Sec. 35-F106. - Special Floodplain Definitions.
Unless specifically defined below, words or phrases used in this ordinance shall be interpreted to give them the meaning they have in common usage and to give this ordinance its most reasonable application. The following definitions apply only to this ordinance:
1% annual chance floodplain (formerly 100-year floodplain) is the land within a community subject to a one (1) percent or greater chance of flooding in any given year. These areas are typically designated as a Federal Emergency Management Agency (FEMA) Zone A, AE, AH, or AO on FEMA Flood Insurance Rate Maps (FIRM Panels). May also be referred to as the FEMA effective floodplain.
Alluvial fan flooding means flooding occurring on the surface of an alluvial fan or similar landform which originates at the apex and is characterized by high-velocity flows; active processes of erosion, sediment transport, and deposition; and unpredictable flow paths.
Apex means a point on an alluvial fan or similar landform below which the flow path of the major stream that formed the fan becomes unpredictable and alluvial fan flooding can occur.
Appurtenant structure means a structure which is on the same parcel of property as the principal structure to be insured and the use of which is incidental to the use of the principal structure.
Area of flood inundation refers to sites that are subject to flooding as a result of water ponding in the controlled storage areas of dams, detention and retention ponds.
Area of future flood conditions means the land area that would be inundated by the 1% annual chance (100-year) flood based on future conditions hydrology.
Area of shallow flooding means a designated AO, AH, AR/AO, AR/AH, or VO zone on a community's Flood Insurance Rate Map (FIRM) with a one (1) percent or greater annual chance of flooding to an average depth of one (1) to three (3) feet where a clearly defined channel does not exist, where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow.
Area of special flood hazard is the land in the floodplain within a community subject to a one (1) percent or greater chance of flooding in any given year. The area may be designated as Zone A on the Flood Hazard Boundary Map (FHBM). After detailed rate making has been completed in preparation for publication of the FIRM, Zone A usually is refined into Zones A, AO, AH, A1-30, AE, A99, AR, AR/A1-30, AR/AE, AR/AO, AR/AH, AR/A, VO, V1-30, VE or V.
Base flood means the flood having a one (1) percent chance of being equaled or exceeded in any given year.
Base flood elevation (BFE) means the elevation shown on the Flood Insurance Rate Map (FIRM) and found in the accompanying Flood Insurance Study (FIS) for Zones A, AE, AH, A1-A30, AR, V1-V30, or VE that indicates the water surface elevation resulting from the flood that has a 1% chance of equaling or exceeding that level in any given year - also called the base flood.
Basement means any area of the building having its floor subgrade (below ground level) on all sides.
Breakaway wall means a wall that is not part of the structural support of the building and is intended through its design and construction to collapse under specific lateral loading forces, without causing damage to the elevated portion of the building or supporting foundation system.
CLOMR means a Conditional Letter of Map Revision. A CLOMR will be submitted for FEMA approval for all proposed physical changes to the floodplain that will result in a change to the floodplain boundary.
Critical feature means an integral and readily identifiable part of a flood protection system, without which the flood protection provided by the entire system would be compromised.
Development means any manmade change in improved and unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or, drilling operations or storage of equipment or materials. Capital improvement projects where the grade or ground is disturbed or modified within the project limits to construct proposed improvements will be considered development.
Ecological functioning: The fundamental ecological services that floodplain, riparian areas or Streamside Management Zone (SMZ) areas perform. Ecological services include but are not limited to: assist in mitigating nonpoint source pollution; stabilize stream banks and reduce floodwater velocity resulting in reduced erosion and downstream flood peaks; maintain water levels in streams, lakes, water tables and aquifers; sequester greenhouse gases to improve air quality; and supply food, cover and water for a diversity of terrestrial and aquatic wildlife especially migratory birds.
Elevated building means a non-basement building (i) built, in the case of a building in Zones AE, A, A99, AO, AH, X, and D, to have the top of the elevated floor, elevated above the ground level by means of pilings, columns (posts and piers), or shear walls parallel to the floor of the water and (ii) adequately anchored so as not to impair the structural integrity of the building during a flood of up to the magnitude of the base flood. In the case of Zones AE, A, A99, AO, AH, X, D, "elevated building" also includes a building elevated by means of fill or solid foundation perimeter walls with openings sufficient to facilitate the unimpeded movement of floodwater s.
Existing construction means, for the purposes of determining rates, structures for which the "start of construction" commenced before the effective date of the FIRM or before January 1, 1975, for FIRMs effective before the date. "Existing construction" may also be referred to as "existing structures."
Existing manufactured home park or subdivision means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including, at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed before the effective date of the floodplain management regulations adopted by a community.
Expansion to an existing manufactured home park or subdivision means the preparation of additional sites by the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads).
FEMA Effective Floodplain see 1% annual chance floodplain.
Flood or flooding means a general and temporary condition of partial or complete inundation of normally dry land areas from:
(1) The overflow of inland or tidal waters.
(2) The unusual and rapid accumulation or runoff of surface waters from any source.
Flood elevation study means an examination, evaluation and determination of flood hazards and, if appropriate, corresponding water surface elevations, or an examination, evaluation and determination of mudslide (i.e., mudflow) and/or flood-related erosion hazards.
Flood Insurance Rate Map (FIRM) means an official map of a community, on which the Federal Emergency Management Agency has delineated both the special flood hazard areas and the risk premium zones applicable to the community.
Flood Insurance Study (FIS) is the official report provided by the Federal Emergency Management Agency. The report contains flood profiles, water surface elevation or the base flood, as well as the flood boundary map. Also see Flood Elevation Study.
Floodplain means any land area susceptible to being inundated by water from any source (see definition of flooding).
Flood-prone area means any land area susceptible to being inundated by water from any source (see definition of flooding).
Floodplain management means the operation of an overall program of corrective and preventive measures for reducing flood damage, including but not limited to emergency preparedness plans, flood control works and floodplain management regulations.
Floodplain management regulations means zoning ordinances, subdivision regulations, building codes, health regulations, special purpose ordinances (such as a floodplain ordinance, grading ordinance and erosion control ordinance) and other applications of police power. The term describes such state or local regulations, in any combination thereof, which provide standards for the purpose of flood damage prevention and reduction.
Flood protection system means those physical structural works for which funds have been authorized, appropriated, and expended and which have been constructed specifically to modify flooding in order to reduce the extent of the area within a community subject to a "special flood hazard" and the extent of the depths of associated flooding. Such a system typically includes hurricane tidal barriers, dams, reservoirs, levees or dikes. These specialized flood modifying works are those constructed in conformance with sound engineering standards.
Floodproofing means any combination of structural and non-structural additions, changes, or adjustments to structures which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents.
Floodway see Regulatory Floodway.
Functionally dependent use means a use, which cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and ship building and ship repair facilities, but does not include long-term storage or related manufacturing facilities.
Green infrastructure or nature-based storm water management: an approach to storm water management that protects, restores, or mimics the natural water cycle and enhances community safety and quality of life.
Habitable structure means a structure that has facilities to accommodate people for an overnight stay. These include, but are not limited to, residential homes, apartments, condominiums, hotels, motels, and manufactured homes. Recreational vehicles are not included in this definition.
Highest adjacent grade means the highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.
Historic structure means any structure that is:
(1) Listed individually in the National Register of Historic Places (a listing maintained by the Department of Interior) or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;
(2) Certified or preliminarily determined by the Secretary of the Interior as contributing to the historical significance of a registered historic district or a district preliminarily determined by the Secretary to qualify as a registered historic district;
(3) Individually listed on a state inventory of historic places in states with historic preservation programs which have been approved by the Secretary of the Interior; or
(4) Individually listed on a local inventory or historic places in communities with historic preservation programs that have been certified either:
(a) By an approved state program as determined by the Secretary of the Interior or;
(b) Directly by the Secretary of the Interior in states without approved programs.
Levee means a man-made structure; usually an earthen embankment, designed and constructed in accordance with sound engineering practices to contain, control, or divert the flow of water so as to provide protection from temporary flooding.
Levee system means a flood protection system which consists of a levee, or levees, and associated structures, such as closure and drainage devices, which are constructed and operated in accordance with sound engineering practices.
LOMR means a letter of map revision. A LOMR will be submitted for FEMA approval for all changes to the floodplain boundary that are delineated on the current Flood Insurance Rate Maps.
Low Water Crossing: a vehicular roadway crossing, including public or private driveways, that may provide access during low flow storm events and to be periodically overtopped during higher flow storm events.
Lowest floor means the lowest floor of the lowest enclosed area (including basement). An unfinished or flood resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other than a basement area is not considered a building's lowest floor; provided that such enclosure is not built so as to render the structure in violation of the applicable non-elevation design requirement of Section 60.3 of the National Flood Insurance Program regulations.
Manufactured home means a structure transportable in one (1) or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when connected to the required utilities. The term "manufactured home" does not include a "recreational vehicle".
Manufactured home park or subdivision means a parcel (or contiguous parcels) of land divided into two (2) or more manufactured home lots for rent or sale.
Mean sea level means, for purposes of the National Flood Insurance Program, the North American Vertical Datum (NAVD) of 1988 or other datum, to which base flood elevations shown on a community's Flood Insurance Rate Map are referenced.
Natural state means the topography that exists at the time information is gathered for flood insurance rate maps or any subsequent approved revisions to those maps.
New construction means, for the purpose of determining insurance rates, structures for which the "start of construction" commenced on or after the effective date of an initial FIRM or after December 31, 1974, whichever is later, and includes any subsequent improvements to such structures. For floodplain management purposes, "new construction" means structures for which the "start of construction" commenced on or after the effective date of a floodplain management regulation adopted by a community and includes any subsequent improvements to such structures.
New manufactured home park or subdivision means a manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed on or after the effective date of floodplain management regulations adopted by a community.
Recreational vehicle means a vehicle which is (i) built on a single chassis; (ii) four hundred (400) square feet or less when measured at the largest horizontal projections; (iii) designed to be self-propelled or permanently towable by a light duty truck; and (iv) designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel, or seasonal use.
Regulatory floodplain is the land within the community subject to a one (1) percent or greater chance of flooding in any given year assuming all future development has occurred throughout the watershed. The regulatory floodplain is delineated on the currently effective FEMA Flood Insurance Rate Maps (FIRM Panels). NOTE: As the city's floodplain ordinance (this Appendix F of the Unified Development Code) is approved by FEMA as a condition of participation in the National Flood Insurance Program (NFIP), the city's regulatory floodplain is considered FEMA's future base flood. Regulatory floodplain may also be referred to as the City of San Antonio (CoSA) ultimate conditions floodplain.
Regulatory floodway means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. The floodway is congruent with the regulatory 1% annual chance floodplain in the City of San Antonio and its Extra Territorial Jurisdiction.
Repetitive loss means flood-related damages sustained by a structure on two (2) separate occasions during a ten-year period for which the cost of repairs at the time of each such flood event, on the average, equals or exceeds twenty-five (25) percent of the market value of the structure before the damage occurred.
Riparian areas: Riparian areas are lands that occur along watercourses and water bodies. Typical examples include flood plains and streambanks. They are distinctly different from surrounding lands because of unique soil and vegetation characteristics that are strongly influenced by the presence of water.
Riverine means relating to, formed by, or resembling a river (including tributaries), stream, brook, etc.
Special flood hazard area see Area of Special Flood Hazard.
Start of construction means for all new construction and substantial improvements, the date the building permit was issued, provided the actual start of construction, repair, reconstruction, rehabilitation, addition placement, or other improvement was within one hundred eighty (180) days of the permit date. The actual start means either the first placement of permanent construction of a structure on a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation; or the placement of a manufactured home on a foundation. Permanent construction includes land preparation, such as clearing, grading and filling; includes the installation of streets and/or walkways; excavation for a basement, footings, piers or foundations or the erection of temporary forms; the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or not part of the main structure. The start of construction period is valid for one hundred eighty (180) days. Any delay beyond this period would require resubmission of added data and the permit application. For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor, or other structural part of a building, whether or not that alteration affects the external dimensions of the building.
Structure means, for floodplain management purposes, a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.
Substantial damage means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed fifty (50) percent of the market value of the structure before the damage occurred. Substantial damage also means flood-related damages sustained by a structure on two (2) separate occasions during a ten-year period for which the cost of repairs at the time of each such flood event, on the average, equals or exceeds twenty-five (25) percent of the market value of the structure before the damage occurred.
Substantial improvement means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds fifty (50) percent of the market value of the structure before "start of construction" of the improvement. This includes "substantial damage", regardless of the structures which have incurred "repetitive loss" or actual repair work performed. The term does not, however, include either:
(1) Any structure's continued designation as a "historic structure" project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary conditions or
(2) Any alteration of a "historic structure", provided that the alteration will not preclude the structures continued designation as a "historical structure."
Tributary: a river, creek, or stream that feeds into a larger stream or river and are sites of intrinsic ecological value where particular biophysical processes and ecosystem services may be concentrated. In addition, they play a crucial role on downstream channel morphology.
Ultimate conditions base flood elevation (BFE) means the water surface elevation resulting from the flood that has a 1% chance of equaling or exceeding that level, assuming future conditions hydrology.
Unflooded access means that vehicular traffic has safe access (within the "Proceed with Caution" range per figure 4.3.1C of Appendix H) to a property from a public street in times of a design storm event (reference Appendix H 4.3.2) and to an arterial street that is not adjacent to the development or to a distance of one-quarter mile, whichever is less, during a twenty (20) percent annual chance (20% A.C., or "5-year") storm event.
Variance is a grant of relief from the requirement of this chapter when specific enforcement would result in unnecessary hardship. A variance, therefore, permits construction or development in a manner otherwise prohibited by this subdivision. (For full requirements see Section 60.6 of the National Flood Insurance Program regulations.)
Violation means the failure of a structure or other development to be fully compliant with the community's floodplain management regulations. A structure or other development without the elevation certificate, other certifications, or other evidence of compliance required in 44 CFR Section 60.3 (Floodplain management criteria for flood-prone areas) is presumed to be in violation until such time as that documentation is provided.
Water surface elevation means the height, in relation to the North American Vertical Datum (NAVD) of 1988 (or other datum, where specified), of floods of various magnitudes and frequencies in the floodplains of coastal or riverine areas.
(Ord. No. 95415 § 1 Attachment A) (Ord. No. 2009-01-15-0001, § 2, 1-15-09) (Ord. No. 2010-05-06-0376, § 4, 5-6-10) (Ord. No. 2010-10-14-0894, § 2, 10-14-10) (Ord. No. 2010-11-18-0985, § 2, 11-18-10; Ord. No. 2022-11-03-0831, § 2, 11-3-22, eff. 1-1-23)
