Floodplains," potential flood hazard or risk categories as shown on FIRM maps, and other terms used in Chapter 700, the following documents and sources may be used for such purposes and are adopted by reference thereto:

A.The Flood Insurance Study (FIS) dated September 29, 2006, or most current study, with accompanying maps and other supporting data and any revision thereto.

B.Other studies which may be relied upon for establishment of the base flood elevation (BFE) or delineation of the base or one percent (100-year) floodplain and flood-prone areas, including:

1.Any flood or flood related study conducted by the United States Army Corps of Engineers, the United States Geological Survey or any other local, State, or Federal Agency applicable to Gwinnett County.

2.Any base flood study conducted by a licensed professional engineer in the State of Georgia which has been prepared utilizing FEMA approved methodology and approved by the Department of Planning and Development.

C.Other studies which may be relied upon for establishment of the future conditions flood elevation or delineation of the future conditions floodplain and flood-prone areas, including:

1.Any flood or flood related study conducted by the United States Army Corps of Engineers, the United States Geological Survey or any other local, state, or federal agency applicable to Gwinnett County.

2.Any future-conditions flood study conducted by a licensed professional engineer in the State of Georgia which has been prepared utilizing FEMA approved methodology and approved by the Department of Planning and Development.

D.The repository for public inspection of the FIS, accompanying maps, and other supporting data is located at the following location:

Gwinnett County Department of Planning and Development 446 W Crogan Street, Suite 300 Lawrenceville, GA 30046

700-10.5 Interpretation.

A.In the interpretation and application of Chapter 700 all provisions shall be:

1.Considered as minimum requirements.

2.Liberally construed in favor of Gwinnett County.

3.Deemed neither to limit nor repeal any other powers granted under state statutes.

B.Where interpretation is needed as to the exact location of floodplain or floodway boundaries (for example, where there appears to be a conflict between a mapped boundary and actual field conditions) the Department shall make the necessary interpretation based on data submitted by the applicant. The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided in Chapter 700.

C.Where floodplain elevations have been defined, the floodplain shall be determined based on flood elevations rather than the area graphically delineated on the floodplain maps.

700-10.6 Drainage Easement Establishment.

On behalf of the public, a drainage easement is hereby established for the sole purpose of preserving and protecting the free flow of surface waters inside the future conditions flood contour elevations and along all watercourses. Where debris has accumulated in such a manner as would increase the need for flood protection, raise the flood level, or increase the risk of hazardous inundation of adjacent communities or jurisdictions, the County is hereby authorized to enter upon such watercourse and clear or remove such debris or obstructions as are hazardous to the public safety. The cost thereof shall be charged to the owner of the property where such debris and/or obstruction was generated. Where erosion has occurred in such a manner as would endanger a building or a structure, the County is hereby authorized to enter upon such watercourse and stabilize the channel for public safety. The cost thereof shall be charged to the owner of the property where the erosion has occurred and/or caused the erosion.

700-10.7 Establishment of Development Permit.

A development permit shall be required in conformance with the provisions of this UDO prior to the commencement of any clearing, grading, or development activities adjacent to, within, or affecting a future conditions floodplain.

700-10.8 Compliance.

No structure or use of land shall hereafter be located, extended, converted, or structurally altered without full compliance with the terms of Chapter 700 and other applicable regulations.

700-10.9 Compatibility with Other Regulations.

Chapter 700 is not intended to modify or repeal any other ordinance, rule, regulation, statute, easement, covenant, deed restriction, or other provision of law. The requirements of Chapter 700 are in addition to the requirements of any other ordinance, rule, regulation, or other provision of law, and where any provision of Chapter 700 imposes restrictions different from those imposed by any other ordinance, rule, regulation, or other provision of law, whichever provision is more restrictive or imposes higher protective standards for human health or the environment shall control.

700-10.10 Warning and Disclaimer of Liability.

The degree of flood protection required by Chapter 700 is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. Larger floods can and will occur on rare occasions. Flood heights may be increased by man-made or natural causes.

Chapter 700 does not imply that land outside the special flood hazard or flood-prone areas or uses permitted within such areas will be free from flooding or flood damages. Chapter 700 shall not create liability on the part of Gwinnett County or on the part of any officer or employee thereof for any flood damages that results from reliance on this Chapter, or any administrative decision lawfully made thereunder.

700-10.11 Duties and Responsibilities of Ordinance Administrator.

As the administrator of Chapter 700, the duties of the Director of the Department of Planning and Development or the Director's designee shall include, but shall not be limited to:

A.Review all development applications and permits to ensure that the requirements of Chapter 700 have been satisfied and to determine whether proposed building sites will be reasonably safe from flooding.

B.Require that copies of all necessary permits from governmental agencies from which approval is required by federal or state law, including but not limited to Section 404 of the Federal Water Pollution Control Act Amendments of 1972, 33 U.S.C. 1334, be provided and maintained on file.

C.When base flood elevation data or floodway data have not been provided, then the Director or Director's designee shall require the applicant to obtain, review and reasonably use any base flood elevation and floodway data available from a federal, state, or other sources in order to meet the requirements of Sections 700-20 and 700-30 and provisions of 700-40 herein.

D.Review and record the actual elevation in relation to mean sea level (or highest adjacent grade) of the lowest floor, including basement, of all new or substantially improved structures.

E.Review and record the actual elevation, in relation to mean sea level to which any substantially improved structures have been flood-proofed.

F.When flood-proofing is used for a non-residential structure, the director or director's designee shall review the design and operational maintenance plan and obtain certification of design criteria from a registered professional engineer or architect.

G.Notify affected adjacent communities and the Georgia Department of Natural Resources (GA DNR)

prior to any alteration or relocation of a watercourse and submit evidence of such notification to the Federal Emergency Management Agency (FEMA).

H.Where interpretation is needed as to the exact location of boundaries of the special flood hazard area (e.g., where there appears to be a conflict between a mapped boundary and actual field conditions) the director or director's designee shall make the necessary interpretation. Any person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation as provided in Chapter 120. Where floodplain elevations have been defined, the floodplain shall be determined based on flood elevations rather than the area graphically delineated on the floodplain maps.

I.All records pertaining to the provisions of Chapter 700 shall be maintained in the office of the Director or Director's designee and shall be open for public inspection.

J.Coordinate all FIRM revisions with the GA DNR and FEMA.

K.Review variance applications.

700-10.12 Severability.

If the provisions of any section, subsection, paragraph, subdivision, or clause of Chapter 700 shall be adjudged invalid by a court of competent jurisdiction, such judgment shall not affect or invalidate the remainder of any section, subsection, paragraph, subdivision, or clause of Chapter 700.

§ 700-20

Permit Procedures and Requirements

700-20.1 General Permit Procedures.

An application for a development permit on any property where a special flood hazard area is located or is proposed to be altered or disturbed in any way shall include, but not be limited to, the following in addition to the requirements of Section 330 of this UDO: plans drawn to scale of the property showing the floodplain, floodway and the nature, location, dimensions, and elevations of existing or proposed structures, fill, storage of materials, and drainage facilities.

700-20.2 Permit Application Requirements.

A.No owner or developer shall perform any development activity on a site where an Area of Special Flood Hazard or Area of Future-conditions Flood Hazard is located without first meeting the requirements of this ordinance prior to commencing the proposed activity.

B.Unless specifically excluded by this Chapter, any landowner or developer desiring a permit for development activity shall submit to Gwinnett County a permit application on a form provided for that purpose.

C.No permit will be approved for any development activities that do not meet the requirements, restrictions, and criteria of this Chapter.

700-20.3 Encroachments.

A.Application Procedure.

1.An application for a development permit which proposes any encroachment into, or alteration of a floodway shall, in addition to the requirements of Chapter 330 of this UDO, require submittal to the Department of complete plans and engineering calculations as required by Chapter 700 for "no-rise" certification.

2.The Department shall review and authorize such floodway encroachments prior to the issuance of a development permit and shall obtain from the applicant an engineering "no-rise"

certification signed by a professional engineer stating that the proposed development will not create any change to the pre-project base flood elevations, floodway elevations, or floodway widths.

3.If the applicant proposes to revise the floodway boundaries or base flood elevations, no permit authorizing an encroachment into or the alteration of the floodway shall be issued by the Department until an affirmative Conditional Letter of Map Revision (CLOMR) or Conditional Letter of Map Amendment (CLOMA), whichever is applicable, is issued and a " no-rise"

certification is approved by the Department.

4.An application for a map revision shall be submitted first to the Department. Record drawings and calculations shall be required to be provided to the Department by the applicant at the time of completion of the floodway encroachment.

5.Payment of any review fees associated with the review and approval of the encroachment shall be the responsibility of the applicant. Final plats or certificates of occupancy shall not be issued by the Department until an affirmative Letter of Map Revision (LOMR) or Letter of Map Amendment (LOMA), whichever is applicable, is issued.

B.Flood Levels Resulting from Floodway Encroachments. Located within Areas of Special Flood Hazard are areas designated as floodway. A floodway may be an extremely hazardous area due to the velocity of flood waters, debris, or erosion potential. In addition, floodways must remain free of encroachment in order to allow for the discharge of the base flood without increased flood heights.

Therefore, the following provisions shall apply:

1.Encroachments are prohibited, including but not limited to fill, new construction, substantial improvements, and other developments, within the regulatory floodway except for activities specifically allowed in Subsection 700-20.2.B.2 below.

2.Encroachments for bridges, culverts, roadways, and utilities within the regulatory floodway may be permitted provided it is demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the encroachment shall not result in any increase to the pre-project base flood elevations, floodway elevations, or floodway widths during the base flood discharge. A registered professional engineer must provide supporting technical data and certification thereof.

C.In areas where the floodplain has been established but the base flood elevation (BFE) and/or the floodway has not been established on FIS maps, no encroachments into areas of special flood hazard, including fill or structures, shall be authorized unless certification by a registered professional engineer is provided to the Department demonstrating that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the floodplain more than 0.01 foot at any point. The study shall be submitted as a revision/amendment to the FIS maps showing the BFE and the floodway. Approval of the revision/amendment must be received before the final plat can be approved or a certificate of occupancy can be issued.

D.In areas beyond the limits of study on the flood boundary and floodways maps or FIRM, which contains a watercourse, and have greater than 100 acres of surface drainage area above the property, no increase in flood elevations off-site shall be authorized.

700-20.4 Engineering Study Requirements.

An engineering study is required (as appropriate to the proposed development activities on the site) when a base flood or future conditions floodplain is located on the property proposed for development. This study shall be prepared by a currently registered professional engineer in Georgia and made a part of the application for a development permit. This information shall be submitted to and approved by the Department prior to the approval of any permit that would authorize the development. The engineering study shall contain, but not be limited to:

A.Description of the extent to which any watercourse or floodplain will be altered or relocated as a result of the proposed development.

B.Any report that must be submitted for review, in accordance with this Section, must use a step-backwater analysis approved by the Department. Cross-sections (which may be supplemented by the applicant) and flow information from the existing FIS will be obtained whenever available. Where applicable, computations will be shown duplicating FIS results and then computations will be rerun with the proposed modifications to determine the new base flood and future conditions flood profiles.

C.Floodplain storage calculations based on cross-sections (at least one every 100 feet) showing existing and proposed floodplain conditions must be provided to show that future conditions floodplain storage capacity will not be diminished by the development.

D.If changes to the base flood or future conditions flood elevation are proposed, profiles of the channel showing the existing and proposed base flood and future conditions flood elevations must be provided.

E.The study shall include a preliminary plat, grading plan, or site plan, as appropriate, which shall clearly define all future conditions of floodplain encroachments.

F.The floodway shall be determined when any encroachment in the floodplain is proposed, or a detailed study is performed to determine flood profiles.

G.Detailed flood studies in areas where the floodplain has been established but the Base Flood Elevation

(BFE)and/or the floodway has not been established and in areas beyond the limits of study on the FIRM, which may contain a watercourse, and have greater than 100 acres of surface drainage area above the property, shall be submitted showing the base flood elevations, future conditions flood elevations, and the floodway. Approval of the study must be received before the final plat of the affected lots can be approved or a Certificate of Occupancy can be issued.

700-20.5 Floodplain Management Plan and Plat Requirements.

An application for a development project with any Area of Special Flood Hazard or Area of Future-conditions Flood Hazard located on-site shall include a floodplain management/flood damage plan. This plan shall include the following items:

A.Site plan drawn to scale, which includes but is not limited to:

1.Existing and proposed elevations of the area in question and the nature, location, and dimension of existing and/or proposed structures, earthen fill placement, amount and location of excavation material, and storage of materials or equipment;

2.For all proposed structures, spot ground elevations at the building corners and 20-foot or smaller intervals along the foundation footprint, or one-foot contour elevations throughout the building site;

3.Proposed locations of water supply, sanitary sewer, and utilities;

4.Proposed locations of drainage and stormwater management facilities;

5.Proposed grading plan;

6.Base flood elevations and future-conditions flood elevations;

7.Boundaries of the base flood floodplain and future-conditions floodplain;

8.Location of the floodway, if applicable; and

9.Certification of the above by a licensed professional engineer or surveyor.

B.Building and foundation design detail, including but not limited to:

1.Elevation in relation to mean sea level (or highest adjacent grade) of the lowest floor, including the basement, of all proposed structures;

2.Design plans certified by a licensed professional engineer or architect for all proposed structure(s).

C.Hard copies and digital files of computer models, copy of work maps, comparison of pre- and post-development conditions base flood elevations, future-conditions flood elevations, flood protection elevations, Special Flood Hazard Areas and regulatory floodways, flood profiles and all other computations and other information similar to that presented in the FIS;

D.The approved floodplain management/flood damage prevention plan shall contain certification by the applicant that all development activities will be done according to the plan or previously approved revisions. All development permits and/or use and occupancy certificates or permits may be revoked at any time if the construction and development activities are not in accordance with approved plans.

E.All residential lots in a proposed subdivision shall have sufficient buildable area outside of the future conditions floodplain such that encroachments into the future-conditions floodplain for residential structures will not be required.

F.All preliminary plats and site development plans will provide the elevations of proposed structures in accordance with this Chapter.

G.All preliminary plats and site development plans shall be consistent with the need to minimize flood damage.

H.All construction plans for land development shall show public utilities and facilities such as water, sanitary sewer, gas, and electrical systems located and constructed to minimize or eliminate infiltration of flood waters, and discharges from the systems into flood waters.

I.All construction plans for land development include adequate drainage and stormwater management facilities per the requirements of Chapter 800 to reduce potential exposure to flood hazards.

700-20.6 Building Permit Requirements.

Prior to the issuance of a building permit for a site which contains or is adjacent to the floodplain, a drawing which shows the elevation of the proposed lowest floor of the building, including the basement, the limits of the floodplain, and the highest future conditions flood elevation and base flood elevation (100-year) adjacent to the building, must be submitted to the Department for approval. If the proposed development is located in multiple flood zones or multiple base flood elevations cross the proposed building site, the higher or more restrictive base flood elevation or future condition elevation and development standards shall take precedence at the building site. Proposed grading encroachments must be shown on this drawing. Elevations shall be referenced to an accurate topographical reference (e.g., a recorded final plat where the future conditions and the base floodplain is shown).

700-20.7 Other Permits or Approvals.

A.Copies of any additional federal or state permits or approvals as may be required by the Corps of Engineers, Georgia Department of Natural Resources, FEMA, or others shall be provided by the developer upon their approval and maintained on file in the Department of Planning and Development.

B.The Department shall notify adjacent communities and the Georgia Department of Natural Resources prior to any alteration or relocation of a watercourse and submit evidence of such notification to the Federal Emergency Management Agency (FEMA).

700-20.8 Construction Stage.

For all new construction and substantial improvements on sites with a floodplain management/ flood damage prevention plan which may be shown on a Residential Drainage Plan, the permit holder shall provide to Gwinnett County a certified as-built Elevation Certificate, or Floodproofing Certificate for non-residential construction, including the lowest floor elevation or floodproofing level immediately after the lowest floor or floodproofing is completed. A final Elevation Certificate shall be provided after completion of construction including final grading of the site. Any lowest floor certification made relative to mean sea level shall be prepared by or under the direct supervision of a licensed land surveyor or professional engineer and certified by the same. When floodproofing is utilized for non-residential structures, said certification shall be prepared by or under the direct supervision of a licensed professional engineer or architect and certified by same using the FEMA Floodproofing Certificate. This certification shall also include the design and operation/maintenance plan to ensure continued viability of the floodproofing measures.

Any work undertaken prior to submission and approval of the certification shall be at the permit holder's risk. No framing inspection shall be completed or approved by the Department until such required certification is received and verified by the Department. Deficiencies detected by such review shall be corrected by the permit holder immediately and prior to further progressive work being allowed to proceed. Failure to submit the survey or failure to make said corrections required thereby shall be cause to issue a stop work order for the project.

§ 700-30

Standards for Development

700-30.1 Definition of Floodplain Boundaries.

A.Studied "A" zones, identified in the Gwinnett County Flood Insurance Study identified in Section 700-10.4 shall be used to establish base flood elevations whenever available.

B.For all streams with a drainage area of 100 acres or greater, the base flood elevation and future conditions flood elevation shall be determined from the FIRM and FIS or provided by the Department.

If base flood elevation and future conditions flood elevation data is not available, then it shall be determined by a registered professional using FEMA approved methodology. The method of analysis shall be subject to the approval of the Department.

C.The boundaries or limits of the floodplain shall be within 0.5 feet vertical accuracy on the development plan containing existing topographic information.

700-30.2 Definition of Floodway Boundaries.

A.The width of a floodway shall be determined from the FIS or FEMA approved flood study. For all streams with a drainage area of 100 acres or greater, the regulatory floodway shall be provided by the Department. If floodway data is not available from the Department, then it shall be determined by a registered professional engineer using a method approved by FEMA and the Department.

B.Following a pre-design conference with the Department, the boundaries or limits of the floodway shall be shown on the development plan containing existing topographic information.

700-30.3 General Standards.

A.No development shall be allowed within any Area of Special Flood Hazard or Area of Future-conditions Flood Hazard that could result in any of the following:

1.Raise the base flood or future conditions flood elevation equal to or more than 0.01 foot.

2.Reduce the base flood or future conditions flood storage capacity.

3.Change the flow characteristics of the waters of the base flood or future conditions flood as they pass both the upstream and the downstream boundaries of the property. Verification shall be provided via a step-backwater analysis.

4.Create hazardous or erosion-producing velocities or result in excessive sedimentation.

B.Any development within any Area of Special Flood Hazard or Area of Future-conditions Flood Hazard allowed under 700-30.3 shall also meet the following conditions:

1.Compensation for storage capacity shall occur between the average ground water table elevation and the base flood elevation for the base flood, and between the average ground water table elevation and the future-condition flood elevation for the future-conditions flood. Compensation shall occur within the boundaries of ownership of the property being developed, or within a permanent, recorded flood control easement (which shall be a part of the Departmental record) and shall be within a reasonable proximity to the location of the encroachment. Acceptable means of providing required compensation include: lowering of natural ground elevations within the floodplain; or lowering of adjoining land areas to create additional floodplain; or raising of the future conditions flood elevation within the boundaries of ownership of the property being developed. All cut areas are to be graded to a slope of no less than two percent. In no case shall any required compensation be provided via bottom storage or by excavating below the elevation of the top of the natural (pre-development) stream channel unless such excavation results from widening or relocation of the stream channel.

2.Cut areas shall be stabilized to a slope of no less than 2.0 percent;

3.Verification of no-rise conditions, flood storage volumes, and flow characteristics shall be provided via a step-backwater analysis meeting the requirements of 700-20.4;

4.Effective transitions shall be provided such that flow velocities occurring on both upstream and downstream properties are not increased or decreased;

5.All proposed development shall have public utilities and facilities, such as sewer, gas, electrical and water systems, located and constructed to minimize or eliminate flood damage.

6.Any significant physical changes to the base flood floodplain shall be submitted as a Conditional Letter of Map Revision (CLOMR) or Conditional Letter of Map Amendment (CLOMA), whichever is applicable. The CLOMR submittal shall be subject to approval by the County using the FEMA Community Concurrence forms before forwarding the submittal package to FEMA for final approval. The responsibility for forwarding the CLOMR to FEMA and for obtaining the CLOMR approval shall be the responsibility of the applicant. Within six months of the completion of development, the applicant shall submit as-built surveys and plans for a final Letter of Map Revision (LOMR).

C.All subdivision proposals shall identify the Area of Special Flood Hazard and Areas of Future-conditions Flood Hazard therein and provide base flood elevation data and future-conditions flood elevation data.

1.All residential lots in a subdivision proposal shall have sufficient buildable area outside of the future-conditions floodplain such that encroachments into the future-conditions floodplain for residential structures will not be required; and

2.All subdivision plans will provide the elevations of proposed structures in accordance with Section 700-20.5.

700-30.4 Maintenance Requirements.

The property owner shall be responsible for continuing maintenance as may be needed within an altered or relocated portion of a floodplain on his property so that the flood-carrying or flood storage capacity is not diminished. Gwinnett County may direct the property owner (at no cost to the County) to restore the flood-carrying or flood storage capacity of the floodplain if the owner has not, in the opinion of the County pursuant to the approved plans and floodplain report on file with the Department, performed satisfactory maintenance.

§ 700-40

Provisions for Flood Damage Reduction

700-40.1 General Standards.

All new construction and substantial improvement of structures adjacent (residential or non-residential) to special flood hazard areas shall comply with the applicable requirements of the Gwinnett County Construction Code and the following:

A.Buildings/structures, including manufactured homes, shall not be allowed within the limits of the future-conditions floodplain;

B.Buildings/structures shall be constructed with materials and utility equipment resistant to flood damage;

C.Buildings/structures shall be constructed by methods and practices that minimize flood damage;

D.Electrical, heating, ventilation, plumbing, air conditioning equipment and other service facilities shall be constructed or located three (3) feet above the base flood elevation or one (1) foot above the future-conditions flood elevation, whichever is higher, so as to prevent water from entering or accumulating within the components during conditions of flooding;

E.New and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;

F.New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters;

G.New construction and substantial improvements of existing structures shall be anchored to prevent flotation, collapse, or lateral movement of the structure;

H.On-site waste disposal systems shall be located and constructed to avoid impairment to them or contamination from them during flooding;

I.Other public utilities such as gas and electric systems shall be located and constructed to avoid impairment to them, or public safety hazards from them, during flooding;

J.New development shall include adequate drainage and stormwater management facilities per requirement of Gwinnett County to reduce exposure to flood hazards;

K.Manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors.

This standard shall be in addition to and consistent with applicable state requirements for resisting wind forces;

L.When only a portion of a parcel is located within a flood zone or the future-conditions floodplain, all new and substantially improved structures on the parcel shall meet requirements of Chapter 700;

M.Any alteration, repair, reconstruction, or improvement to a structure which is not compliant with the provisions of Chapter 700, shall be undertaken only if the non-conformity is not furthered, extended, or replaced.

N.If the proposed development is located in multiple flood zones, or multiple base flood elevations cross the proposed site, the higher or restrictive base flood elevation or future condition elevation and development standards shall take precedence;

O.Subdivision proposals and other proposed new development, including manufactured home parks, shall be reasonably safe from flooding:

1.All such proposals shall be consistent with the need to minimize flood damage within the flood prone area;

2.All public utilities and facilities, such as sewer, gas, electrical, and water systems shall be located and constructed to minimize or eliminate flood damage; and

3.Adequate drainage shall be provided to reduce exposure to flood hazards.

700-40.2 Structures and Buildings Authorized in the Floodplain.

A.Residential Buildings.

1.New construction. New construction of principal residential structures shall not be allowed within the limits of the future-conditions floodplain.

2.Substantial improvements. For substantial improvements to all or part of an existing principal residential buildings, the requirements of Sections 700-20.1 through 700-20.3 and Sections 700-30.1 et seq., shall apply and the elevation of the lowest floor, including basement and access to the building, shall be elevated at least three feet above the level of the highest base flood elevation (100-year) adjacent to the building or at least 1 foot above the future conditions flood elevation whichever is highest. Openings sufficient to facilitate the unimpeded movements of flood waters shall be provided in accordance with Section 700-40.4 titled "Elevated buildings".

B.Non-Residential Buildings.

1.New construction. New construction of principal non-residential structures shall not be allowed within the limits of the future future-conditions floodplain.

2.Substantial improvements. Substantial improvements to all or part of an existing principal non-residential buildings may be authorized by the Department to be flood proofed in lieu of being elevated, in accordance with Section 700-40.4 titled "Elevated buildings", provided that all areas of the building less than 1 foot above the base flood elevation or below the future conditions flood elevation, whichever is highest, are watertight with walls substantially impermeable to the passage of water, and use structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. A registered professional engineer or architect shall certify to the Department that the standards of this subsection are satisfied and shall provide the Department a flood proofing certificate including flood proofing level immediately after flood proofing is completed. The certification shall be prepared by or under the direct supervision of a professional engineer or architect and certified by same. The requirements of Sections 700-20.1 through 700-20.3 and Sections 700-30.1, et seq., shall also apply.

C.Accessory and non-habitable buildings and structures. Accessory and non-habitable structures (i.e., barns, sheds, gazebos, and other similar structures) which are permitted to be located within the limits of the floodplain under the provisions of Title 2 of this UDO shall be designed and constructed of flood resistant materials to pass all floodwater and be anchored to prevent flotation, collapse, or lateral movement of the structure in a manner consistent with Chapter 700.

D.Drainage structures and impoundments. Drainage structures and impoundments may be authorized provided they are designed and constructed pursuant to the requirements of this UDO, are approved by the Department, and are consistent with the requirements of Chapter 700. Detention facilities may be located within the future conditions floodplain if the future conditions flood storage capacity is not reduced by the dam and water impounded behind the dam as required in Section 700-30.3.A.

E.Standards for Recreational Vehicles. All recreational vehicles placed on sites must either:

1.Be on the site for fewer than 180 consecutive days and be fully licensed and ready for highway use (a recreational vehicle is ready for highway use if it is licensed, on its wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached structures or additions).

2B. The recreational vehicle must meet all the requirements for residential buildings including the anchoring and elevation requirements.

F.Standards for Manufactured Homes.

1.New manufactured homes shall not be allowed to be placed within the limits of the future-conditions floodplain.

2.Manufactured homes placed and/or substantially improved in an existing manufactured home park or subdivision shall be elevated so that both:

i.The lowest floor of the manufactured home is elevated no lower than three (3) feet above the level of the base flood elevation, or one (1) foot above the future-conditions flood elevation, whichever is higher; and,

ii.The manufactured home chassis is elevated and supported by reinforced piers (or other foundation elements of at least an equivalent strength) of no less than 36 inches in height above grade.

3.All manufactured homes must be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement in accordance with standards of Section 700-40.1(K).

700-40.3 Structures and Buildings Authorized Adjacent to the Future Conditions Floodplain.

A.Residential buildings. For new construction or substantial improvement of any principal residential building or manufactured home, the elevation of the lowest floor, including the basement and access to the building, shall be at least three feet above the level of the highest base flood (100-year) elevation adjacent to the building or at least 1 foot above the future conditions flood elevation whichever is highest. Should solid foundation perimeter walls be used to elevate the structure, openings sufficient to automatically equalize the hydrostatic flood forces on exterior walls shall be provided in accordance with Section 700-40.4.

B.Non-residential buildings. For new construction or substantial improvement of any principal non-residential building, the elevation of the lowest floor, including the basement and access to the building, shall be at least 1 foot above the level of the highest base flood (100-year) elevation adjacent to the building or at least as high as the future conditions flood elevation whichever is highest. Should solid foundation perimeter walls be used to elevate the structure, openings sufficient to automatically equalize the hydrostatic flood forces on exterior walls shall be provided in accordance with Section 700-40.4.

700-40.4 Elevated Buildings.

All new construction or substantial improvements of existing structures that include any fully enclosed area located below the lowest floor formed by foundation and other exterior walls shall be designed to be an unfinished or flood resistant enclosure. The enclosure shall be designed to equalize hydrostatic flood forces on exterior walls by allowing for the automatic entry and exit of flood water.

A.Designs for complying with this requirement must either be certified by a professional engineer or architect or meet the following minimum criteria:

1.Provide a minimum of two openings having a total net area of not less than 1 square inch for every square foot of enclosed area subject to flooding.

2.The bottom of all openings shall be no higher than 1 foot above grade.

3.Openings may be equipped with screens, louvers, valves or other coverings or devices provided they permit the automatic flow of floodwater in both directions.

B.So as not to violate the "lowest floor" criteria of Section 700-40.1.A or Section 700-40.1.B, the unfinished or flood resistant enclosure shall only be used for parking of vehicles, limited storage of maintenance equipment used in connection with the premises, or entry to the elevated area.

C.The interior portion of such enclosed area shall not be partitioned or finished into separate rooms.

700-40.5 Building Standards for Residential Single-lot Developments on Streams without Established Base

Flood Elevations and/or Floodway (A-Zones). For a residential single-lot development not part of a subdivision that has areas of special flood hazard, where streams exist but no base flood data have been provided (A-zones), the Director shall review and reasonably use any available scientific or historic flood elevation data, base flood elevation and floodway data, or future conditions flood elevation data available from a federal, state, local or other source, in order to administer the provisions and standards of Chapter 700.

If data is not available from any of these sources, the following provisions shall apply:

A.No encroachments, including structures or fill material, shall be located within an area equal to twice the width of the stream or 50 feet from the top of the bank of the stream, whichever is greater.

B.In special flood hazard areas without base flood elevation or future conditions flood elevation data, new construction and substantial improvements of existing structures shall have the lowest floor of the lowest enclosed area (including basement) elevated no less than three feet above the highest adjacent grade at the building site. Openings sufficient to facilitate the unimpeded movements of floodwaters shall be provided in accordance with Section 700-40.6.

700-40.6 Building Standards for Areas of Shallow Flooding (AO-Zones).

Areas of Special Flood Hazard may include designated "AO" shallow flooding areas. These areas have base flood depths of one (1) to three (3) feet above ground, with no clearly defined channel. In these areas the following provisions apply:

A.All new construction and substantial improvements of residential and non-residential structures shall have the lowest floor, including the basement, elevated to no lower than one (1) foot above the flood depth number in feet specified on the Flood Insurance Rate Map (FIRM), above the highest adjacent grade. If no flood depth number is specified, the lowest floor, including basement, shall be elevated at least three (3) feet above the highest adjacent grade. Flood openings sufficient to facilitate automatic equalization of hydrostatic flood forces shall be provided in accordance with standards of Section 700-40.4;

B.New construction and substantial improvement of a non-residential structure may be floodproofed in lieu of elevation. The structure, together with attendant utility and sanitary facilities, must be designed to be watertight to the specified FIRM flood level plus one (1) foot above the highest adjacent grade, with walls substantially impermeable to the passage of water, and structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. A licensed professional engineer or architect shall certify that the design and methods of construction are in accordance with accepted standards of practice, and shall provide such certification to the (ordinance administrator) using the FEMA Floodproofing Certificate along with the design and operation/maintenance plan; and

C.Drainage paths shall be provided to guide floodwater around and away from any proposed structure.

§ 700-50

Variances

700-50.1 Variance Procedures.

A.Requests for variances from the requirements of Chapter 700 shall be submitted to the Department.

All such requests shall be heard and decided in accordance with the procedures outlined in the Gwinnett County Stormwater Management Manual and as set forth by the O.C.G.A. § 5-4-1 when certiorari shall lie. At a minimum, such procedures shall include notice to all affected parties and the opportunity to be heard.

B.Any person adversely affected by any decision of a request for variance shall have the right to appeal the decision to the Board of Construction Adjustments and Appeals in their normal course of business.

At a minimum, such procedures shall include notice to all affected parties and the opportunity to be heard.

700-50.2 Evaluation of Variance Requests.

A.In passing upon variance applications for relief from the provisions of Chapter 700, all technical evaluations, all relevant factors, all standards specified in other sections of this Chapter, and the items listed in the Gwinnett County Stormwater Management Manual shall be provided for review.

B.Upon consideration of the factors listed in the Gwinnett County Storm Sewer Pipe Standards and the stated purposes of Chapter 700, such conditions to the granting of a variance as the Board of Construction Adjustments and Appeals deems necessary or appropriate, consistent with the purposes of this Sections may be attached to the variance.

C.Variances shall not be approved within any designated floodway if any increase in flood levels outside the boundaries of ownership of the property being developed or drainage easement during the future conditions or the base flood discharge would result.

D.Variances may be issued for development necessary for the conduct of a functionally dependent use, provided the criteria of Chapter 700 are met, no reasonable alternative exists, and the development is protected by methods that minimize flood damage during the base flood and create no additional threats to public safety.

E.Any person requesting a variance shall, from the time of the request until the time the request is acted upon, submit such information and documentation as deemed necessary to the consideration of the request.

F.Variances shall not be issued "after the fact."

700-50.3 Historic Structures.

Variances from the requirements of Chapter 700 may be approved for the reconstruction, rehabilitation or restoration of structures listed on the National Register of Historic Places or the State Inventory of Historic Places, and provided the proposed reconstruction, rehabilitation, or restoration will not result in the structure losing its historical designation and provided further that the requirements of Section 700-50.4 herein are met.

700-50.4 Conditions for Variance Approval.

A.Variances shall only be approved upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief; and in the instance of a historical building, a determination that the variance is the minimum necessary so as not to destroy the historic character and design of the building.

B.Variances shall only be issued upon a finding of the following:

1.A showing of good and sufficient cause.

2.A determination that failure to grant the variance would result in exceptional hardship.

3.A determination that the granting of the variance will not result in increased flood heights, additional threats to public safety, extraordinary public expense, create nuisance, cause fraud on or victimization of the public, or conflict with existing local laws or ordinances.

C.No variance from the provisions of Chapter 700 may be approved which would allow a structure or use of land otherwise prohibited in the flood hazard area under the provisions of Title 2 of this UDO.

D.Any person to whom a variance is granted shall be given written notice specifying the difference between the base flood elevation and the elevation of the proposed lowest floor and stating that the cost of flood insurance will be commensurate with the increased risk to life and property resulting from the reduced lowest floor elevation.

700-50.5 Records and Reports.

The Department shall maintain the records of all appeal actions and report any variances to the Federal Emergency Management Agency upon request.