(a) Definitions. The following definitions are applicable to the floodplain regulations in this article:
(1) AREA OF SPECIAL FLOOD HAZARD means the land in the floodplain within a community that is subject to a one percent or greater chance of flooding in any given year.
(2) BASEMENT means any area of a building, including any sunken room or sunken portion of a room, having its floor below ground level (subgrade) on all sides.
(3) BASE FLOOD means the flood event having a one percent chance of being equaled or exceeded in any given year.
(4) BASE FLOOD ELEVATION means the water surface elevation from a flood event having a one percent chance of being equaled or exceeded in any given year, which is shown on the flood insurance rate map (FIRM) and in the accompanying flood insurance study (FIS) for Zones A, AE, AH, A1 - A30, AR, V1-V30, or VE, or on the regulatory floodplain maps.
(5) DESIGN FLOOD (City's Design Standard) means the 100-year frequency (one percent chance of being equaled or exceeded in any given year) flood discharge as calculated for fully developed watershed conditions.
(6) DEVELOPMENT means any manmade change in improved and unimproved real estate, including but not limited to the construction of buildings or other structures, mining, dredging, filling, grading, paving, excavation, drilling operations, or storage of equipment or materials unless approved by the city on a temporary basis in connection with authorized construction activities.
(7) ENVIRONMENTALLY SIGNIFICANT AREA means an area in the floodplain:
(A) containing endangered species of either flora or fauna;
(B) which is a geologically similar area, as defined in Division 51A-5.200, "Escarpment Regulations," of this article;
(C) identified as wetlands or waters of the United States; or
(D) determined to be an archaeological or historic site.
(8) EQUAL CONVEYANCE REDUCTION means the ability of the property on the opposite side of the stream to construct a project that alters conveyance by the same amount as the proposed fill permit or floodplain alteration permit project.
(9) EXISTING MANUFACTURED HOME PARK means a manufactured home park or subdivision for which the construction of facilities for servicing the lots was completed before March 16, 1983, the effective FIRM date.
(10) FEDERAL EMERGENCY MANAGEMENT AGENCY (FEMA) means the federal agency responsible for administering the National Flood Insurance Program (NFIP).
(11) FILL PERMIT means the process of reclaiming a portion of land in the floodplain to create a developable area including but not limited to a habitable structure or parking area, raising any area of land out of a floodplain area on fill, or creating an area that can be developed in the future. The fill permit process removes the floodplain (FP) designation and is applicable in areas with an upstream drainage area greater than 100 acres, even if the land has not been formally designated as an FP area.
(12) FIVE HUNDRED YEAR FREQUENCY FLOOD (500-YEAR FLOOD) or 0.2 PERCENT ANNUAL CHANCE EXCEEDANCE PROBABILITY FLOOD EVENT means the flood event having a 0.2 percent chance of being equaled or exceeded in any given year. The 500-year flood in Dallas is based upon fully developed land uses within the watershed as defined by the current zoning designation.
(13) FLOOD OR FLOODING means a general and temporary condition of partial or complete inundation of normally dry land areas from the unusual and rapid accumulation or runoff of surface waters from any source.
(14) FLOOD INSURANCE RATE MAP (FIRM) means an official map of a community on which the Federal Emergency Management Agency (FEMA) has delineated the areas of special flood hazards and the insurance risk premium zones applicable to the community.
(15) FLOOD INSURANCE STUDY (FIS) means the official report provided by FEMA containing flood profiles, water surface elevation of the base flood, and the Flood Boundary-Floodway Map.
(16) FLOODPLAIN (FP) means any land area susceptible to inundation by the design flood, even if the land has not been formally designated as an FP area on the Regulatory Floodplain Maps.
(17) FLOODPLAIN ALTERATION means the construction of uninhabitable structures, alterations to existing structures within a floodplain area complying with Section 51A-5.104(b), mining, dredging, filling, grading, or excavation in the floodplain that does not remove or alter an FP designation. (Examples include, but are not limited to, the construction of a tennis court, a playground, a gazebo, a swimming pool, a fence, a deck, an erosion control wall, or the installation of significant landscaping.)
(18) FLOODPLAIN OR FP ADMINISTRATOR means the director of water utilities, who is responsible for administering the federal flood insurance program, or the director's designated representative.
(19) FLOODPROOFING means any combination of structural and non-structural additions, changes, or adjustments to structures that reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, or structures and their contents. If floodproofing is utilized, the design must be certified by a licensed professional engineer.
(20) FLOODWAY (OR 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 design flood without cumulatively increasing the water surface elevation more than a designated height.
(21) FLOODWAY EASEMENT means a drainage area dedicated to the city as an easement to prevent obstructions of floodway capacity in a floodplain.
(22) FUNCTIONALLY DEPENDENT USE means a use that cannot perform its intended purpose unless it is located or carried out in close proximity to water. This term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and shipbuilding and ship repair facilities, but does not include long-term storage or related manufacturing facilities.
(23) HABITABLE STRUCTURE means any structure with electric, heat, or plumbing that can be used for living, sleeping, eating, or assembly purposes.
(24) HIGHER STANDARDS means community requirements that exceed the minimum FEMA standards for participating in the National Flood Insurance Program (NFIP).
(25) INTERIOR DRAINAGE AREAS means the geographical areas that act as a watershed for the sumps.
(26) LETTER OF MAP CHANGE (LOMC) means a letter that reflects an official change in an effective Flood Insurance Rate Map (FIRM). LOMCs are issued in response to a request to FEMA to revise or amend its effective flood map to remove a property or reflect changed flooding conditions on the effective map and can include Letter of Map Revisions (LOMRs), Letter of Map Amendments (LOMAs), and Letter of Map Revisions based on Fill (LOMR-F's) as amended by FEMA.
(27) LEVEE means a manmade structure (usually an earthen embankment) designed and constructed in accordance with sound engineering practices to contain, control, or divert the flow of water for protection from temporary flooding.
(28) LEVEE SYSTEM means a flood protection system consisting of a levee or levees and associated structures accredited by FEMA pursuant to 44 CFR 65, as amended, such as closure and drainage devices constructed and operated in accordance with sound engineering practices.
(29) LICENSED PROFESSIONAL ENGINEER means a person who is duly licensed and registered to engage in the practice of engineering in the State of Texas in accordance with state law.
(30) LOWEST ADJACENT GRADE means the lowest point of the ground level immediately next to a building.
(31) LOWEST FLOOR means the lowest floor of the lowest enclosed area of a building (including its basement). An unfinished or flood resistant enclosure that is useable 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.
(32) MANUFACTURED HOME means a structure, transportable in one or more sections, that is built on a permanent chassis and designed for use with or without a permanent foundation when connected to the required utilities. In this article only, the term "manufactured home" includes park trailers, travel trailers, and similar vehicles placed on a site for more than 90 consecutive days, but does not include recreational vehicles.
(33) MANUFACTURED HOME PARK OR SUBDIVISION means a parcel (or contiguous parcels) of land divided into two or more manufactured home lots for rent or sale.
(34) NATIONAL FLOOD INSURANCE PROGRAM (NFIP) means the federal program administered by FEMA that enables property owners to purchase flood insurance against damage to or loss of property resulting from a flood.
(35) ONE HUNDRED YEAR FREQUENCY FLOOD (100-year flood) or ONE-PERCENT ANNUAL CHANCE EXCEEDANCE PROBABILITY FLOOD EVENT means the flood event having a one percent chance of being equaled or exceeded in any given year. The 100-year flood in Dallas is based upon fully developed land uses within the watershed as defined by the current zoning designation.
(36) POOL-RIFFLE SEQUENCES mean the alternating deep and shallow flow conditions caused by a moving, nonuniform channel grade.
(37) REGULATORY FLOODPLAIN MAPS means the most updated floodplain maps available, as accepted by the City of Dallas, regardless of adoption by FEMA. These include, but are not limited to, maps resulting from floodplain update studies, Letter of Map Revisions (LOMRs), and floodplain studies resulting from current and proposed construction projects.
(38) SEEP means a location where natural groundwater makes its way in a non-continuous flow to the surface, creating a wet soil condition.
(39) SPECIAL EXCEPTION means a grant of relief to a property owner permitting reconstruction in a manner otherwise prohibited by this division.
(40) STANDARD PROJECT FLOOD means the flood caused by the most severe combination of meteorological and hydrological conditions reasonably characteristic of the region. The standard project flood is defined by the U.S. Army Corps of Engineers for use in major flood control projects.
(41) STRUCTURE means, for purposes of this division, a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.
(42) 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 50 percent of the market value of the structure before the damage occurred.
(43) SUBSTANTIAL IMPROVEMENT means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50 percent of the market or tax appraisal value of the structure, whichever is greater, as determined by an independent appraiser or the last official City tax roll, either before the improvement or repair is started, or, if the structure has been damaged and is being restored, before the damage occurred. For the purpose of this definition "substantial improvement" occurs when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure. The term does not, however, include any project for improvement of a structure for the sole purpose of complying with federal, state, or local health, sanitary, or safety code specifications which have been identified in writing by the local code enforcement official as necessary to assure safe living conditions prior to the start of the proposed improvement, or any alteration of a historic structure as defined by FEMA. See Section 51A-5.104(b)(2) for city of Dallas limitations.
(44) SUMPS mean drainage features of levee systems that temporarily store storm water runoff before it is conveyed to a river system by pumping over or draining through a levee.
(45) SWALES mean low lying areas in the floodplain that convey flood waters when flow exceeds channel capacity.
(46) VALLEY STORAGE means the measure of a stream's ability to store water as it moves downstream.
(47) VARIANCE means a grant of relief by a community from the terms of a floodplain management regulation.
(48) WATER SURFACE ELEVATION means the height, in relation to the North American Vertical Datum (NAVD), of floods of various magnitudes and frequencies in the floodplain.
(b) Interpretations. The intent of this division is to equal or exceed the minimum federal criteria for participation in the National Flood Insurance Program, located in 44 Code of Federal Regulations, Chapter I, Part 60.3, as amended; and FEMA 480, as amended. All higher standards and FEMA minimum standards apply. The City of Dallas must also enforce any more restrictive state requirements. The City of Dallas has exceeded the minimum standards by adopting more comprehensive floodplain management regulations. In some instances, community officials may have access to information or knowledge of conditions that require, particularly for human safety, higher standards than the minimum NFIP criteria. Any floodplain management regulations adopted by a state or community that are more restrictive than the criteria set forth in the NFIP regulations take precedence. All FEMA minimum standards in the Code of Federal Regulations also apply. (Ord. Nos. 19455; 19786; 20360; 24085; 27318; 27572; 27697; 27893; 30994; 31314; 32039)