§ 25-12-54 - FLOOD-RESISTANT CONSTRUCTION.
(A) Statutory Authorization. As a home-rule city, the City of Austin has the responsibility and power to adopt regulations designed to minimize flood losses. The Legislature of the State of Texas has in Sections 16.3145 and 16.315 of the Texas Water Code authorized local government units to adopt regulations designed to minimize flood losses.
(B) Administration.
(1) Purpose. The purpose of this section 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:
(a) prevent unnecessary disruption of commerce, access and public service during times of flooding;
(b) manage the alteration of natural flood plains, stream channels and shorelines;
(c) manage filling, grading, dredging and other development which may increase flood damage or erosion potential;
(d) prevent or regulate the construction of flood barriers which will divert floodwaters or which can increase flood hazards;
(e) contribute to improved construction techniques in the flood plain;
(f) restrict or prohibit uses that are dangerous to health, safety or property in times of flood, or cause excessive increases in flood heights or velocities; and
(g) require that uses vulnerable to floods, including facilities which serve such uses, be protected against flood damage at the time of initial construction.
(2) Objectives. The objectives of this section 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.
(3) Scope. The provisions of this section shall apply to all proposed development in a flood hazard area established in Section 25-12-53 (Flood Loads) of this code.
(4) Alternative provisions. As an alternative to the requirements applicable to building and structures subject to Article 11 (Residential Code), ASCE 24 is permitted subject to the limitations of this code and the limitations therein.
(5) Structural systems. Structural systems of buildings and structures shall be designed, connected and anchored to resist flotation, collapse or permanent lateral movement due to structural loads and stresses from flooding equal to the design flood elevation.
(6) Flood-resistant construction. Buildings and structures erected in areas prone to flooding shall be constructed by methods and practices that minimize flood damage.
(C) Applicability.
(1) General. This section, in conjunction with other applicable provisions in this chapter, provides minimum requirements for development located in flood hazard areas, including:
(a) the subdivision of land;
(b) site improvements and installation of utilities;
(c) placement and replacement of manufactured homes;
(d) placement of recreational vehicles;
(e) new construction and repair, reconstruction, rehabilitation, or additions to new construction;
(f) substantial improvement of existing buildings and structures, including restoration after damage; and
(g) the installation of tanks.
(2) Abrogation and greater restrictions. This section is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this section and another city code provision, easement, covenant, or deed restriction conflict or overlap, whichever imposes the more stringent restrictions shall prevail.
(3) Establishment of flood hazard areas. Flood hazard areas are established in Section 25-12-53(B) (Establishment of flood hazard areas).
(4) Nonconforming Uses. A structure, or the use of a structure or premises, which was lawful before the adoption of the Building Code, but which does not conform with the requirements of these regulations, may be continued subject to the following conditions:
(a) No such use shall be expanded, changed, enlarged, or altered in a way which increases its nonconformity.
(b) No substantial improvement of the structure shall be made unless the structure is changed to conform to these regulations.
(c) If a nonconforming use is discontinued for a period of 90 days, any future use of the building or premises shall conform to these regulations.
(d) Any nonconforming use or structure which is destroyed by any means, including floods, to an extent of 50 percent or more of its market value, shall not be reconstructed except in conformance with the provisions of these regulations.
(D) Powers and Duties.
(1) Permit applications. All applications for permits shall comply with the following:
(a) The building official shall review all permit applications to determine whether proposed development is located in flood hazard areas established in Section 25-12-53(B) (Establishment of flood hazard areas).
(b) Where a proposed development site is in a flood hazard area, all development to which this section is applicable as specified in Subsection (C)(1) (General) shall be designed and constructed with methods, practices and materials that minimize flood damage and that are in accordance with the applicable provisions in Chapter 25-12 (Technical Code) and ASCE 24.
(2) Other Permits. It shall be the responsibility of the building official to ensure that approval of a proposed development shall not be given until proof that necessary approvals and/or permits have been granted by federal, state, or local agencies having jurisdiction over such development.
(3) Establishing the design flood elevation. The design flood elevation defines areas prone to flooding and describes, at a minimum, the base flood elevation at the depth of peak elevation of flooding based upon:
(a) For areas amended to incorporate Atlas 14 data, the 100-year floodplain calculated under fully developed conditions in accordance with the City of Austin Drainage Criteria Manual as amended to incorporate Atlas 14 data;
(b) For areas not yet amended to incorporate Atlas 14 data, the 500-year floodplain either as depicted on the FEMA Flood Insurance Rate Map as of January 6, 2016, as subsequently revised, or as calculated under existing conditions as prescribed by the Drainage Criteria Manual using data predating Atlas 14; or
(c) For the Colorado River, the 100-year floodplain as depicted on the FEMA Flood Insurance Rate Map dated January 6, 2016, or as subsequently revised.
(4) Determination of design flood elevations. If design flood elevations are not specified, the building official is authorized to require the applicant to:
(a) Obtain, review and reasonably utilize data available from a federal, state or other source; or
(b) Determine the design flood elevation in accordance with the 100-year floodplain as defined in the Austin City Code. Such analyses shall be performed and sealed by a Professional Engineer licensed by the State of Texas. Studies, analyses and computations shall be submitted in sufficient detail to allow review and approval by the building official. The accuracy of data submitted for such determination shall be the responsibility of the applicant.
(5) Determination of impacts. In a riverine flood hazard area where design flood elevations are specified but floodways have not been designated, an applicant shall demonstrate that the effect of the proposed building or structure on design flood elevations, including fill, when combined with all other existing and anticipated flood hazard area encroachments, will not increase the design flood elevation at any point within the jurisdiction.
(6) Activities in riverine flood hazard areas. In riverine situations, the building official 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 development, will not increase the design flood elevation at any point that results in additional adverse flooding on other property.
(7) Lowest floor. The lowest floor shall be the floor of the lowest enclosed area, including basement. The lowest floor does not include any unfinished flood-resistant enclosure that is used only for vehicle parking, building access, or limited storage, unless the enclosure is built to cause the building or structure to violate this section.
Exception: An unfinished enclosure used for storage of property, materials, or equipment that constitute a safety hazard if contacted by flood waters is a lowest floor.
(8) Protection of mechanical, plumbing and electrical systems. Electrical systems, equipment and components; heating, ventilating, air-conditioning; plumbing appliances and plumbing fixtures; duct systems; and other service equipment shall be located at or above the elevation required in Section 25-12-53(C)(1) (Elevation Requirements). If replaced as part of a substantial improvement, electrical systems, equipment and components; heating, ventilating, air-conditioning and plumbing appliances and plumbing fixtures; duct systems; and other service equipment shall meet the requirements of this section. Systems, fixtures, and equipment and components shall not be mounted on or penetrate through walls intended to break away under flood loads.
Exception: Locating electrical systems, equipment and components; heating, ventilating, air-conditioning; plumbing appliances and plumbing fixtures; duct systems; and other service equipment is permitted below the elevation required in Section 25-12-53(C)(1) (Elevation Requirements) provided that they are designed and installed to prevent water from entering or accumulating within the components and to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to the required elevation in accordance with ASCE 24. Electrical wiring systems are permitted to be located below the required elevation provided that they conform to the provisions of the electrical part of this code for wet locations.
(9) Protection of water supply and sanitary sewage systems. New and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the systems in accordance with the plumbing provisions of this code. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into systems and discharges from systems into floodwaters in accordance with the plumbing provisions of this code and Chapter 3 of the International Private Sewage Disposal Code.
(10) Flood-resistant materials. Building materials and installation methods used for flooring and interior and exterior walls and wall coverings below the elevation required in Section 25-12-53(C)(1) (Elevation Requirements) shall be flood damage-resistant materials that conform to the provisions of FEMA TB-2.
(11) Floodway encroachment. Prior to issuing a permit for any floodway encroachment, including fill, new construction, substantial improvements and other development or land-disturbing activity, the building official shall require submission of a certification prepared by a Professional Engineer licensed by the State of Texas, along with supporting technical data in accordance with the City of Austin Drainage Criteria Manual, demonstrating that such development will not cause any increase of the level of the design flood.
(12) Floodway revisions. A floodway encroachment that increases the level of the design flood may be considered for a variance only if the applicant has applied for a conditional Flood Insurance Rate Map (FIRM) revision and has received the approval of the Federal Emergency Management Agency (FEMA) provided the conditional Flood Insurance Rate Map (FIRM) revision is required by the City of Austin Drainage Criteria Manual.
(13) Watercourse alteration. Prior to issuing a permit for any alteration or relocation of any watercourse, the building official shall require the applicant to provide notification of the proposal to the appropriate authorities of all affected 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.
(14) Engineering analysis. The building official shall require submission of an engineering analysis in accordance with the City of Austin Drainage Criteria Manual performed and sealed by a Professional Engineer licensed by the State of Texas demonstrating that the flood-carrying capacity of the altered or relocated portion of the watercourse will not be decreased. Such watercourses shall be maintained in a manner which preserves the channel's flood-carrying capacity.
(15) Records. The building official shall maintain a permanent record of all permits issued in flood hazard areas, including copies of inspection reports and certifications required in Section 25-12-53(D) (Flood hazard documentation).
(16) Inspections. Development for which a permit under this section is required shall be subject to inspection. The building official or the building official'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 section.
(E) Permits.
(1) Required. 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 building official and shall obtain the required permit.
(2) Application for permit. The applicant shall file an application in writing on a form furnished by the building official. Such application shall:
(a) Identify and describe the development to be covered by the permit.
(b) 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.
(c) Include a site plan showing the delineation of flood hazard areas, floodway boundaries, flood zones, design flood elevations, ground elevations, proposed lowest floor elevation, proposed fill and excavation and drainage patterns and facilities.
(d) Include in subdivision proposals and other proposed developments with more than 50 lots or larger than 5 acres (20,234 m 2 ), base flood elevation data in accordance with Section 25-12-53(B) (Establishment of flood hazard areas).
(e) Indicate the use and occupancy for which the proposed development is intended.
(f) Be accompanied by construction documents, grading and filling plans and other information deemed appropriate by the building official.
(g) State the valuation of the proposed work.
(h) Be signed by the applicant or the applicant's authorized agent.
(3) Validity of permit. The issuance of a permit under this section shall not be construed to be a permit for, or approval of, any violation of this section or any other ordinance of the jurisdiction. The issuance of a permit based on submitted documents and information shall not prevent the building official from requiring the correction of errors. The building official is authorized to prevent occupancy or use of a structure or site which is in violation of this section or other ordinances of the City of Austin.
(4) Time Limitation on Application; Permit Expiration and Reactivation. Article 13 (Administration of Technical Codes) of this chapter establishes permit application time limits and requirements applicable to permit expiration and reactivation, including a review fee for expired permits.
Exception: Permits issued under Section 105.1.1 (Annual permit) are only valid for a period of 360 days from the date of issuance and cannot be extended.
(5) Suspension or revocation. The building official is authorized to suspend or revoke a permit issued under this section 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 the City of Austin.
(F) Variances.
(1) General. The City Council shall decide requests for variances from the floodplain regulations in this code and Chapter 25-7 (Drainage) after conducting a public hearing. The City Council 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 article.
(2) Records. The building official shall maintain a permanent record of all variance actions, including justification for their issuance.
(3) Historic structures. A variance may 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.
Exceptions: Within flood hazard areas, historic structures that are not:
(a) listed or preliminarily determined to be eligible for listing in the National Register of Historic Places; or
(b) determined by the Secretary of the U.S. Department of Interior as contributing to the historical significance of a registered historic district or a district preliminarily determined to qualify as a historic district; or
(c) designated as historic under a state or local historic preservation program that is approved by the Department of Interior.
(4) Functionally dependent facilities. A variance may be issued for the construction or substantial improvement of a functionally dependent facility provided the criteria in Section 25-12-53(A) (General) 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 create no additional threats to public safety.
(5) Restrictions. The City Council shall not issue a variance for any proposed development in a floodway if any increase in flood levels would result during the design flood discharge.
(6) Considerations. In reviewing applications for variances, the City Council shall consider all technical evaluations, all relevant factors, all other portions of this section, and each of the following:
(a) The danger that materials and debris may be swept onto other lands resulting in further injury or damage.
(b) The danger to life and property due to flooding or erosion damage.
(c) The susceptibility of the proposed development, including contents, to flood damage and the effect of such damage on current and future owners.
(d) The importance of the services provided by the proposed development to the community.
(e) The availability of alternate locations for the proposed development that are not subject to flooding or erosion.
(f) The compatibility of the proposed development with existing and anticipated development.
(g) The relationship of the proposed development to the comprehensive plan and flood plain management program for that area.
(h) The safety of access to the property in times of flood for ordinary and emergency vehicles.
(i) 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.
(j) 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.
(7) Conditions for issuance. Variances shall only be issued by the City Council upon:
(a) a technical showing of good and sufficient cause based on the unique characteristics of the size, configuration or topography of the site;
(b) a determination that failure to grant the variance would result in exceptional hardship by rendering the lot undevelopable;
(c) 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;
(d) a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief; and
(e) notification to the applicant in writing over the signature of the building official that the issuance of a variance to construct a structure below the base flood level will result in increased premium rates for flood insurance, and that such construction below the base flood level increases risks to life and property.
(G) Subdivisions.
(1) General. 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:
(a) all such proposals are consistent with the need to minimize flood damage;
(b) all public utilities and facilities, such as sewer, gas, electric and water systems are located and constructed to minimize or eliminate flood damage; and
(c) adequate drainage is provided to reduce exposure to flood hazards.
(2) Subdivision requirements. 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:
(a) The flood hazard area, including floodways, as appropriate, shall be delineated on tentative and final subdivision plats.
(b) Design flood elevations shall be shown on tentative and final subdivision plats.
(c) Residential building lots shall be provided with adequate buildable area outside the flood hazard area.
(d) The design criteria for utilities and facilities set forth in this section, Section 25-12-53 (Flood Loads), ASCE 24, the City of Austin Drainage Criteria Manual, and applicable FEMA design criteria shall be met.
(H) Site Improvement.
(1) Development in floodways. Development or land disturbing activity shall not be authorized in the floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed and sealed by a Professional Engineer licensed by the State of Texas in accordance with the City of Austin Drainage Criteria Manual, that the proposed encroachment will not result in any increase in the level of the design flood.
(2) Sewer facilities. 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.
(3) Water facilities. All new 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.
(4) Storm drainage. Storm drainage shall be designed to convey the flow of surface waters to minimize or eliminate damage to persons or property.
(5) Streets and sidewalks. Streets and sidewalks shall be designed to minimize potential for increasing or aggravating flood levels.
(I) Manufactured Homes.
(1) Elevation.
(a) All new and replacement manufactured homes to be placed or substantially improved in a flood hazard area shall be elevated such that the lowest floor of the manufactured home is elevated to a minimum of two feet above the design flood elevation. Elevation certification required by Section 25-12-53(D) (Flood hazard documentation) shall be submitted to the building official.
(b) The bottom of the frame of new and replacement manufactured homes on foundations that conform to the requirements of Section 25-12-53(C)(1) (Elevation Requirements), as applicable, shall be elevated to or above the elevations specified in Section 25-12-53(C)(1) (Elevation Requirements). The anchor and tie-down requirements of the applicable state or federal requirements shall apply. The foundation and anchorage of manufactured homes to be located in identified floodways shall be designed and constructed in accordance with ASCE 24.
(2) Foundations. 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 25-12-53 (Flood Loads).
(3) Anchoring. All new and replacement manufactured homes to be placed or substantially improved in a flood hazard area shall be installed using methods and practices which 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.
(4) Protection of mechanical equipment and outside appliances. Mechanical equipment and outside appliances shall be elevated a minimum of two foot above the design flood elevation to or above the design flood elevation.
Exception: Where such equipment and appliances are designed and installed to prevent water from entering or accumulating within their components and the systems are constructed to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding up to the elevation required by Section 25-12-53(C)(1) (Elevation Requirements), the systems and equipment shall be permitted to be located below the elevation required by 25-12-53(C)(1) (Elevation Requirements). Electrical wiring systems shall be permitted below the design flood elevation provided they conform to the provisions of NFPA 70.
(5) Enclosures. Fully enclosed areas below elevated manufactured homes shall comply with the requirements of 25-12-53(C) (Design and Construction).
(J) Recreational Vehicles.
(1) Placement prohibited. The placement of recreational vehicles shall not be authorized in floodways.
(2) Temporary placement. Recreational vehicles in flood hazard areas shall be fully licensed and ready for highway use; and shall be placed on a site for less than 180 consecutive days.
(3) Permanent placement. 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 Subsection (I) (Manufactured Homes) for manufactured homes.
(K) Tanks. Underground and above-ground tanks shall be designed, constructed, installed and anchored in accordance with ASCE 24.
(L) Foundation design and construction. This subsection applies to a building or structure subject to Article 11 (Residential Code).
(1) A foundation wall in a building or structure erected in a flood hazard area shall meet the requirements in Residential Code, Chapter 4 (Foundations).
Exceptions: Unless designed consistent with Residential Code, Section R404 (Foundation and Retaining Walls):
(a) the unsupported height of a 6-inch (152 mm) plain masonry wall shall not exceed 3 feet (914 mm);
(b) the unsupported height of an 8-inch (203 mm) plain masonry wall shall not exceed 4 feet (1219 mm); and
(c) the unsupported height of an 8-inch (203 mm) reinforced masonry wall shall not exceed 8 feet (2438 mm).
(2) For purposes of the exception in subsection (1), unsupported height is measured from the finished grade of the under-floor space to the top of the wall.
(Ord. No. 20210603-059, Pt. 4, 9-1-21)
