Article V Floodplain Regulations

Division 51A-5.100.  Flood Plain Regulations.

SEC. 51A-5.101.     DEFINITIONS AND INTERPRETATIONS APPLICABLE TO THE FLOOD PLAIN REGULATIONS.
     (a)     Definitions.  The following definitions are applicable to the flood plain regulations in this article:

          (1)     AREA OF SPECIAL FLOOD HAZARD means the land in the flood plain 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 having its floor subgrade, or below ground level, on all sides.

          (3)     BASE FLOOD means the flood having a one percent chance of being equalled or exceeded in any given year.

          (4)     DESIGN FLOOD (City’s Design Standard) means the 100-year frequency flood discharge as calculated for fully developed watershed conditions. For the Dallas Floodway Levee System, the design flood is the standard project flood as calculated for the Corridor Development Certificate process.

          (5)     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.

          (6)     ENVIRONMENTALLY SIGNIFICANT AREA means an area in the flood plain:

               (A)     with slopes greater than three to one;

               (B)     containing endangered species of either flora or fauna;

               (C)     which is geologically similar to the Escarpment Zone, as defined in Division 51A-5.200, "Escarpment Regulations," of this article;

               (D)     identified as wetlands; 

               (E)     determined to be an  archeological or historic site; or

               (F)     containing more than 1,000 square inches of trunk area of protected trees, in the aggregate, within a 10,000 square foot land area.  Trunk diameter is measured at a point 12 inches above grade. To be included in the calculation of trunk area, a tree must have a trunk equal to or greater than six inches.  For purposes of this subparagraph, a protected tree is defined in Section 51A-10.101 of this chapter.

          (7)     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.

          (8)     FEMA means the Federal Emergency Management Agency, which is the federal agency responsible for administering the National Flood Insurance Program.

          (9)     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.

          (10)     FLOOD INSURANCE RATE MAP (FIRM) means an official map of a community on which the Federal Emergency Management Agency has delineated the areas of special flood hazards and the insurance risk premium zones applicable to the community.

          (11)     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.

          (12)     FLOOD PLAIN (FP) means any land area susceptible to inundation by the design flood.

          (13)     FLOOD PLAIN ALTERATION means the construction of buildings or other structures, alterations, mining, dredging, filling, grading, or excavation in the flood plain which does not remove an FP designation. (Examples include the construction of a tennis court, a playground, a swimming pool, a fence, a deck, an erosion control wall, or the installation of significant landscaping.)

          (14)     FLOOD  PLAIN  OR  FP ADMINISTRATOR means the director of public works and transportation, who is responsible for administering the federal flood insurance program.

          (15)     FLOOD PROOFING means any combination of structural and non-structural additions, changes, or adjustments to structures which reduce or eliminate flood damage.

          (16)     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 or to discharge more than a designated height or rate.

          (17)     HUNDRED  YEAR  FREQUENCY FLOOD (100 year flood) means the flood having a one percent chance of being equalled 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.

          (18)     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.

          (19)     LEVEE  SYSTEM  means a flood protection system consisting of a levee or levees and associated structures such as closure and drainage devices constructed and operated in accordance with sound engineering practices.

          (20)     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.

          (21)     MANUFACTURED HOME means a structure, transportable in one or more sections, which 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 180 consecutive days, but does not include recreational vehicles.

          (22)     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.

          (23)     NATIONAL FLOOD INSURANCE PROGRAM (NFIP) means the federal program administered by FEMA which enables property owners to purchase flood insurance against damage to or loss of property resulting from a flood.

          (24)     POOL-RIFFLE SEQUENCES mean the alternating deep and shallow flow conditions caused by a moving, nonuniform channel grade.

          (25)     SEEP means a location where natural groundwater makes its way in a non-continuous flow to the surface, creating a wet soil condition.

          (26)     SPECIAL EXCEPTION means a grant of relief to a property owner permitting reconstruction in a manner otherwise prohibited by this division.

          (27)     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.

          (28)     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.

          (29)     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.

          (30)     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 by the local code enforcement official as necessary to assure safe living conditions, or any alteration of a structure listed on the National Register of Historic Places or a state inventory of historic places.

          (31)     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.

          (32)     SWALES mean low lying areas in the flood plain that convey flood waters when flow exceeds channel capacity.

          (33)     VALLEY STORAGE means the measure of a stream’s ability to store water as it moves downstream.

          (34)     VARIANCE means a grant of relief by a community from the terms of a flood plain management regulation.

          (35)     WATER  SURFACE  ELEVATION means the height, in relation to the National Geodetic Vertical Datum (NGVD) of 1929, of floods of various magnitudes and frequencies in the flood plain.

     (b)     Interpretations.     The intent of this ordinance 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(d).  (Ord. Nos. 19455; 19786; 20360; 24085)

SEC. 51A-5.102.     DESIGNATION OR REMOVAL OF FP AREAS.
     (a)     In general.  A flood plain designation is not a zoning classification, but refers to a specific area subject to flooding.  When this designation is noted by an “FP” prefix on the official zoning district map, the area designated is referred to in this article as an FP area.  FP areas include those identified as areas of special flood hazards by the FEMA in the August 4, 2004 flood insurance study for Dallas, Texas, and officially designated as FP areas by the city council.

     (b)     Initiation.  The addition to or removal from the official zoning district map of an FP prefix may be initiated in the following ways:

          (1)     An owner of property located within an FP area may apply for the review of an FP designation based upon evidence of a mapping error provided by the owner.

          (2)     The director of public works and transportation may, on his or her own initiative, review the status of an FP designation.

          (3)     An owner of property located within an FP area may apply for a fill permit and removal of the FP prefix by following the procedure outlined in Section 51A-5.105.

     (c)     Engineering studies.  Hydraulic and hydrologic engineering studies or a field survey must support any change to an FP designation. The director may require core borings as part of his or her investigations under this subsection.

     (d)     Decision on designation. The director of public works and transportation shall make a final decision on whether to add or remove an FP prefix on the official zoning district map only after the director determines that engineering studies support the change in the FP designation.

     (e)     Notice.

          (1)     Notice to adjacent municipalities.  At least 15 days before any final decision is made by the director of public works and transportation to add or remove an FP designation involving the alteration of a natural watercourse from the official zoning district map, the FP administrator shall notify any municipalities with property adjacent to the watercourse of the proposed change.

          (2)     Newspaper notice.  At least 15 days before notice to the director of development services pursuant to Subsection (f), the city secretary shall give notice of any change to the FP designation in the official newspaper of the city. Removal of the FP prefix shall become effective immediately upon publication of the notice in the official newspaper.

     (f)     Zoning map revision.  The director of public works and transportation must notify the director of development services in writing that an  FP prefix is to be removed from or added to the official zoning district map.  The written notification must contain a description of the property affected and the reasons why the FP prefix is being changed.  The director of public works and transportation shall keep a copy of the notification in a permanent file and send a copy of the notification to the city secretary, who shall keep the copy in a permanent file.

     (g)     Letter of Map Revision (LOMR). A letter of map revision from FEMA is required for removal of an FP prefix from the official zoning map if the area is designated as a flood hazard area on the FIRM. (Ord. Nos. 19455; 19786; 21299; 22920; 24085; 25047; 25716)

SEC. 51A-5.103.     COMPLIANCE IN UNDESIGNATED FLOOD PLAIN AREAS.
     (a)     A person shall comply with the requirements of this article for FP areas before developing land within the design flood line of a creek or stream having a contributing drainage area of 130 acres or more, even if the land has not been formally designated as an FP area.

     (b)     Alterations of the natural flood plain in areas with less than 130 acres must be approved by the director of public works and transportation for compliance with the Dallas Development Code and city drainage standards.  (Ord. Nos. 19455; 19786; 24085)

SEC. 51A-5.103.1.     VEGETATION ALTERATION IN FLOOD PLAIN PROHIBITED.

     (a)     A person commits an offense if he removes or injures any vegetation within a flood plain.

     (b)     It is a defense to prosecution under Subsection (a) if the act is:

          (1)     authorized in advance in writing by the director of public works and transportation;

          (2)     in conformance with a landscape plan approved by the director of public works and transportation;

          (3)     routine maintenance of vegetation such as trimming or cutting designed to maintain the healthy or attractive growth of the vegetation; or

          (4)     routine maintenance performed, required, or authorized by the city in order to maintain the floodwater conveyance capacity of the flood plain.  (Ord. Nos. 19455; 19786; 24085)

SEC. 51A-5.104.     USES AND IMPROVEMENTS PERMITTED.
 Not included here...

SEC. 51A-5.105.     FILLING IN THE FLOOD PLAIN.
     (a)     Permit required.

          (1)     A person shall not deposit or store fill, place a structure, excavate, or engage in any other development activities in an FP area without first obtaining:

               (A)     a fill permit or an FP alteration permit from the director of public works and transportation; and

               (B)     all other permits required by county, state, and federal agencies. 

          (2)     A fill permit allows the property to be developed at a specified elevation in compliance with this section.

          (3)     The director of public works and transportation shall maintain a record of all fill permits and FP alteration permits.

     (b)     Flood plain alteration permit. The director of public works and transportation may issue a flood plain alteration permit if he or she determines that:

          (1)     the alteration does not remove an FP designation; and

          (2)     the alteration complies with all applicable engineering requirements in Subsection (g).

     (c)     Initiation of fill permit process.  

          (1)     Application. An applicant for a fill permit shall submit an application to the director of public works and transportation on a form approved by the director and signed by all owners of the property.

          (2)     Notification signs.  An applicant is responsible for obtaining the required number of notification signs and posting them on the property that is subject of the application. Notification signs must be obtained from the director of public works and transportation at the time the application is made.

               
               (A) Number of signs required.  For tracts of five acres or less, only one notification sign is required. An additional notification sign is required for each additional five acres or less, except that no applicant is required to obtain and post more than five notification signs on the property, regardless of its size.

               (B) Posting of signs.  The applicant shall post the required number of notification signs on the property at least 15 days before the date of the scheduled public hearing before the city council. The signs must be posted at a prominent location adjacent to a public street and be easily visible from the street.

               (C)  Failure to comply.  If the city council determines that the applicant has failed to comply with the provisions of this section, it may postpone the public hearing.

     (d)     Preapplication conference.

          (1)     An applicant for a fill permit shall request a preapplication conference with representatives from the department of public works and transportation.

          (2)     At the preapplication conference, the director of public works and transportation shall determine what information is necessary for a complete evaluation of the proposed fill project.  The director may require the applicant to submit all necessary information, including, but not limited to the following:

               (A)     A vicinity map.

               (B)     The acreage figures for the entire tract, the area located in the flood plain, and the area proposed to be filled.

               (C)     A description of existing and proposed hydrologic and hydraulic analysis conducted.

               (D)     A landscape and erosion control plan.  The landscape plan must comply with the Landscape and Tree Preservation Regulations in Article X of the Dallas Development Code, as amended.

               (E)     A table of values for analysis of the engineering criteria listed in Subsections (g)(1), (g)(2), and (g)(4).

               (F)     A water surface profile.

               (G)     A plan view showing existing and proposed contours and grading.

               (H)     Plotted cross-sections.

               (I)     An overall map of the project area.

     (e)     Filling to remove an FP designation.

          (1)     Review of application by departments.  

               (A)     If the application is to remove an FP designation, the director of public works and transportation shall forward copies of the application to the director of development services and the director of park and recreation for review.

               (B)     The director of development services and the director of park and recreation shall review the application and advise the director of public works and transportation of the environmental impacts of the project. They shall also determine whether the applicant’s property should be considered for public acquisition due to its ecological, scenic, historic or recreational value. The director of public works and transportation shall provide a report to the city council on each application regarding environmental impacts and public acquisition issues.

          (2)     Neighborhood meeting.  The public works and transportation department shall schedule and conduct a neighborhood meeting on each application. The applicant or the applicant’s representative must attend the neighborhood meeting. The director shall send written notice of the meeting to the applicant, to all owners of real property within 500 feet from the boundary of the subject property, and to persons and organizations on the early notification list on file with the department of development services. Measurements include the streets and alleys. The notice must be given not less than 10 days before the date set for the neighborhood meeting by depositing the notice properly addressed and postage paid in the United States mail to the property owners as evidenced by the last approved city tax roll. This notice must be written in English and Spanish if the area of request is located wholly or partly within a census tract in which 50 percent or more of the inhabitants are persons of Spanish origin or descent according to the most recent federal decennial census.

          (3)     Notice and public hearing.  After the neighborhood meeting, the director of public works and transportation shall schedule a public hearing on the application. The city secretary shall give notice of the public hearing in the official newspaper of the city at least 15 days before the date of the public hearing. The director shall also send written notice of the public hearing to the applicant, to all owners of real property within 500 feet from the boundary of the subject property, and to persons and organizations on the early notification list on file with the department of development services. Written notice must be given in the same manner required in Paragraph (2) for the neighborhood meeting.

          (4)     Decision on application.

               (A)      After notice and a public hearing in compliance with Paragraph (3), the city council shall approve or deny the application for a fillpermit. The city council may only deny an application if:

                    (i)   the application does not meet the requirements of Section 51A-5.105(g); or

                    (ii)     the city council has, by resolution, authorized acquisition of the property under the laws of eminent domain, and denial of the application is necessary to preserve the status quo until the property is acquired.

               (B)     In connection with its approval of a fill permit, the city council may grant a variance to the requirements of Subsection (g) if the variance will not violate any provision of federal or state law or endanger life or property.

               (C)     If the city council approves a fill permit application, the FP designation for the filled area may be removed from the official zoning district map upon compliance by the applicant with the specifications for filling.

          (5)     Zoning map revision.  Upon compliance with all applicable requirements of this section by the applicant, the director of public works and transportation shall notify the director of development services, who shall remove the FP designation for the filled area from the official zoning district map.

          (6)     Letter of Map Revision (LOMR).  A letter of map revision must be obtained from FEMA, if applicable, before an FP prefix may be removed from the official zoning district map.  A building permit may be issued for construction of underground utilities if a conditional letter of map revision (CLOMR) is obtained; however, no building permit for construction of a structure may be issued until a final letter of map revision (LOMR) is obtained.

     (f)     Filling operations.  If the city council approves a fill permit, the filling operations must comply with the following requirements:

          (1)     Any excavation required by the specifications of the approved application must be conducted before or at the same time as placing fill.

          (2)     Building pad sites must be filled to an elevation of at least two feet above the design flood elevation.

          (3)     The lowest floor of any structure must be constructed at least three feet above the design flood elevation.

          (4)     Fill material must consist of natural material including but not limited to soil, rock, gravel, or broken concrete.  Decomposable matter, including but not limited to lumber, sheetrock, trees, tires, refuse, or hazardous, toxic matter, is prohibited as fill material.  Fill must be compacted to 95 percent standard proctor density.

          (5)     Before construction, erosion control devices such as straw hay bales, silt fences or similar items must be installed to eliminate any transportation of sediment downstream.  The property owner is responsible for removal of any sediment deposited by runoff as a result of filling.

          (6)     If compliance with a National Pollutant Discharge Elimination System (NPDES) permit is required for construction activities, a copy of the Notice of Intent (NOI) or the individual NPDES permit must be submitted to the director of public works and transportation before beginning fill operations.

          (7)     Fill shall be placed no more than five feet above the design flood elevation, except where necessary to match the existing elevation of the adjacent property as determined by the director of public works and transportation.  In determining when it is necessary to match the existing elevation, the director shall consider the effects on local drainage and storm water management, the access needs of the property, and other public health and safety concerns.

          (8)     A copy of the approved fill permit must be posted and maintained at the fill site for inspection purposes until fill operations have been completed.

          (9)     After filling operations have been completed, the applicant shall submit a certification to the director of public works and transportation that proper fill elevations, compaction requirements, and all other specifications of the approved application have been followed. In addition, the applicant shall submit a copy of the letter of map revision (LOMR) issued by FEMA, if applicable.

     (g)     Engineering requirements for filling.

          (1)     Except for detention basins, alterations of the FP area may not increase the water surface elevation of the design flood of the creek upstream, downstream, or through the project area.  Detention basins may increase the water surface elevation of the design flood provided the increase is within the detention basin's boundaries as approved by the director of public works and transportation.

          (2)     Alterations of the FP area may not create or increase an erosive water velocity on or off-site.  The mean velocity of stream flow at the downstream end of the site after fill may not exceed the mean velocity of the stream flow under existing conditions.

          (3)     The effects of the existing and proposed public and private improvements will be used in determining water surface elevations and velocities.

          (4)     The FP area may be altered only to the extent permitted by equal conveyance reduction on both sides of the natural channel. The following valley storage requirements apply to all FP areas except those governed by a city council-adopted management plan that contains valley storage regulations, in which event the valley storage regulations contained in the plan apply:

               (A)     Except as otherwise provided in Subparagraph (B):

                    (i)     no loss of valley storage is permitted along a stream with a drainage area of three square miles or more;

                    (ii)     valley storage losses along streams with a drainage area between 130 acres and three square miles may not exceed 15 percent, as calculated on a site by site basis; and

                    (iii)     valley storage losses along streams with a drainage area of less than 130 acres is not limited.

               (B)     Hydrologic computations may be performed to evaluate basin-wide valley storage loss impacts on the design flood discharge. If the computations demonstrate that valley storage losses do not result in increases in the design flood discharge at any point downstream of the project, valley storage losses are permitted even though they exceed the limits provided in Subparagraph (A).

          (5)     An environmental impact study and a complete stream rehabilitation program must be approved before relocation or alteration of the natural channel or alteration of an environmentally significant area. The net environmental impacts of the proposal may not be negative. The environmental impact study must contain the following items.

               (A)     A description of the existing conditions of the site, adjacent properties, upstream and downstream creek sections for approximately 1,000 feet (unless conditions require additional information in the opinion of the director of public works and transportation), and creek and overbank areas. The description of these conditions must include:

                    (i)     the characterization of creek features such as bed quality and material, pool-riffle sequences, natural ground water, springs, seeps, magnitude and continuity of flow, water quality (including biological oxygen demand, dissolved oxygen, and nutrient loadings), bank quality and material, vegetative cover and patterns, bank erosion, topographic relief, disturbances to the natural character of the creek, animal and aquatic life, and the extent and character of wetland areas; and

                    (ii)     soil types and land uses of the site and surrounding area.

               (B)     A description of the proposed project.  This description must include:

                    (i)     the intended ultimate use of the site, or if that is not known, a description of the interim site plan, including construction access;

                    (ii)     reasons why the creek or flood plain alteration is necessary; and

                    (iii)     a site plan showing the flood plain and construction access necessary to perform the work.

               (C)     A description of at least three possible ways of handling the creek and flood plain, including:

                    (i)     an alternative that assumes the creek and flood plain are not changed;

                    (ii)     the applicant’s proposed action; and

                    (iii)     alternatives proposed by the director of public works and transportation.

               (D)     An identification of the impacts created by each alternative, describing in detail all of the positive and negative impacts upon the existing conditions described in Subparagraph (A), that would be created by each alternative.

               (E)     A recommended course of action based upon evaluation of  the alternatives.

               (F)     Proposed strategies to mitigate adverse impacts. Examples of strategies include tree wells, temporary construction and permanent erosion and sedimentation controls, vegetative buffers, and replacement planting.

          (6)     The toe of any fill slope must parallel the natural channel to prevent an unbalanced stream flow in the altered FP area.

          (7)     To insure maximum accessibility to the FP area for maintenance and other purposes and to lessen the probability of slope erosion during periods of high water, maximum slopes of the filled area may not exceed four to one for 50 percent of the length of the fill and six to one for the remaining length of the fill.  The slope of any excavated area may not exceed four to one unless the excavation is in rock. Vertical walls, terracing, and other slope treatments may be used provided no unbalancing of stream flow results and the slope treatment is approved as a part of a landscaping plan for the property.

          (8)     The elevation of excavated areas in the FP area may not be lower than one-third of the depth of the natural channel, as measured from the adjacent bank, except for excavation of lakes. Excavation must be at least 50 feet from the bank of  the natural channel, except as necessary to provide proper drainage.  The excavated area may not exceed 25 percent of the total area of the tract’s unfilled flood plain.

          (9)     A landscape and erosion control plan must be submitted and approved. Landscaping must incorporate natural materials (such as earth, stone, and wood) on cut and filled slopes when possible. The definitions of Section 51A-10.101 of this chapter apply to this subsection. Except as otherwise provided, the preservation and mitigation requirements contained in the tree preservation regulations, Division 51A-10.130 of the Dallas Development Code, apply. Each landscape and erosion control plan must comply with the following criteria:

               (A)     The size, type, and location of all trees within the existing flood plain that are six-inch caliper and larger must be shown. The plans must indicate which of the trees are to be preserved and which will be lost due to development activities in the flood plain.

               (B)     Trees must be protected if they are more than six-inches in caliper and located in sloped areas of flood plain fill with a depth of four feet or less.  If trees are protected by tree wells, the wells must be at or beyond the drip line of the tree and must provide positive drainage. A well may not exceed four feet in depth unless designed and certified by a registered landscape architect.  Tree wells are required if either of the following conditions occur at the base of a tree to be protected:

                    (i)     a fill of greater than six inches; or

                    (ii)     a cut greater than six inches.

               (C)     The size, type, and location of all proposed replacement trees to mitigate the loss of existing trees must be shown.  The tree types must be selected in accordance with the provisions of Section 51A-10.134 and must be approved by the city arborist as suitable for use under local climate and soil conditions.

               (D)     Where a swale is proposed, tree replacement is required for the loss of existing trees with a six-inch caliper or greater located within the proposed swale.  The applicant must indicate replacement of either 35 percent of the number of trees displaced, or the minimum number of trees necessary to provide a spacing equivalent to 50 feet on center, whichever is less.  At least 50 percent of the replacement trees must have a caliper of at least six inches.  The remainder of the trees must have a caliper of at least three inches.

               (E)     The specific plant materials proposed to protect fill and excavated slopes must be indicated.  Plant materials must be suitable for use under local climate and soil conditions.  In general, hydroseeding or sodding Bermuda grass is acceptable during the summer months (May 1st to August 30th). Winter rye or fescue grass may be planted during times other than the summer months as a temporary measure until such time as the permanent planting can be accomplished.

               (F)     The proposed methods of erosion and sedimentation control, such as hay bales and sedimentation basins, to be used during construction must be shown in detail.

               (G)     The fill case applicant, current owners, and subsequent owners must maintain and assure the survival of all planted material until the property is developed and a permanent maintenance plan of record is established.  Maintenance responsibility must be reflected in the submitted plans or supporting documents.

          (10)     Any alteration of the FP area necessary to obtain a removal of an FP prefix may not cause any additional expense in any current or projected public improvements.

     (h)     Special criteria for the Trinity and the Elm Fork.  If the FP area is in the flood plain of the Trinity River, Elm Fork of Trinity River, West Fork of the Trinity River, Five Mile Creek - confluence to Bonnie View Road, White Rock Creek - confluence to Scyene Road, or the regulatory floodways established by FEMA, the following requirements must be met:

               (A)     Encroachment into the floodway is prohibited unless FEMA issues a conditional Letter of Map Revision.

               (B)     Fill elevations and first floor elevations in flood plain areas located along the Elm Fork, West Fork or main stem of the Trinity River that would be protected from inundation by the 100-year or greater flood by a federally authorized flood control project must be constructed at a minimum elevation of one foot above the design flood.  The parking requirements in Section 51A-5.104(b)(4) do not apply.

     (i)     Term of permit validity and extension procedures.

               (A)     Permits issued after October 11, 1996.     A fill permit is valid for a five-year time period from the date of issuance.  The fill permit automatically terminates if the filling operations have not been completed within the five-year time period. The director of public works and transportation may grant a one-time extension of a fill permit for an additional three-year time period upon receipt of a written request made at least 30 days before the expiration of the original permit. The applicant for permit extension must demonstrate that the project fully complies with the flood plain regulations that were in effect at the time that the original permit was approved.

               (B)     Permits issued before October 11, 1996.  Fill permits issued before October 11, 1996, shall expire on December 31, 2001. The director of public works and transportation shall notify owners of fill permits governed by this paragraph that:

                    (i)     filling must be completed no later than December 31, 2001; and 

                    (ii)     a one-time extension of the permit for an additional three-year time period may be granted by the director of public works and transportation upon receipt of a written request made at least 30 days before the expiration date of the original permit.  The applicant for permit extension must demonstrate that the project fully complies with the flood plain regulations that were in effect at the time that the original permit was approved.

               (C)     New permit required upon expiration.  When a fill permit terminates, the applicant must apply for a new permit before filling the property. The new application must comply with the flood plain regulations that are in effect at the time that the request is considered by the city council.

               (D)     Presumption of completion.  Filling operations are deemed completed when the applicant submits:

                    (i)     a certification to the director of public works and transportation that proper fill elevations have been achieved and the specifications of the approved application have been followed; and 

                    (ii)     a letter of map revision from FEMA, if applicable.  (Ord. Nos. 19455; 19786; 21299; 22920; 24085; 25047)

SEC. 51A-5.106.     SETBACK FROM NATURAL CHANNEL REQUIRED.
     (a)     For purposes of this section:

          (1)     NATURAL CHANNEL SETBACK LINE means that setback line described below located the farther beyond the crest:

               (A)     That line formed by the intersection of the surface of the land and the vertical plane located a horizontal distance of 20 feet beyond the crest.

               (B)     That line formed by the intersection of the surface of the land beyond the crest and a plane passing through the toe and extending upward and outward from the channel at the designated slope.  For purposes of this paragraph, the designated slope is:

                    (i)     four to one if the channel contains clay or shale soil; and

                    (ii)     three to one in all other cases.

          (2)     CREST means that line at the top of the bank where the slope becomes less than four to one.

          (3)     TOE means that line at the bottom of the bank where the slope becomes less than four to one.

     (b)     Except as otherwise provided in Subsection (c), all structures must be located behind the natural channel setback line.

     (c)     A structurally engineered retention system approved by the director of development services may be substituted for the setback required in Subsection (b).  (Ord. Nos. 19786; 24085)

SEC. 51A-5.107.     TRINITY RIVER CORRIDOR DEVELOPMENT CERTIFICATE PROCESS.
     (a)     Definitions.  In this section:

          (1)     CORRIDOR  DEVELOPMENT CERTIFICATE (CDC) MANUAL means the manual by that title dated January 31, 1992, or its latest revision, which is attached to this ordinance and kept on file in the office of the city secretary.

          (2)     FLOOD PLAIN ALTERATION means any construction of buildings or other structures, mining, dredging, filling, grading, or excavation in the floodplain.

          (3)     TRINITY RIVER CORRIDOR means the portion of the flood plain of the West Fork, Elm Fork, and mainstream segments of the Trinity River flood plain within the Dallas city limits, as delineated on the latest CDC Regulatory Map.

     (b)     Certificate required.  A person commits an offense if he makes any flood plain alteration within the Trinity River Corridor without first obtaining a corridor development certificate from the director of public works and transportation.  It is a defense to prosecution that an exemption or variance has been obtained in accordance with CDC criteria.

     (c)     Application.  An application for a corridor development certificate must be filed with the director of public works and transportation on a form furnished by the department of public works and transportation.

     (d)     Review.  The director of public works and transportation shall deny an application for a certificate unless it complies with the standards contained in the CDC Manual or unless an exemption from or variance to those standards is obtained in accordance with Subsection (e) of this section.

     (e)     Exemptions and variances.

          (1)     Exemptions.

               (A)     An exemption from the requirements of this section may be obtained if the floodplain alteration involves the following activities:

                    (i)     Ordinary maintenance of and repair to flood control structures.

                    (ii)     The construction of outfall structures and associated intake structures if the outfall has been permitted under state or federal law.

                    (iii)     Discharge of material for backfill or bedding for utility lines, provided there is no significant change in pre-existing bottom contours and excess materials are removed to an upland disposal area.

                    (iv)     Bank stabilization.

                    (v)     Any project listed in the U.S. Army Corps of Engineers March 1990 Reconnaissance Report, which is attached as Appendix A to the CDC Manual, or any project approved under the provisions of this division, provided the approval, permit, or authorization has not expired and no significant changes have occurred since the approval, permit, or authorization was issued.

               (B)     Application for an exemption must be made to the director of public works and transportation on a form provided by the department of public works and transportation.

               (C)     If the director of public works and transportation determines that an application for an exemption falls within one of the categories listed in Paragraph (1), the director shall issue a written exemption from the requirements of this section.

          (2)     Variances. If the director of public works and transportation determines that the application for a corridor development certificate does not comply with all of the standards contained in the CDC Manual, the applicant may apply for a variance to any standard contained in the manual.  An application for a variance must be made to the director of public works and transportation, who shall schedule the application for consideration by the city council.  (Ord. Nos. 21636; 24085)


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