O1RROILTON STORMWATER AND : i , .. , ; FLOOD PROTECTION ORDINANCE FEBRUARY 1994 NATHAN D. MAIER CONSUl..TING ENGINEERS. INC, DaHas. Tella& (214:) 139-4141 
RH'D APR 1 81997 QlRROI&TON April 17, 1997 Mr. John Baumgartner, City Engineer Town ofAddison P.O. Box 144 Addison, TX 75001 Re: Addison Drainage Contribution Dear Mr. Baumgartner: The
City of Carrollton has experienced considerable erosion and flooding problems within our city in the past. Due to these problems, the City of Carrollton has requested that neighboring
cities and towns require developments, within drainage basins that discharge to and pass through the City of Carrollton, comply with the City of Carrollton Stormwater and Flood Protection
Ordinance. We are enclosing a copy of this ordinance for your files. Presently, both the City ofDallas and the City ofPlano require that any development, whose drainage flows through
the City of Carrollton, submit drainage plans to the City of Carrollton and obtain a letter stating that the development appears to conform to this ordinance. We are requesting your
assistance in this area by asking that the City of Addison join with the cities ofDallas and Plano in requiring the same type ofreview and approval of drainage plans on sites contributing
to the drainage flow through Carrollton. Please respond in writing as to your consent to this request. Ifyou should have any questions concerning the ordinance, or our request, feel
free to contact us. Sincerely, 􀁾􀁾􀀠/Joe Evans Division ManagerlDesign cc: File Tim Tumulty, City Engineer ENGINEERING • 1945 E. Jackson Road· P.O. Box 110535 • Carrollton, Texas 75011·0535.972/466·
3200. Fax: 972/466·3193 
I ORDINANCE NO. ....;2",,2,-,-1:=..8___ AN ORDINANCE OF THE CITY OF CARROLLTON, TEXAS AMENDING THE REVISED STORMW ATER AND FLOOD PROTECTION ORDINANCE REGULATING DEVELOPMENT WITHIN THE
CITY TO PROVIDE FOR ELEVATION CERTIFICATES, DETENTION AND RETENTION FACILITIES AND NON-RESIDENTIAL CONSTRUCTION; PROVIDING FOR A PENALTY FOR NON-COMPLIANCE; SEVERABILITY AND PROVIDING
AN EFFECTIVE DATE WHEREAS, the original Stormwater and Flood Protection Ordinance No. 1375 for the City of Carrollton was adopted by the City Council on May 12, 1987; and revised on
February 15, 1994 (Ordinance 1964); and WHEREAS, certain revisions of the Stormwater and Flood Protection Ordinance are necessary to promote orderly development ofthe city. NOW, THEREFORE,
BE IT ORDAINED BY THE COUNCIL OF THE CITY OF CARROLLTON,TEXAS: Section 1. That the "Stormwater and Flood Protection Ordinance", Article 4, Section C (permits), Subsection 4 (Elevation
Certificate) is hereby amended and shall read in its entirety as follows: Developers, owners or builders shall complete an elevation certificate prior to issuance of a Certificate of
Occupancy by the City whenever a development and/or building is constructed in a designated floodplain area. Section 2. That the "Stormwater and Flood Protection Ordinance", Article
7, Section D (Detention and Retention Facilities), Subsection 2 is hereby amended and shall read in its entirety as follows: Detention areas in parking lots shall not be: In required
parking spaces except as provided in Section D(7). Behind speed bumps unless the speed bumps are made with reinforced concrete. Deeper than six inched unless warning signs are posted.
! i I I 
Ordinance No. 2218 Page 2 Section 3. That the "Stormwater and Flood Protection Ordinance," Article 7, Section D (Detention and Retention Facilities) is hereby amended to add subsection
7 which shall read in its entirety as follows: 7. Detention facilities will be allowed in the parking areas of commercial and/or industrial uses. Section 4. That the "Stormwater and
Flood Protection Ordinance", Article 8, Section B (General Floodplain Regulations), Subsection 3 (Non-residential Construction) is hereby amended and shall read in its entirety as follows:
New construction in reclaimed floodplain areas and "substantial improvement" of any existing commercial, industrial, or other non-residential structure in floodplain areas shall either
have the lowest floor, including basements ofany new or "substantial improvement" construction, elevated to at least two feet above the design flood elevation; or, together with attendant
utility and sanitary facilities, shall: Be floodproofed so that below two feet above the design flood elevation, the structure is watertight, with walls, substantially impermeable to
the passage ofwater; Have structural components capable ofresisting hydrostatic and hydrodynamic loads and effects of buo yancy; and Be certified by a registered professional engineer
or architect that the standards of this subsection are satisfied. Such certifications shall be provided to the official set forth in Article 4, Section AI. Incremental improvements,
either at one time or over a period of time, the cumulative cost of which equals or exceeds 50 percent of the market value at the time of the first improvement, shall be considered as
a "substantial improvement." Improvements to an existing commercial, industrial or other non-residential structure that increase the outside dimensions, but do not result in a "substantial
improvement," must meet the requirements of Article S.C. Parking lot pavement for the truck loading docks may be constructed below the design flood elevation. Table 10 presents a synopsis
ofthe requirements for nomesidential structures in floodplain areas. 
Ordinance No. 2218 Page 3 Section S. That save and except as amended by this ordinance, Ordinance No. 1964 adopting the Storm water and Flood Protection Ordinance, shall remain ill full
force and effect. Section 6. That conviction of a violation of the S tormwater and Flood Protection Ordinance is punishable in accordance with Section 10.99 of the Carrollton City Code.
Section 7. That the provisions oftrus ordinance are severable in accordance with Section 10.07 of the Carrollton City Code. Section 8. That this ordinance shall be effective from and
after the date of passage. PASSED AND APPROVED THIS ISm DAY OF OCTOBER 1996. Pamela Schmidt City Secretary Q V) 7A 􀁾􀀠;PO '\<V APPROVED AS TO FORM: 􀁾􀁌􀁔􀁏􀁾􀀬􀀠􀀧􀀱􀁦􀁴􀀺􀀺􀀬􀁾 City
Attorney APPROVED AS TO CONTENT: -.,...---􀁬􀁫􀀼􀁾􀀠􀁾􀀠Timothy M. Tumblty, P.E. City Engineer . ': 
-.1 STORMWATER AND FLOOD PROTECTION· ORDINANCE FEBRUARY 1994 
ORDINANCE NO. 1964 CODIFIED AS CHAP1ER 174 OF THE CARROllTON CITY CODE OF ORDINANCES INDEX ARTICLE I -TI1LE, FINDINGS OF FACT, STATEMENT OF PURPOSE, SCOPE OF AUTHORITY, AND PENALTY FOR
NON-COMPLIANCE Section A. Tide. • . . . . . • . • . . . . • • • . . . . • • • • • • • • • • . . . . . • • . • • . • .1 Section D. Scope of Authority. • • • • . • . . • . • • • • • .
. . • • • • • . • . • . . • . . • • • J. Section E. Organization ofThis Ordinance . • . . . . . • • . . . . . • • • • • . • . . . • • • . . J. Section B. Findings of Fact. • • • • •
. . . . • . . • . . . . . • • . . . . . • • • . • • . . • • • .1 Section C. Statement of Purpose. • . . . . . . • . • . . • • . . . . . • . . • • . . • . . . • • . . .1 Section F. Related
Ordinances . • • • • • • • • . . . . • • • . • . . . . • • . . • • . • • . . • . .3 ARTICLE 2 • DEFlNlTIONS • • • • . . . . . . • • • • • • . . . • . . . . . . • • • . . . . . • . .
.4 ARTICLE 3 GENERAL PROVISIONS Section A. Lands to Which This Ordinance Applies. . • • • • • • • . . . . • . • • • • • . . . • . • 15 Section B. Basis for Establishing the Areas ofSpecial
Flood Hazard. . . . . • • . . • . . . . ••• 15 Section C. Penalty Clause. • • • • • • . . . • • . • • • . • . . . . • • • • • • . • • • • . • • • • 15 Section D. Repealing Clause • •
• • . . . . . • . . • . . . . . . • • • • • • . . • . . • . . • . . 15 Section E. Abrogation and Greater Restrictions. . . • • . • • • • • • • . . . . . . . • • • . • . . 15 Section
F. Interpretation • . . . . • • • • • . . . . • • • . • . . • • • • . . . . . • • . • • . . . 16 Section G. Waming and Disclaimer ofLiability •..•..••.•...••.••••.••.••• 16 Section H.
Severability • . . • . . • . . • • . • • . • • • • • . • . . . . . . . • . . . . . . • • . 16 ARTICLE 4 ADMINISTRATION Section A. Duties of City Officials •. . . • • • . . . . . . .
. • • • . • • • . . • . . • . . . . . 17 Section B. Responsibilities of Owners. • . . . . . . . . . • . . . • • . . . • • • • • . • . • . . . 17 Section C. Pexmits • . • . . . . . .
. . • . . • . . • . . • • . . . . • . . • . • . . . . . . . . . 18 Section D. Plan Requirements. . . • • . • • . • • . • • • • . . . • . • . . • • • • • . . • . . • . 20 Section E. Maintenance
Bonds . . • . • • • • • • • . . . • • • . • . • • . • • • • . . . . . • . . 24 Section F. Appeals and Variance Procedure••.••......••.•.....••.......25 ARTICLE 5 RUNOFF CALCULATIONS
Section A. Procedure for Drainage Areas Less Than 160 Acres . . . • • . • • • • • . . . . . . . . 27 Section B. Procedure for Drainage Areas Greater Than 160 Acres. . • • . . • • . .
. . • • . • • • 29 ARTICLE 6 • DESIGN OF LOCAL DRAINAGE SYSTEMS Section A. Design Stoxm Frequencies. • . . . • . . . . . . . . . . . . • . • . . • • • . . . • • • 30 Section B. Street
and Alley Capacities. . . • • . . • • . . • . . • • • • • • • . . . • . . • . • . . 30 Section C. Placement ofIniets. . . . • . . . . . . • • . . . • . . . . • • . • . . • . . • . .
• . • 31 Section D. Inlet Capacities and Sizes • • . . . . . . • . . • . • • . . . . • • • • . • • . . . . . . 31 
Section E. Pipe Design Standards. • • • • . . • • . • . • • • • • • . • • • • . . • . • • • • • . • 31 Section F. Culvert Design Standards . . • • • . . . • . . • • • • . . • • • • •
. . . • • • • • • . 36 ARTICLE 7 -SPECIAL DRAINAGE FACILITIES Section A. Channels. • . . . • • . .-. • . . • • . . . . • . • • • . • . . . • . • . . . . . . • . • 37 Section B. ,Lakes
and Darns. . . . . . • • • . • . . . . . • • • • . . . . • • . • • . . • • • . • • 39 Section C. Levees. . . • • • • • . . . . • • • • • • . . . • . . • • • . • . • • • . . • . • . .
. . 42 Section D. Detention and Relention Facilities. • . . • • • • • . . . • . • . . . . . • • • . . . . .43 Section E. Flumes........ • • • • • . . • . . . • . . . • • • • • • • •
. . . • . . • • . . •44 Section F. Connections from Buildings to Storm Sewers. . • • • • . . . . • • • • • . . . . • • . .44 ARTICLE & -FLOODPLAIN GUIDELINES Section A. Lands to Which
This Article Applies •...••••.••.••••••....•.•.•45 Section B. General Floodplain Regulations • • . . • . . . . • . • • • • . . . . . • • • • . . • • • .45 Section C. Floodplain Alterations.
• • . . . . • . • • . . . • • • . . • . . • . . • • • • . . . • .49 Section D. Verification of Floodplain Alterations • • • . . . . . • • • • . . . . • . . . • . • . . . 50 ARTICLE 9
CORRIDOR DEVELOPMENT CERTIFICATE PROCESS Section A. Trinity River Corridor Interlocal Agreement. • . • • • • • • • . • • • • • . • • • • . . 51 Section B. Trinity River Corridor Aree
• • . . • • . • • . • . • • • • • • • • • • • • • • . • • • • 51 Section C. EslabIishment of Deyelopment Permit. . • . • • • • . . • • • • • • . . . . • . . • • . 51 Section D. Duties
and Responsibilities of the Floodplain Administrator . • • • • • . . . • . . • • • 52 Section E. Common Permit Criteria. . . . . • • . . . . . . . • • . . . . . . . • • . . . . . . .
. 52 Section F. Exemptions from Corridor Development Certificale (CDC). . . . . . . • • • . . • . . . 52 Section G. Approval Process • . . • • • . . . . . . • • • . . . . • • • • . .
. . • • • • . . • •• 53 53 Section H. Appeals Process. . . . . . . . . . . . . • . . . . . . . . . . • . . . . . . • . . • . . 53 Section I. Technical Updales. • • . . . • • • • • .
. . . • . • . . . . • . • • . • . . . . • • . • 53 Section J. CDC Manual . . • • • • . . . • • . • . . . . • • • • • . • . • • • . • • • • • . . . . 53 ARTICLE 10 STORM WATER DISCHARGES
FROM CONSTRUCTION ACTIVITlES Section A. General Requirements. • • • • . • • • • . . . • . • • • • . • . • • • • • . • • • • . 55 Section B. Five-Acre Disturbances • • • . . • • • • .
• • • • • . • • . • • • . . • . • • • • • . 57 ii 
TABLES TABLE 1 -VALUES OF "C· FOR USE IN RATIONAL METHOD FORMULA Q= CIA. • • . . . . . . .60 TABLE 2 -AVERAGE VELOCITY FOR USE IN DE1ERMIN1NG TIME OF TABLE 9 -SUITABLE VEGETATION FOR
CHANNELS TABLE 10 -SYNOPSIS OF REQUIREMENTS TO PROTECT S1RUCTURES CONCENTRATION. • . . . . . . . . . . . . . . . . . • • . . . . • • . • • • • . • • . • • .61 TABLE 3 MINIMUM SLOPES
FOR CONCRE1E PIPES •••.•.•••....•....•••••• .61 TABLE 4 MAXIMUM VELOCITIES IN CONDUITS FLOWING FULL AND CHANNELS. • . • . • • .62 TABLE 5 -ROUGHNESS COEFFICIENTS FOR CLOSED CONDUITS
• . • • . • . • • • • . . . . . . .62 TABLE 6 -ENTRANCE LOSS COEFFICIENTS . • . . . . . • • • • • . • • . • . . • • . • . . . . . . .63 TABLE 7 -VELOCITY HEAD LOSS COEFFICIENTS FOR CLOSED
CONDUITS. . . • • . . . • • • . .64 TABLE 8 ROUGHNESS COEFFICIENTS FOR OPEN CHANNEL FLOW AREAS • • • • . . . . . . • .65 1EMPORARY VEGETATION . • • . • . • • • . • . • • • • • • • •
• • • . . . . . . • • • .67 PERMANENT VEGETATION -LOW AREAS • • • . . • . • • • • • • . • . • . • . • . . . • .68 PERMANENT VEGETATION· SIDE SLOPES •••...••...•...•.....••..69 PERMANENT
VEGETATION -BERMS, SPOIL BANKS, AND SIMILAR AREAS • . . . . .70 FROM FLOODING • • • • • • • • . . . • . • . . . . . . . . . . . • • • • . . . . . . . . . .72 TABLE 11 -PERMlSSIDLE VELOC1T1ES
FOR CHANNELS LINED WITH GRASS ••.•..••..•.76 ill 
1 FIGURES FIGURE 1 -CITY OF CARROllTON RAINFALL INTENSITY VALUES •.••••.•••..•••.77 FIGURE 2 -CAPACITY OF TRIANGULAR GUTI'ERS . . • . . . . . . . . . . . . • • • . . . • . • .78 FIGURE
3 CAPACITY OF PARABOLIC GUTI'ERS (26',31' & 36' STREET WIDTHS), •••••••.79 FIGURE 4 CAPACITY OF PARABOLIC GUTI'ERS (40' AND 44' STREET WIDTHS) ....•••. .80 FIGURES -CAPACITY OF AlLEY
SECTIONS • • • • • • . • . • • • • . • . . . . . . • • • • • • . .81 FIGURE 6 STORM DRAIN INLETS. . . • • • . . • • . • • . . . . . . . . . . . . • . • • • • • • . .82 FIGURE 7 -RECESSED
AND STANDARD CURB OPENING INLET CAPACITY CURVES ON GRADE (30' F-F S1REET WIDTH, S" PARABOLIC CROWN 36' F-F S1REETWIDTH, 6" PARABOLIC CROWN) • • . • • • • • • • . • • • • • • • • .84
FIGURE 8 RECESSED AND STANDARD CURB OPENING INLET CAPACITY CURVES ON GRADE (ALL S1REET WIDTHS. 1(1, INCH/FOOT CROSS SLOPE CROWN)•...•.....•.....••.•.•••.•.•....•.•.•. .85 FIGURE 9 -RECESSED
AND STANDARD CURB OPENING INLET CAPACITY CURVES ON GRADE (ALL S1REET WIDTHS. 1/4 INCH/FOOT CROSS SLOPE CROWN). . . . . . . . . . . . . . . • . • . • • . • • • • . . . • . • • . . . .
. .86 FIGURE 10 -RECESSED AND STANDARD CURB OPENING INLET CAPACITY CURVES ON GRADE (ALL S1REET WIDTHS, 318 INCH/FOOT CROSS SLOPE CROWN; 40' F-F STREET WIDTH, 6" PARABOLIC CROWN; 44'
F-F S1REET WIDTH. 6" PARABOLIC CROWN) • • . • . . • • • • • • . . . . . . • .87 FIGURE 11 -RECESSED AND STANDARD CURB OPENING INLET CAPACITY CURVES ON GRADE (ALL S1REET WIDTHS, 6" INVERTED
CROWN) • • . • • • • • .88 FIGURE 12 • RECESSED AND STANDARD CURB OPENING INLET CAPACITY CURVES AT LOW POINT (ALL S1REET WIDTHS. SlRAlGlIT AND PARABOLIC CROWN), . . . . . • • . . • •
• • . • • • • • • • . . . . . • • . . • • • • .89 FIGURE 13 TWO GRATE COMBINATION INLET CAPACITY CURVES ON GRADE. . . . . . . • .90 FIGURE 14 • THREE GRATE COMBINATION INLET CAPACITY
CURVES ON GRADE. . . • • • • 91 iv 
FIGURE 15 FOUR GRATE COMBINATION INLET CAPACITY CURVES ON GRADE. •••••.• !J2 FIGURE 16 COMBINATION INLET CAPACITY CURVES AT LOW POINT •••••.•.••..• 93 FIGURE 17 TWO GRATE INLET CAPACITY
CURVES ON GRADE .•.••..•••••..... 94 FIGURE 18 -POUR GRATE INLET CAPACITY CURVES ON GRADE......••••••••... 95 FIGURE 19 SIX GRATE INLET CAPACITY CURVES ON GRADE. . . . • . • . • • .
• • . • • • • 96 FIGURE 20 GRATE INLET CAPACITY CURVES AT LOW POINT. • • . • • . • . • . • • . • • • . 97 FIGURE 21 -DROP INLET CAPACITY CURVES AT LOW POINT.••••••••...•••..•• 98 FIGURE
22 CAPACITY OF CIRCULAR PIPES FLOWING FULL ..........•.•.••... 99 FIGURE 23 OUTFALL OF A STORM SEWER INTO A CHANNEL .•...•.••..•••••••100 FIGURE 24 APPROXIMATE ROUTING METHOD FOR WATERSHEDS
< 160 ACRES. • • • • • • • 101 FIGURE 25 NATURAL FLOODWAY EXAMPLE . • . . • • • . • • • . . . . • • • • • . . • • • • • 103 v 
ORDINANCE NO. 1964 ARTICLEl SECTION 1 TITLE. FINDINGS OF FACT, STATEMENT OF PURPOSE. AND SOOPEOF AUIHORITY 􀁏􀁒􀁇􀁾􀁔􀁉􀁏􀁎􀁑􀁆􀁔􀁉􀁗􀁓􀁏􀁒􀁄􀁾􀀠SECTION A. Title This Ordinance shall
be known as the "Stormwater and Flood Protection Ordinance" of the City of Carrollton. and shall consist of a one hundred-three (103) page document attacbed hereto and made a part of
this Ordinance. SECTION B. Findinrs ot Fact I. The drninage ways and flood hazard areas of the City of Carrollton. Texas, are subject to periodic inundation which may result in loss
of· life and property. health and safety hazards. disruption of commerce and governmental services, and extraordinary public expendimres for flood protection and relief, all of which
adversely affect the public health. safety. and general welfare. 2. These floed losses are created by the cumulative effect of obstructions in floodPlains that increase flood heights
and velocities and by the occupancy of flood hazard areas by uses vulnerable to floods and hazardous to other lands because they are inadequately elevated, flocdproofed. or otherwise
protected from flood damage, SECTION C. Stalfment ot Purpose This ordinance sets forth the minimum requirements necessary to provide and maintain a safe, efficient. and effective drninage
system within the City of Orrrollton and to establish the various public and private responsibilities for the provision thereof. Further, it is the purpose of this ordinance to: (I)
Protect human life. health. and property; (2) Minimize expenditure ofpublic money for drainage related projects; (3) Minimize damage due to drainage to public and private facilities
and utilities such as water and gas mains, electric service. telephone and sewer lines, streets and bridges; (4) Help maintain a stable tax base and preserve land values; (5) Insure
that potential buyers are notified that property is in an area of special flood hazard; (6) Insure that those who occupy the areas of special flood hazard assume responsibility for their
actions. (7) Preserve the natural beauty and aesthetics of the community. 1 
(8) Conlrol and manage all stormwater runoff and drainage from points and surfaces within subdivisions. (9) Establish a reasonable standard of design for development which prevents potential
flood and slormwater damage. SECTION D. Scope or Authority Except as exempted by Article 9. Section F. any person. finn. corporation. or business proposing to develop land or improve
property within the City of Carrollton is subject to the provisions of this ordinance. This ordinance also applies to individual building structures. SUbdivisions. excavations and fill
operations. and similar activities. The Scope of Authority extends to additional improvements on projects. developments. subdivisions. etc. which were previously permitted and/or constructed
under the authority of prior ordinances or guidelines. SECTION E. Organization of This Ordinance This ordinance revises the provisions of the former "Stormwater and Flood Protection
Ordinance" (Ordinance No. 1375) which combined the provisions of the former "Official Drainage and Stormwater Control Ordinance" (Ordinance No. 1051) and the "Flood Hazard Prevention
Ordinance' (Ordinance No. 905). Further. it expands and clarifies various aspects of these ordinances. The following list is a synopsis of the contents of each article. Article 1 -discusses
the purposes. scope, and authority of this ordinance, and provides a penalty for noncompliance with this ordinance. Article 2 -lists and defines various terms used in this ordinance.
Article 3 -states general provisions related to implementation and enforcement of this ordinance. Article 4 -overviews the administrative procedures to be followed for obtaining the
necessary City drainage approvals related to building on or improving property. Article 5 -explains the methodologies to calculate runoff quantities. Article 6 -gives the design standards
for building local drainage systems (ie.• enclosed storm sewers). Article 7 -states additional design standards for specialty drainage system items. Article 8· presents the floodplain
regnlations. including the requirements to be met when reclaiming floodplain land. Article 9· presents additional regulations for activities within the Regulatory Zone of the Elm Fork
Trinity River and tributaries. Article 10· provides requirements for controlling stann water runoff and associated erosion for construction activities. 2 
SECTION F. Related Ordinances In addition to this ordinance. the City of Carrollton has other ordinances. regulations, and specifications pertaining to drainage and storm sewer facilities.
These other docwnents include the zoning and subdivision ordinances. the Standard Specifications for Public Works Construction by the North Centrnl Texas Council of Governments as amended
by the City of Carrollton, and the General Design Standards for the City of Carrollton, and shall remain in full force and effect If there is any conillct between such prior ordinance
and this ordinance, this ordinance shall prevail. 3 
ARTICLE 2 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: 1. Angle of Flare Angle between direction of a wingwall and centerline ofculvert Or storm drainage outlet or inlet. 2. Appeal A request for
review or interpretation of any provisions of this ordinance or a request lbr a variance. 3. Area of Shallow Flooding A designated AO Or AH Zone on the Flood Insurance Rate Map (FIRM).
The base flood depths range from one to three feet; a clearly defined channel does not exist; and the path of flooding is unpredictable and indeterminate. 4. Area ofSpecial Flood Hazard
The land in the floodplain within a community subject to a one percent or greater chance of flooding in any given year. 5. Base Flood The flood having a one percent chance of being equalled
or exceeded in any given year, determined based upon FEMA guidelines and as shown in the current effective Flood Insurance Study. 6. Base Flood Elevation The water surface elevation
resulting from the base flood. 7. Best Management Practices (BMP) Consists of schedules of practices, maintenance procedures, and other management practices to prevent or reduce the
pollution of waters of the United States. This also includes treatment requirements, operating procedures, and practices to control construction site runoff, spillage or leaks, sludge
or waste disposal, or drainage from raw material storage. 8. City The City of Carrollton, Texas, or the City Council of Carrollton. 9. City Engineer The person appointed to the position
of City Engineer by the City Council of the City of Carrollton, or hislher duly authorized representative. 4 
10. Commencement of Construction The disturbance of soils associated with clearing. grading. or excavating activities or other construction activities. 11. Conduit Any closed device
for conveying flowing water. 12. Corridor Development Certificate A required permit process established for activities within the Regulatory Zone of the Trinity River and its tributaries.
13. Critical Feature An integral and readily identifiable part of a flood protection system, without which the flood protection provided by the entire system would be compromised. 14.
Design Flood The flood having a one percent chance of being equalled or exceeded in any given year based upon fully developed watershed conditions. 15. Detention Basin A dry basin or
depression constructed for the purpose of temporarily storing storm water runoff and discharging all of that water over time at a reduced rate than would have otherwise occurred. 16.
Developer/Builder A person, partnerShip, or corporation engaged in the development of land and/or building of structures and not excluded by exemption sections of this ordinance. 17.
Development Any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation.
drilling operations, grading. or clearing. 18. Director of Public Works The person appointed to the pOSition of Director of Public Works by the City Council of the aty of Carrollton,
or his/her duly authorized representative. 19. Discharge Any addition or introduction of any pollutant, storm water, or any other substance whatsoever Into the municipal separate storm
sewer system (MS4) or into waters of the United States. 20. Discharger Any person who causes, allows, permits, or is otherwise responsible for, a discharge, including, without limitation,
any operator of a construction site or industrial facility. 5 
21. Elevated Building In the case of Zones AI-30, A, A99, AO, B, C, D, VI-V30, and any other designated FEMA Zone, an "elevated building" includes a building elevated by means of fill
so that the finished floor of the building is at least two feet above the water surface elevation of the design flood. 22. Entrance Head The head required to cause flow into a conduit
or other structure; it includes both entrance loss and velocity head. 23. Entrance Loss Head lost in eddies or friction at the inlet to a conduit, headwall, or structure. 24. Environmental
Protection Agency (EPA) The United States Environmental Protection Agency, the regional office thereof, any federal department, agency, or commission that may succeed to the authority
of the EPA, any duly authorized official of EPA or such successor agency. 25. Equal Conveyance Principle of reducing stream conveyance for a proposed alteration with a corresponding
reduction in conveyance to the opposite bank of the stream. The right of equal conveyance applies to all owners and uses and may be relinquished only by written agreements. 26. Erosion
The wearing away of the land surface by running water, wind, ice, or other geological agents, including such processes as gravitational creep. In this manual, erosion due to storm water
runoff is the primary design issue. 27. Existing Construction For the purposes of determining rates, structures for which the "start of construction" commenced before the effective date
of Ordinance 905. "Existing construction" may also be referred to as "existing structures." 28. Facilitv Any building, structure, installation, process, or activity from which there
is or may be a discharge of pollutant. 29. Federal Emergency Management Agency (FEMA) Federal agency which administers National Flood Insurance Program. 30. Final Stabilization The status
when all soil disturbing activities at a site have been completed, and a uniform perennial vegetative cover with a density of 70% of the cover for unpaved areas and areas not covered
by permanent permanent structures has been established, or equivalent permanent stabilization measures (such as the use of riprap, gabions, or geotextiles) have been employed. 6 
31. Flood or Flooding A general and temporary condition of partial or complete inundation of normally dry land areas from: (1) The overflow of inland waters and/or (2) The unusual and
rapid accumulation or runoffofsurface waters from any source. 32. Flood Insurance Rate Map (FIRM) The official map on which the Federal Emergency Management Agency has delineated both
the areas of special flood hazards and the risk premium zones applicable to the community. 33. Flood Insurance Study The official report in which the Federal Emergency Management Agency
has provided flood profiles, the water surface elevation of the base flood, as well as the Flood Boundary-F1oodway Map. 34. Floodplain or Flood-prone Area Any land area susceptible to
being inundated by water from any source (see definition of flooding). 35. Flood Protection SYStem 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 areas 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. 36. Flume Any open conduit on a prepared grade, trestle, or bridge. 37. Freeboard The distance between the design flood
elevation and the top of an open channel, dam, levee, or detention basin 10 allow for wave action, floating debriS, or any Olher condition or emergencywithout overflowing the structure. 38. Functionally Dependent Use 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. 39. Harmful Quantity The amount ofany substance thaI will cause pollution ofwater in the State. 7 
40. Highest Adjacent Grade The highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure. 41. Hydraulic Gradient A line representing
the pressure head available at any given point within the drainage system. 42. Levee A man-made structure, usually an eanhen 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. 43. Levee Svs tern 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. 44. LocaiJurisdiction
The local governing body in which the construction takes place (known also as the City). 45. Lowest Floor 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 requirements ofFEMA under 44 CFR, 60.3. 46. Manning Equation The uniform
flow equation used to relate velOCity, hydraulic radius, and energy gradient slope. 47. Manufactured Home A structure transportable in one 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. For lloodplain management purposes, the term 'manufactured home' also
includes park trailers, travel trailers, and other similar vehicles placed on a site for greater than 180 consecutive days. The 'manufactured home' does not include a "recreational vehicle'.
48. Manufactured Home Park or SubdiviSion A parcel or contiguous parcels of land divided into two or more manufactured home loIS for rent or sale. 49. Maximum Extent Practicable (MEP)
The goal of pollutant reduction through the use of best managem\lnt practices. 8 
50. Mean Sea Level For purposes of the National Flood Insurance Program, the National Geode tic Vertical Datum (NGVD) of 1929 or other datum, to which base flood elevations shown on
a community's Flood Insurance Rate Map are referenced. 5 L Municipal Separate Storm Sewer System (MS4) The system of conveyances (including roads with drainage systems, municipal streets,
catch basins, curbs, gutters, ditches, man-make channels or storm drains) owned and operated by the City and designed or used for collecting or conveying storm water, and which is not
used for collecting or conveying sewage. 52. Municipal Solid Waste Solid waste resulting from or incidental to municipal, . community, commercial, institutional, or recreational activities,
and includes garbage, rubbish, ashes, street cleanings, dead animals, abandoned automObiles, and other solid waster other than industrial waste. 53. NPDES General Permit for Storm Water
Discharges Associated with IndustIial Activity (or IndustIial General Permit) The industrial industrial General Permit issued by EPA on August 27,1992 and published in Volume 57 of the
Federal Register at page 41304 on September 9, 1992, and any subsequent mOdifications or amendments thereto. 54. NPDES General Permit for Storm Water Discharge for Construction Sites
(or Constructioil General Permit) The Construction General Permit issued by EPA on August 27, 1992, and published in Volume 57 of the Federal Register at page 41217 on September 9, 1992,
and any subsequent modifications or amendments thereto. 55. NPDES Permit A National Pollutant Discharge Elimination System permit issued by EPA (or by the State under authority delegated
pursuant to 33 USC & 1342(b) that authorizes the discharge of pollutants to waters of the United States, whether the permit is applicable on an individual group, or general areawide
basis. 56. Natural 􀁄􀁲􀁡􀁩􀁮􀁡􀁾􀁥􀀠The dispersal of surface waters tllrough ground absorption and by drainage channels formed by the existing surface topography which exists at the
time of adoption of this ordinance or formed by any man-made change in the surface topography. 57. Natural Floodwav The effective area of a channel of a river or other water course and
the adjacent land areas that must be reserved in order to discharge the "design flood" without cumulatively increasing the water surface elevation. This floodway differs from the FEMA
"regulatory floodway." 9 
58. New Construction Structures for which the "start of construction" commenced on or after the effective date of Ordinance 905. 59. Non-Point Source Any source ofany discharge ofa pollutant
that is not a "point source". 60. Notice of Intent (NO!) The Notice of Intent that is required by either the Industrial General Permit or the Construction General Permit. Documentation
ofconstruction activity which is submitted to the EPA and the local jurisdiction prior to construction. It serves as notification of construction activity as well as a commitment by
the owner that he/she understands the requirements of the NPDES General Permit for Storm Water Discharges From Construction Activities and that measures will be taken to implement and
maintain a SWPPP at the site. 61. Notice ofTermination (NOD The Notice of Termination that is required by either the Industrial General Permit or the Construction General Permit. A completed
form sent to the EPA and local jurisdiction (City of Carrollton) upon stabilization of the site that serves as notice that the site is no longer subject to the requirements of the NPDES
Genera! Permit for Storm Water Discharges From Construction Activities. 62. Open Channel A channel in which water flows with a free surface. 63. OperalOr The person or persons who, either
individually or taken together, meet the follOwing two criteria: (1) they have operational control over the facility specifications (including the ability to make modifications in specifications);
and (2) they have the day-to-day operational control over those activities at the faCility necessary to ensure compliance with pollution prevention requirements and any permit conditions.
64. Other Municipal Ordinances Ordinances such as, but not limited to, zoning, subdivision, and erosion. 65. Owner The person who owns a facility or part ofa facility. 66. Person Any
individual, partnership, co-partnership, firm, company, corporation, association, jOint stock company, trust, estate, governmental entity, or any other legal entity; or their legal representatives,
agents, or assigns. This definition includes all federal, state, and local governmental entities. 10 
67. Point Source Any discernible, confmed, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, roiling
rock, concentrated animal feeding operation, landfill leachate collection system, vessel or other floating craft from which poUUlallts are or may be discharged. This term does not include
return flows from irrigated agriculture or agriCUltural storm water runoff. 68. Pollutant Dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions,
chemical waste, biological materials, radioactive materials, rocK, sand, dirt or cellar dirt generated as part of a construction project 69. Pollution The alleration. due to a construction
project, of the physical, thermal. chemical, or biological quality of, or !he contamination of, any water in the State that renders the water harmful, detrimental, or injurious to humans,
animals life, vegetation, or property, or to the public health, safety, or welfare, or impeirs the usefulness or the public enjoyment of the water for any lawful or reasonable purpose.
70. Probable Maximum Flood IPMFl The flood magnitude that may be expected from the most critical comhlnation of meteorologic and hydrologic conditions that are reasonably possible for
a given watershed. 71. Probable Maximum Precjpimtion fPMP) Theoretically the greatest depth of precipitation for a given duration that is physically possible over a given size storm
area at a particular geographical location at a certain time of the year. 72. Qualified Personnel Persons who possess the appropriate competence, s1dlls, and ability (as demonstrated
by sufficient education, training, experience, and/or, when applicable, any required certification or licensing) to perform a specific activity in a timely and complete manner consistent
with the applicable regulatory requirements and generally-accepted industry slalldards for such activity. 73. Rational Fonuula The means of relating runoff with !he area being drained
and the inlensity of the storm rainfall. 74. Recreatioool Vehicle Means a vehicle which is (l) built on a single chassis; (li) 400 square fect or less when measured at !he largest horizontal
projections; (ill) 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. 11 
75. Registered Landscape Architect (RLA) A person who has been duly licensed and registered to practice landscape architecture by the Texas Board of Architectural Examiners. 76. Registered
Professional Engineer (RPEl A person who has been duly licensed and registered by the State Board of Registration for Professional Engineers to engage in the practice ofengineering in
the State of Texas. 77. Regulatory Floodway The channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the "base flood: as calculated
by the Federal Emergency Management Agency, without cumulatively increasing the water surface elevation more than a designated height. This f100dway is used by FEMA to determine compliance
with its regulations. 78. Regulatory Zone The area within the lOO-year floodplain of the specified reach of the Trinity River as defined by the latest approved version of the digital
Trinity River Corridor Map -CDC Regulatory and Review Zones maintained by NCTCOQ, 79. Retention Basins A pond or other water body which has been designed to have both a conservation
pool for holding some water indefinitely and a flood storage pool for storing storm water runoff on a temporary basis for the purpose of reducing the peak discharge from the basin. 80.
Sanitary Sewer (or Sewer) The system of pipes, conduits, and other conveyance which carry industrial waste and domestic sewage from residential dwellings, commercial buildings, industrial
and manufacturing facilities, and institutions, whether treated or untreated, to the sewage treatment plant serving the City (and to which storm water, surface water, and groundwater
are not intentionally admitted). 81. Sediment The soil particles deposited through the process of sedimentation as a product of erosion. These soil particles settle out of runoffat variable
rates based on the size of the particle and soil type. 82. Site The land or water area where any facility or activity is physically located or conducted, including adjacent land used
in connection with the facility or activity, 83. Standard Project Flood Flood that has a magnitude of approximately one half of the probable maximum flood, as determined on a case-by-case
basis using Corps of Engineers' current criteria, 12 
84. Start of Construction For a structure, 'start of construction' includes substantial improvement and means the date the development or building permit was issued, provided the actual
start of construction, repair, reconstruction, placement, or other improvement was within 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 horne on a foundation. Permanent construction of a structure does not include land preparation, such as clearing, grading, and filling, nor does it include
the installation of streets andlor walkways; nor does it include excavation for basement, footings, piers, or foundations or the erectton of temporary forms; nor does it include 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. 85. Storm Water Storm water runoff, snow
melt runoff, and surmce runoff and drainage. 86. Storm Water POllution Prevention Plan (SWPPP) A plan required by either the Construction General Permit or the Industrial General Permit
and which describes and ensures the implementation of practices that are to be used to reduce the pollutants in storm water discharges associated with construction or other industrial
activity at the facility. 87. Structure A walled and roofed building, a manufactured horne, a gas or liquid storage tank, or a substation that is principally above ground. 88. Substantial
Improvement Any combination of repairs, reconstructions, or improvements of a structure, the cumulative cost of which equals or exceeds 50 percent of the initial market value of the
structure either: (1) before the first improvement or repair is started, or (2) ifthe structure has been damaged and is being restored, before the damage occurred. For the purpose of
this definition, definition, 'substantial improvement' is considered to occur 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. Incremental improvements over a period of time, the cumulative cost of which equals or exceeds 50 percent
of the market value at the time of the first improvement, shall be considered as a 'substantial improvement: The term does not, however, include either: (1) any project for improvement
of a structure to comply with existing State or local health, sanitary, or safety code specifications which are solely necessary to assure safe living conditions or, (2) any alteration
of a structure listed on the National Register of Historic Places or a State Inventory of Historic Places. 13 
89. Surety A corporation surety bond, cash, or certificate of deposit. 90. Time of Concentration The estimated time in minutes or hours required for a drop of water to flow from the
most remote point in the drainage area to the point at which the flow is to be determined. 91. Use Any purpose for which a building or other structure or a tract of land may be designed,
arranged, intended, maintained, or occupied; or any activity, oecupation, bUSiness, or operation carried on, or intended to be carried on, in a building or other structure or on a tract
ofland. 92. Use Permit The permit required before any use may be commenced. 93. Variance A grant of relief to a person from the requirements of this ordinance when specific enforcement
would result in unnecessary hardship. A variance, therefore, pennits construction or development in a manner otherwise prohibited by this ordinance. 94. Violation The failure of a structure
or other development to be fully compliant with this ordinance. A structure or other development without the FEMA elevation certificate prior to a certificate of occupancy, other certifications,
or other evidence as required by the City Manager, is presumed to be in viOlation until such time as that documentation is provided. 95. Watershed The area drained by a stream or drainage
system. 96. Waters of the United States All waters which are currently used, were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters
which are subject to the ebb and flow of the tide; all interstate waters, including interstate wetlands; all other waters the use, degradation, or destruction of which would affect or
could affect interstate or foreign commerce; all impoundments of waters otherwise defined as waters of the United States under this definition; all tributaries of waters identified in
this definition; all wetlands adjacent to waters identified in this definition; and any waters within the federal definition of "waters of the United States' at 40 CFR 122.2; but not
including any waste treatment systems, treatment ponds, or lagoons designed to meet the requirements of the federal Clean Water Act. 97. Water Surface Elevation The height, in relation
to the NOVD or 1929 (or other datum, where specified), of floods ofvarious magnitudes and frequencies in the floodplains of riverine areas. 14 
ARTICLE 3 GENERAL PROVISIONS SECTION A. Lands to Which This Ordinance Applies This ordinance shall apply to all areas of land within the jurisdiction of the City of Carrollton, Texas.
Certain provisions of this ordinance apply only to special flood hazard areas within the jurisdiction of the City of Carrollton, while other provisions exempt certain other tracts. These
limited areas of application are explained in the applicable provisions (See Article 8, Section A). This ordinance also extends the Scope of Authority to additional improvements on projects,
developments, subdivisions, etc. which were previously permitted and/or constructed under the authority of prior ordinances or guidelines. SECTION B. Basis for Establishing the Areas
of Special Flood Hazard The areas of special flood hazard identified by the Federal Emergency Management Agency in a scientific and engineering report entitled "The Flood Insurance Study
for the City of Carrollton: dated January 2,1991, with accompanying Flood Insurance Rate Maps and Flood Hazard Boundary·Floodway Maps and any revision thereto are hereby adopted by reference
and declared to be a part of this ordinance. The Flood Insurance Study is on file in the office of the City Engineer. SECTION C. Penalty Clause Any person, firm or corporation violating
any of the provisiOns of this ordinance shall be deemed guilty of a misdemeanor and, upon conviction, shall be punished by a penalty or fine not to exceed the sum of One Thousand Dollars
($1,000.00) for each offense, and each and every day such offense is continued shall constitute a new and separate offense. In addition, the violator shall pay all costs and expenses
involved in the case. Nothing herein contained shall prevent the City of Carrollton from taking such other lawful action as is necessary to prevent or remedy any violation. Article 4,
Section C3 states an additional penalty against persons proceeding with construction without obtaining the necessary permits from the City of Carrollton. SECTION D. Repealing Clause
The 'Storrnwater and Flood Protection Ordinance' (Ordinance No. 1375); 'Official Drainage and Storrnwater Control Ordinance' (Ordinance No. 1051); and the 'Flood Hazard Prevention Ordinance'
(Ordinance No. 905), heretofore adopted by the City Council of Carrollton, Texas, shall be and the same are hereby expressly repealed. All provisions of all ordinances conflicting with
the provisions hereof are hereby repealed. All other ordinances and provisions of such ordinances not expressly in conflict with the provisiOns hereof shall remain in full force and
effect. SECTION E. Abrogation and Greater Restrictions This ordinance is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However.
where this ordinance and other ordinance, easement, covenant, or deed restriction conflict or overlap. whichever imposes the more stringent restrictions shall prevail. 15 
SECflON F. Interpretation In the interpretation and application of this ordinance, all provisions shall be: (1) Considered as minimum requirements; (2) Liberally construed in favor of
the governing body; and, (3) Deemed neither to limit nor repeal any other powers granted under State statutes. SECflON G, Warning and Disclaimer of Uability The degree of flood protection
required by this ordinance is considered reasonable for regulatory purposes and is based on scientific and engineering considerations. Larger floods can and will occur on rare occasions.
Flood heights may be increased by man-made or natural causes. This ordinance does not imply that land outside the area of special flood hazards or uses permitted within such areas will
be free from flooding or flood damages. This ordinance shall not create liability on the part of the City of carrollton, any officer or employee thereof or the Federal Emergency Management
Agency for any flood damages that result from reliance on this ordinance or any administrative decision lawfully made thereunder. SECflON H. Severability If any section, paragraph, clause,
phrase, or provision of this ordinance shall be adjudged invalid or held unconstitutional, the same shall not affect the validity of this ordinance as a whole or any part or proviSion
thereof, other than the part so decided to be invalid or unconstitutional; nor shall such unconstitutionality or invalidity have any effect on any other ordinances or provisions of ordinances
of the City of carrollton. 16 
ARTICLE 4 ADMINISTRA TION SECTION A. Duties of City Officials I. Duties of the City Manaller The City Manager is hereby appointed to administer and implement the floodplain management
portions of this ordinance. including Articles 8 and 9 and other appropriate sections of 44 CPR (National Flood Insurance Program Regulations) pertaining to floodplain management. The
duties of the City Manager or his designee shall include but not be limited to: Review and approval of all Development Permits to determine that the permit requirements of this ordinance
have been met and that all necessary State and Federal permits have been obtained; Obtain and record the actual elevation in relation to mean sea level of the lowest habitable floor,
including basement of all new or substantially improved structures, and whether or not the structure contains a basement; Maintain for public inspection all records pertaining to the
provisions of this ordinance, including floodproofing certifications; Notify adjacent communities and and the Texas Natural Resources Conservation Commission prior to any alteration
or relocation of a watercourse, and submit evidence of such notification to the Federal Emergency Management Agency; Require that maintenance is provided within the altered or relocated
portion of said watercourse so that the flood·carrying capacity is not diminished; Make interpretations, where needed. as to the exact location of the boundaries of the areas of special
flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions); and Obtain, review, and reasonably utilize any base flood elevation
data available from a Federal, State or other source. in order to administer this ordinance when base flood elevation data has not been provided. 2. Duties of the City Engineer The City
Engineer is hereby appointed to administer and implement the storm drainage system portion of this ordinance. and to assist the Cil}' Manager with the technical aspects of the floodplain
management portions of this ordinance. SECTION B. Responsibilities ofOwners The owner or developer of property to be developed shall be responsible for all storm drainage flowing through
or abutting such property. This responsibility also includes drainage directed to that property by ultimate development as well as the drainage naturally flowing through the property
by reason of topography. It is the intent of this ordinance that provision be made for storm drainage at such time as any property affected is proposed for development, use, or modification.
17 
It is the intent of this ordinance that provision be made for storm drainage at such time as any property affected is proposed for development, use, or modification. Where the improvement
or construction of a storm drainage facility is required along a property line common to two or more owners, the owner hereafter proposing development of the property shall be responsible
for the required improvements at the time ofdevelopment, including the dedication of all necessary rights-of-way or easements, to accommodate the improvements. Where a property owner
proposes development or use of only a portion of the property, provision for storm drainage shall only be required in that portion of the property proposed for immediate development,
except as construction or improvements of a drainage facility outside that designated portion of the property is deemed essential to the development of that designated portion. Owners
shall provide for stormwater runoff and design drainage related facilities in accordance with and/or in a compatible manner with any City of Carrollton master drainage study and plan
in effect at the time when plans for drainage facilities are submitted to the City for approval. In addition, owners may be required to provide at their expense a preliminary drainage
study for the total area to be ultimately developed. This study shall be submitted to the City Engineer as a part of the submitted data for consideration of preliminary plat or site
plan approval for the portion of the property proposed for immediate development. SECTION C. Permits The City of Carrollton has several permits related to storm drainage. Some of these
permits are listed below and explained in detail in the following paragraphs. Permits required by other ordinances may also be needed. Development Permit Floodplain Alteration Permit,
formerly called the Fill Permit Corridor Development Certificate (See Article 9) 1. Develo pment Permit All developers, owners, or builders shall Obtain and submit for approval a Development
Permit application for new construction, placement of fill, new manufactured home sites, alteration of a waterway, substantial improvements to existing structures or manufactured homes,
or improvements to existing structures, or manufactured homes in the floodplain of the design flood that will result in increasing the overall outside dimensions of the structure or
manufactured home. The application form can be obtained from the City Engineer's office. The City Engineer uses this form, along with duplicate copies of the accompanying engineering
or architectural plans, to identify those construction or renovation projects that would occur in a flood hazard area. As a minimum, the engineering or architectural plans shall show,
to scale: a. The nature, location, dimensions, and elevations in relation to mean sea level of the area in question. b. The elevation in relation to mean sea level and the location of
existing or proposed structures, fill, storage of materials, and/or drainage facilities. c. The elevation in relation to mean sea level to which an existing non-residential structure
shall be f1oodproofed, the location of the foregOing. 18 
d. Any off-site facilities Or conditions that may either affect on-site conditions or be affected by on-site conditions. If an existing non-residential structure is proposed for flood
proofing, then a certificate sealed by a registered professional engineer in the State of Texas shall be submitted stating that all of the floodproofing criteria listed in Article 8,
Section B will be met. Construction or renovation projects cannot begin until the City issues the Development Permit. Floodplain Alteration Permit Developers, owners, or builders shall
Obtain a Floodplain Alteration Permit prior to filling in a floodplain; channelizing, impounding, realigning, deepening, or otherwise modifying a natural drainage way; making improvements,
substantial or otherwise, to existing structures or manufactured homes in a floodplain if the improvements result in the increase of the overall outside dimensions of the structures
or manufactured homes; or otherwise reclaiming floodplain land. A Floodplain Alteration Permit application form can be obtained from the City Engineer's office. This form along with
duplicate copies of the engineering plans, reports, etc., shall be used by the City Engineer in reviewing the permit application. Article 4, Section D.2 identifies the information that
must be submitted to the City Engineer. No floodplain alterations shall beginuntil a permit is issued by the City Engineer. 3. Corridor Development Certificate Developers, owners, or builders shall obtain a Corridor Development Certificate (CDC) prior to work
in a Regulatory Zone of the floodplain; which includes but is not limited to filling, channelizing, impounding, realigning, deepening, or otherwise modifying a natural drainageway; making
improvements, substantial or otherwise, to existing structures or manufactured homes in a floodplain if the improvements result in the increase of the overall outside dimensions of the
structures or manufactured homes; or otherwise reclaiming floodplain land. A CDC application form can be obtained from the City Engineer's office. This form along with duplicate copies
of the engineering plans, reports, etc., shall be used by the City Engineer in reviewing the CDC application. Article 9 identifies the information that must be submitted to the City
Engineer. No floodplain alternations shall begin until a CDC permit is issued by the City Engineer. 4. Elevation Certificate Developers, owners, or builders shall complete an elevation
certificate prior to issuance of a Certificate of Occupancy by the City. Elevation Certificate forms can be obtained at the City Engineer's office. 5. Proceeding Without the Applicable
Permits Any developer, owner, or builder who fails to obtain the applicable Development, Floodplain Alteration and/or CDC permit before beginning the SUbject project is in violation
of this ordinance. In addition to the penalties outlined in Article 3, Section C, no Building Permit, plat, site plan, or Certificate of Occupancy shall be issued for any construction,
reconstruction, Or development upon any land where such construction, reconstruction, or development is not in conformity with the requirements and intent of this ordinanee. Anyone who
violates any of the terms and provisions of this ordinance shall be denied a Building Permit, etc., until the violation is corrected. 19 
6. Deviations from Permit Terms Permits may be revoked by the City Engineer if. upon periodic inspection. he determines that the work is not progressing in accordance with specifications
of the approved plan and permit. Field changes to storm sewer plans can be made only upon approval by the City Engineer. Record drawings shall be submitted to the City Engineer at the
completion of the project. SECTION D. Plan Regnirements Plan requirements for stormwater drainage systems and floodplain alterations are listed below. All engineering plans shall be
sealed by a professional engineer who is registered in the State of Texas and experienced in civil engineering work. The total cost for such engineering plans and specifications shall
be borne by the owner or the developer and shall be furnished to the City Engineer for review and approval. 1. Drainage Plans As part of the platting process. drainage plans shall be
prepared. These plans shall include drainage facilities for both off-site and on-site drainage so that that the proper uansition becween the two can be maintained. Criteria for on-site
development shall also apply to off-site improvements. The construction of all improvements shall be in accordance with the current Standard Specifications for Public Works Construction
by the North Central Texas Council of Governments as amended by the City of Carrollton, and Design Standards of the City of Carrollton. The drainage plans shall include: a. Drainage
Area Map 1. Use 1'=200' scale for the development and up to 1'=2000' for creeks and off-site areas. provide that the scale is adequate for review. and show match lines between any cwo
or more maps. 2. Show existing and proposed storm sewers and inlets. 3. Indicate sub-areas for each alley. street, Off-site. etc. 4. Indicate contours on map for on-and off-site. 5.
Indicate zoning on drainage area. 6. Show points of concentration. 7. Indicate runoff at all inlets, dead-end streets and alleys, Or to adjacent additions or acreage, . 8. Provide runoff
calculations for all areas showing acreage. runoff coefficient. inlet time, and storm frequency. 9. Indicate all crests. sags, and street and alley intersections with flow arrows. 10.
Show limits ofeach plan profile sheet. 20 
b. Plan Profile Sheets 1. Show plan and profile ofall storm sewers on separate sheets from paving plans. 2. Indicate concrete cushions or embedment where applicable. 3. Specify reinforced
concrete Class 1I1 pipe unless otherwise noted. Use heavier pipe where crossing railroads, deep fill or heavy loads. 4. Indicate property lines along storm sewer and show easements with
dImensions. 5. Show all existing utilities in plan and profile of storm sewers. 6. Indicate existing and proposed ground line and improvements on all street, alley, and storm sewer profiles.
7. Show hydraulic gradient with computations. 8. Show laterals on trunk profile with stations. 9. Number inlets according to the number designation given for the area Or sub-area contributing
runoff to the inlet. 10. Indicate size and type of inlet on plan view, lateral size and flow line, paving station and top of curb elevation. 11. Indicate quantity and direction of flows
at all inlets, stubouts, pipes and intakes. 12. Show future streets and grades where applicable. 13. Show water surface at outfall of stOrm sewer, velocity, and typical section of receiving
water body. 14. Where fill is proposed or trench cut in creeks or outfall ditches, specify compacted fill and compaction criteria. 15. Show size of pipe, length of each pipe size, stationing
at one hundred foot intervals in the plan view. 16. Begin and end each sheet with even or fifty fOOl stationing. 17. Show diameter of pipes, physical grade, discharge, capacity of pipe,
slope of hydraulic gradient, and velocity in the pipe in the profile view. 18. Show elevations of flow lines at l00-foot intervals on the profile. 19. Give bench mark information. 20.
Show capacities, flows, velocities, etc., of the existing system into which the proposed system is being connected. 21. Show details of all connection boxes, headwalls on storm sewer,
flumes or any other item not a standard detail. 22. Provide lateral profiles and where utilities are crossed, show all utilities in profile. 23. Show headwalls and specify type for all
storm sewers at outfall. 24. Show if curbing in alleys is needed to add extra capacity. 25. Provide flat grade alleys and streets to discharge into streets. 26. Show curve data for all
storm sewerS. 27. Tie storm sewer stationing with paving stations. 21 
28. On all dead-end streets and alleys, show grades for drainage overflow path on the plan and profile sheets, and show erosion controls. 29. Specify concrete strength for all structures.
30. Provide sections for road, railroad and other ditches with profiles and hydraulic computations. Show design water surface on profile. c. Bridge Plans 1. Show the elevation of the
lowest member of the bridge and lOO-year water surface elevation. 2. Indicate borings on plans. 3. Provide soils report. 4. Show bridge sections upstream and downstream. S. Provide hydraulic
calculations on all sections. , 6. Provide structural details and calculations with dead load deflection diagram. 7. Provide vertical and horizontal alignment. d. Creek Alteration and
Channel Plans 1. Show stationing in plan and profile. 2 Indicate flow line, banks, design water surface, and freeboard. Show hydraulic computations. 3. Indicate nature of banks such
as rock. earth, etc. 4. Provide cross-sections with ties to property lines and easements. S. Show side slopes of creek, channels, etc. 6. Specify compacted fill where fill is proposed.
7. Indicate any adjacent alley or street elevations on creek profile. S. Show any temporary or permanent erosion controls. 9. Indicate 'existing and propnsed velocities. 10. Show access
and/or maintenance easements. 11. As necessary, show ground elevations parallel to the top of bank to show how runoff is prevented from overland flow into the creek or channel. e. Detention
and Retention Facilities 1. Show plan view of detention/retention area and outlet structure. 2 Delineate limits of conservation pool, sediment storage area, flood storage pool, andlor
freeboard. 3. Indicate size, dimension. total capacity, design discharge and velocity of the outlet structure. 4. Show any erosion control features at the discharge point of the outlet
structure. S. Specify side slopes of basin and outlet structure. 22 
6. Show existing or proposed structures or other facilities down stream of the outlet structure and emergency spillway, and provide information sufficient to show that the downstream
facilities will not be inundated or otherwise affected by the discharge from the basin. 7. Indicate locations and quantities of all inflows to the basin. 8-State the design time to empty
the basin. f. Levees l. Show location, extent, nature, dimensions, etc., of levee embankments and associated interior and exterior drainage facilities. 2. Provide engineering analysis
addressing potential erosion of the levee embankments during flood events. 3. Provide engineering analysis of levee embankment stability and seepage through the levee during flood events.
4. Demonstrate that future settlement of the levee embankments will not result in freeboard dropping below the minimum requirements. Provide geotechnical reports showing anticipated
levee consolidation. S. Analyze interior drainage concerns. Identify sources of interior flOOding, flOOding, and extent and depth of such flooding, assuming a jOint probability of interior
and exterior flooding. Consider capacity of pumps and other drainage devices for evacuating interior waters. 6. Write an operations manual which discusses the flood warning system to
trigger closures; closure operations, procedures, and personnel; operation plans for interior drainage facilities; at least an annual inspection program; and maintenance plans, procedures,
and frequency. 7. Provide aU other information required in Article 7, Section C, and any other information requested or required by the City Engineer and/or the Federal Emergency Management
Agency. 2. Floodplain Alteration Plans The materials listed below shall be submitted as par! of the application for a Floodplain Alteration Permit. It is recommended that applicants
coordinate the application materials listed below with those needed for other City of Carrollton permits and with the data requirements of the Federal Emergency Management Agency. Such
coordination will faciIttate staff review and drawings could be combined so as to save the applicant from multiple drawings. a. An engineering report consisting of at least: L Project
description. 2. Description of the hydrologic and/or hydraulic analyses used, including method used to determine historic rainfall and stream data, soils reports used to determine erosive
velocity values, and diScharges and water surface elevations for both the design and base floods. 3. Vicinity map. 
4. Evaluati?n of the "natural floodway" and floodplain limits for the design flood. The "natural' f1oodway' differs from the FEMA 'regulatory f1oodway." The "natural f1oodway' is established
to allow the City of Carrollton to effectively manage flood plain areas. FEMA requirements for the 'regulatory f1oodway" must also be met by applicants. 5. If hydraulic analyses are
being submitted, then a table of values for existing and proposed water surface elevations and velocities must be included. 6. Documentation that the principle ofequal conveyance has
been achieved. 7. Copies of computer input and output data for existing and proposed conditions for both the base flood and design flood discharges. b, Engineering drawings consisting
of at least: 1. Water surface profile, including channel flow line, existing and proposed water surface elevations, recorded high water marks, and location and number designation of
cross-sections. 2. Plan view on 24' x 36' paper, including a. Scale and north arrow. b. Title block. block. c. Boundary lines and nearest street intersections. d. Existing and proposed
contours. e. Existing and proposed floodplain limits, and limits of the 'natural f1oodway" and the 'regulatory f1oodway.' f. Area to be removed from the floodplain or area to be altered.
g. Top and toe of fill and/or side slopes and the numerical slope of the fill and/or side slopes labeled. h. Location of all other associated improvements or alterations to the creek
and/or floodplain, such as check dams, swales, channel modifications, etc. i. Location of cross-sections. j. Location of all existing and proposed easements and dedications. k. Site
vicinity map. 3. Plots of cross-sections, including: a. Scale. b. Title block. c. Existing and proposed ground elevations. d. Cut and/or fill areas labeled. e. Limits of and numerical
values for existing and proposed 'n'values. f. Equal conveyance removed from both sides. SECTION E. Maintenance Bonds The Contractor shall guarantee the work which he does against defective
workmanship and materials for a period of two (2) calendar years from the date offinal acceptance by the City. Where defective workmanship and/or materials are discovered requiring repairs
to be made under this guarantee, all such repair work shall be done by the Contractor at his own expense within ten (10) calendar days after written notice of such defect has been given
to him by the City. Should the Contractor fail to make 24 
repair or correct such defective workmanship and/or materials within ten (10) calendar days after being notified, the City may make the necessaTY repairs and charge the Contractor with
the actual cost of all labor and materials required. The Contractor shall provide a maintenance bond in the amount of 100% of the contract price, for a period of two (2) years after
the date ofacceptance of the work to cover his guarantee as set forth above. SECTION F. Appeals and Variance Procedure 1. Appeal Any person aggrieved by a decision of the City Engineer
or City Manager may appeal from any order, requirement, decision or determination of the City Engineer 10 the Planning and Zoning Commission. An appeal from a determination of the Planning
and Zoning Commission may be made directly to the Court of Appeal. 2. Variances The Planning and Zoning Commission as established by the City of Carrollton shall hear and decide requests
for variances from the requirements of this ordinance. Variances concerning Development Permits may be issued for the reconstruction, rehabilitation or restoration of structures listed
on the National Register of Historic Places or the State InventoTY of Historic Places, without regard to the proeedures set forth in the remainder of this section. Variances shall not
be issued within any designated natural or regulatoTY floodway if any increase in flood elevations during the design flood discharge would result unless the increase will result in no
negative impacts on adjacent properties and written approval is obtained from impacted property owners. Variances shall be issued only upon a determination that the variance is the minimum
necessaTY to afford relief conSidering the flood hazard, drainage problems, and soil loss. Variance shall be issued only upon meeting all three of the following criteria: 1. A showing
of good and sufficient cause. 2. A determination that failure to grant the variance would result in exceptional hardship to the applicant; and, 3. A determination that the granting of
a variance will not result in increased flood heights, additional threats to public safety, extra ordinaTY publiC expense, create nuisances, cause fraud on or victimization of the public,
or conflict with existing local laws or ordinances. Any applicant to whom a variance for building or renovating in a floodplain is granted shall be given written notice that the structure
will be permitted to be built with a lOwest floor elevation below the design flood elevation and that the cost of flood insurance will be commensurate with the increased risk resulting
from the reduced lowest floor elevation, 25 
In considering variance requests, the Planning and Zoning Commission shall consider aU technical evaluations, all relevant factors, standards specified in other sections of this ordinance.
and the: Danger that materials may be swept onto other lands to the injury of others; Danger to life and property due to drainage, flooding, or erosion damage; Susceptibility of the
proposed facility and its contents to flood damage and the effect ofsuch damage on the individual owner; Importance of the services provided by the proposed facility to the community;
Necessity to the facility ofa waterfront location. where applicable; Availability of alternative locations for the proposed use which are not subject to flooding damage. Compatibility
of the proposed use with existing and anticipated development. Relationship of the proposed use to the comprehensive plan and flood plain management program of that area. Safety of access
to the property in times offlood for ordinary and emergency vehicles; Expected heights, velocity, duration, rate of rise, and the effects of wave action, if applicable, expected at the
site; and, Costs of proViding governmental services during and after storm events, including maintenance and repair of public utilities and facilities such as sewer, gas, electrical,
and water systems, and streets and bridges. Upon consideration of the factors listed above and the purposes of this ordinance, the Planning and Zoning Commission may attach such conditions
to the granting of variances as it deems necessary to further the purposes of this ordinance. The City Manager shall maintain the records of all appeal actions, including technical information,
and report any variances of the floodplain management portions of this ordinance to the Federal Emergency Management Agency upon request. 26 
ARTICLES RUNOFF CALCUIA nONS The selection of which method to use for calculating runoff depends upon the size of drainage area contributing runoff at a most downstream point of a project.
The "Rational Method' is acceptable for situations in which the drainage area is less than 160 acres. A unit hydrograph method is required for situations with larger drainage areas.
No matter which method is used to calculate runoff, a developer or builder of property greater than one acre in size, or any property that was platted as a part of an overall tract which
was greater than one acre in size (includes churches and schoolS). shall develop the property so that the rate of runoff created by the development as it leaves the property does not
exceed the rate of runoff that would have been created if the property had developed as single·family residential property. Article 7. Section D discusses design criteria for detention
facilities. Runoff computations shall be based upon fully developed watershed conditions in accordance with the land use projections in the latest comprehensive land use plan for the
City of Carrollton. The design engineer shall size drainage facilities by disregarding the detention effects of upstream property and calculating the runoff as if the off·site property
was developed without any detention. If an approved regional detentiOn/retention facility is in operation. the design engineer may size downstream drainage facilities based on consideration
of the detention effects of the regional facility. SECTION A. Procedure for Drainage Areas Less Than 160 Acres 1. Rational Method Computation of Stormwater Runoff for drainage areas
less than 160 acres shall be by the 'Rational Method," which is based on the prinCiple that the maximum rate of runoff from a given drainage area for an assumed rainfall intensity occurs
when all parts of the area are contributing to the flow at the point of discharge. The formula for calculation of runoff by the "Rational Method" is: (Equation 1) Q = C(CIA Where: Q
= the maximum rate of discharge, expressed in cubic feet per second. Cf = frequency factor coefficient for adjustment of the rational method C value. This factor varies from 1.00 to
1.2.5 for the 10-year and l00-year storms respectively. C = a runoff coefficient which varies with the topography, soil. land use and moisture content of the soil at the time the runoff
producing rainfall occurs. This runoff coefficient shall be based on the ultimate use of the land as recommended by the Master Plan for the City of Carrollton and shall be selected from
Table 1 herein on the basis of the use shown on land use and zoning map of the Comprehensive Zoning Ordinance for the City of Carrollton. If an area has had a change of Zoning to give
the area land use for which the "C" in Table 1 is higher than use shown on land use and wning maps, the higher "C' factor shall be used. 27 
A = The drainage area, expressed in acres, contributing to the runoff at the point in question. Calculation of the drainage area shall be made from an accurate topographic map, a copy
of which shall be submitted with the engineering plans for approval. I = Rainfall intensity in inches per hour for the time period that it takes for flow from the farthest point of the
drainage area to reach the point ofdesign. The rainfall intensity is found by referring to the applicable curves of Figure 1. Time of Concentration or Duration of Rainfall for use in
Figure 1 shall be calculated by velocity data shown in Table 2. Time of concentration is the longest time, without interruption of flow by detention devices, that a drop of water takes
to flow from the farthest point of the drainage area to the point of concentration (i.e., the point of design). The lime of concentration is composed of the 'inlet time' and the flow
time in a conduit or channel to the point ofdesign. Equation 2 shows how to calculate the time of concentration. (Equation 2) L Tc = Inlet Time + =-.:c;::--;--;-V x60 sec/min Where:
Tc = Time of concentration in minutes. Inlet time =10 minutes for property zoned multiple family, Churches, schools, local business, central business, commercial, or industrial or 15
minutes for property zoned for parks, cemeteries, agricultural, and single family residential. or L V x 60 sec/min L =Length of conduit or channel, in feet. V = Velocity of flow in conduit
or channel, in feet per second. When designing inlets and laterals, the time of concentration is simply equal to the inlet time. The design engineer will compare the above specified
inlet times to the actual calculated inlet lime by computing the flow time overland and along the gutter to the first inlet. The Manning equation. along with the velocity information
in Table 2 (or other acceptable procedures such as the SCS method), shall be used to determine flow time to the inlet. The design engineer may use the actual calculated or specified
inlet time. In no case shall a longer inlet time be used than 10 minutes for multiple family, commercial, churches, schools, industrial and business areas and 15 minutes for parks, cemeteries,
agricultural, and single-family areas. 28 
When sizing storm sewers and channels, the time of concentration shall be calculated by adding the actual calculated inlet time (but not greater than the specified inlet times) to the
flow time in the conduit and/or channel. The design engineer may use the combined times, as described, or the specified inlet times for storm sewer sizing. SECTION B. Procedure for Drainage
Areas Greater than 160 Acres. For drainage areas in excess of 160 acres where the use of the 'Rational Method' does not provide reliable results, the use of a unit hydrograph method
shall be made. The use of a unit hydrograph calculation will be based upon standard and accepted Engineering Principles normally used in the Profession subject to the approval of the
City Engineer. Acceptable methods include the Soil Conservation Service (SCS) Technical Release Number 55 for drainage areas from 160 acres to 2,000 acres, and SCS's TR20 or the Corps
of Engineers HEC-l models for drainage areas 160 acres or more. The unit hydrograph method shall be be based upon fully developed watershed conditions assuming no effects from the small
on-site detention facilities for maintaining the rate of runoff as if the property was developed as single family residential uses. The detention effects of large regional detention
facilities can be taken into account in unit hydrograph methods. Circumstances that may require the use of a unit hydrograph method include sizing open channels, reclaiming floodplains,
creating lakes, or building other types of drainage-related facilities on major drainage courses. Design engineers of these types of facilities should be aware that the requirement of
designing for fully developed watershed conditions will mean that they will have to calculate these fully developed flows instead of using the flows calculated in the Federal Emergency
Management Agency's (FEMA) flood insurance studies for Carrollton. FEMA's flows cannot be used because the flows are based upon existing watershed conditions (For more information, see
Article 7 on the sizing of channels and other major drainage facilities and Article 8 for floodplain alteration procedures). Use of the rational method is allowed for design of storm
sewers within the project area. 29 
ARTICLE 6 DESIGN OF LOCAL DRAINAGE SYSTEMS SECTION A. Desilln SOOrm Frequencies The calculations of runoff quantities that must be accommodated in drainage facilities require the selection
of the design storm frequency. The design storm frequencies for various drainage structures are given below. DRAINAGE FACILITY DESIGN RECURRENCE INTERVAL Closed Storm Sewer Systems IO-year
with lOO-year positive overflow for Inlets on Grade in streets such that the depth of flow in the street does not exceed the top ofcurb. Closed Storm Sewer Systems and Inlets lOO-year
at Street Low Point or Sag Culverts and Bridges Concrete-lined Channels 1()O..year Earthen Channels lOO-year Levees Standard Project Flood Dams Above Natural Ground/Spillways Spillway
design flood varies with the class of structure (see Article 7, Section B). The approved drainage system shall provide for positive overflow at all low points. The term "positive overflow"
means that when the inlets do not function properly or when the design capacity of the conduit is exceeded, the excess flow can be conveyed overland along a grassed or paved course.
Normally, this would mean along a street or alley, or shall require the dedications of special drainage easements on private property. SECTION B. Street and Alley Capacities Assuming
parkway slopes to be 114 inch per foot behind the curbs, the depth of flow in the streets shall not exceed the top of curb. Figure 2 shows the capacity of streets with a straight cross
slope that varies from 118 inch per foot to 112 inch per foot, which are the minimum and maximum allowable street cross slopes. Figures 3 and 4 show the capacity of streets with parabolic
croWnS. 2. 􀁾􀀠The flows created by the lOO-year storm shall be contained within the capacity of all paved alleys. Figure 5 shows the capacity of various alley sections. 30 
Alley capacities shall be checked at all alley turns and "r intersections to determine if curbing is needed or grades should be fiattened. Alley sections shall be super-elevated as required
at corners and curves to insure that flow remains in the alley through these changes in alignment Curbing shall be required for at least 10 feet on either side of an inlet in an alley
and on the other side of the alley so that the top of the inlet is even with the high edge of the alley pavement. 3. Finished F100r Elevations in Relation to Alleys, Streets, and Positive
Overflows The first floor elevations of all residential and other structures shall be set at a minimum elevation of the lower of either 1.5 feet above the alley invert or one foot above
the top of the street curb elevation, and with positive drainage provided away from the structure. Positive overflow sections shall provide a minimum of 2 feet of freeboard from the
overflow invert adjacent to structures and the corresponding first floor elevation of all residential and other structures. SECfION C, Placement orInlets Storm sewer inlets shall be
built along paved streets at such intervals that the depth of flow, based upon the l00-year storm, does not exceed the top of curb. Inlets shall be located as necessary to remove the
flow based on a lO-year storm. If in the opinion of the City Engineer the flow in the gutters would be excessive using the a hove design criteria, the storm sewers or inlet locations
could be altered to relieve adverse conditions. Inletsshall be placed upstream from an intersection whenever possible. At any intersection, only one street shall be crossed with surface drainage and this street shall be the lower classified
street. When an alley intersects a street, inlets shall be placed in the alley whenever flow down that alley would cause the capacity of the intersecting street to be exceeded. SECfION
D. Inlet Capacities and Sizes Fignre 6 shows the various types of inlets allowed for use along various kinds of streets. Other types of inlets may be used upon the approval of those
inlets by the City Engineer. The minimum inlet size shall be eight feet. Figures 7 through 21 show how to determine the capacity of inlets. No more than 20 feet of inlets shall be placed
along one gutter at any given location. Minimum sizes oflaterals shall be 18-inches for use with 8-foot inlets, and 21-inch laterals with 10-foot. 14foot, and drop inlets, and 24-inch
laterals for 2O-foot inlets. Where laterals tie into trunk lines, place the laterals on a 60 angle with the trunk line and connect them so that the longitudinal centers intersect. SECfION
E. Pipe Design StandardS 1. The Manning Equation Storm sewer conduit shall be sized to flow full. Manning's Equation shall be used to determine the conduit size. Manning's equation is
expressed as: 31 
(Equation 3) 1.486 '>" 1f2 1.486 '>n 1/2Q '" _ (A) (R),,",J (S) or V = (R)""IJ (S) n n Where: Q '" Row in cubic feet per second. V = Velocity of flow in conduit in feet per second. A
= Cross-sectional area of the conduit in square teel. R '" Hydraulic radius of tile conduit, which is the area of flow divided by the wetted perimeter (R =AlP). S = Slope of the hydraulic
gradient. n '" Roughness coefficient of the conduit. P = Wetted perimeter. Figure 22 is a graphical solution of Manning's Equation, which allows sizing of concrete pipe, assuming an
"n° value of 0.013. 2. Minimum and Maximum Velocities in Pipes The minimum velocities in conduit shall be 2 . .5 feet per second. The minimum slopes for various pipe sizes that will
maintain this minimum velocity are given in Table 3. The recommended maximum velocities offlow in the conduit and channels are given in Table 4. The maximum discharge velocities in the
pipe shall also not exceed the permitted velocity of the receiving channel or conduit at the outfall to prevent erosive conditions, as shown in Table 4. The maximum outfall velocity
of a conduit in partial flow shall be computed for partial deptb and shall not exceed the maximum permissible velocity of the receiving channel unless controlled by an appropriate energy
diSSipater (e.g. stilling basins, impact basins, riprap protection). 3. Roughness Coefficients for Conduits In general, stormwater shall be carried in concrete pipe conduit, but other
types of conduit can be used to carry stormwater. However, prior permission to use metal conduit must be obtained from the City Engineer. Table.5 shows recommended roughness coefficients
for various types of conduits. If, in the opinion of tbe design engineer, other values for the roughness coefficient should be used, the different value can be used with the permission
of tbe City Engineer. Appropriate notes of the approved roughness coefficient shall then be shown on the engineering plans. 32 
4. Hydraulic Gradient of Conduits Conduits must be sized and slopes must be set such that runoff flows smoothly down the drainage system. To insure this smooth passage, the hydraulic
gradient must be at the proper elevations. The proper starting elevation of the hydraulic gradient shall be set according to the applicable criteria listed below: 1. When a proposed
conduit is to connect to an existing storm sewer, the hydraulic gradient of the proposed storm sewer should start at the elevation of the hydraulic gradient of the existing storm sewer
based on an evaluation of the existing storm sewer with respect to the requirements found in this ordinance. This criterion will be used for existing systems whether or not they are
designed in accordance with this ordinance. 2. When a proposed conduit enters an open channel, creek, or flood control sumps, the hydraulic gradient of the proposed conduit should start
at the 10-year water surface elevation of the channel or creek when the ratio of the drainage area of the receiving creek (at the development) to the development area is 15 or greater.
For ratios of less than 15, the l00-year water surface will be used on the receiving creek. Not only is it important to use the proper starting elevation for the hydraulic gradient,
but proper hydraulic gradient elevations must be maintained for the length of the conduit. The inside top of the conduit should be at or below the hydraulic gradient. However, effort
should be made to keep the top of the pipe as close to the hydraulic gradient as possible so that deep excavations to lay pipe are not required. When the conduit is flowing partially
full, the hydraulic gradient shall be shown at the inside crown of the conduit. The hydraulic gradient shall be kept two feet below the top of curb. If this cannot be obtained, the hydraulic
gradient shall be at least 1.5 V12f2g feet below the gutter line, where V 1 is the velocity in the lateral. 5. Minor Head Losses When establishing the hydraulic gradient of a storm sewer,
minor head losses at points of turbulence shall be calculated and included in the computation of the hydraulic gradient. Entrance Losses Entrance losses to a closed storm sewer system
from an open channel or lake shall be calculated using Equation 4. 33 
I (Equation 4) Where: HL = Head loss in feet. VI = Velocity in the downstream pipe in feet per second. Ke = Head loss coefficient (see Table 6). The resulting hydraulic gradeline shall
be compared to inlet control conditiOns for the storm sewer as described in Section F. The higher of the two values will be used as the controlling upstream hydraulic grade line. Expansion
Losses For pipe size expanSions, head loss shall be calculated using the following equations: (Equation 5) Where: HL = Head loss in feet. VI = Upstream velocity in feet per second. 01
= Upstream pipe diameter. 02 = Downstream pipe diameter. Manhole and Bend Losses Head losses associated with manholes for pipe direction changes and bends in pipes of equal diameter
shall be calcula ted using: (Equation 6) Where: H L = Head loss in feet. V2 = Velocity in the downstream pipe in feet per second. Kb = Head loss coefficient from Table 7. 34 
Junction Losses Head losses associated with wye connections or manholes with branch laterals entering the main line can be calculated by using Equation 7. (Equation 7) Where: HL = Head
loss in feet. VI = Velocity in the upstream pipe in feet per second. V2 = Velocity in the downstream pipe in feet per second. Kj = Head loss coefficient from Table 7. 6. Storm Sewer
Laterals Laterals for storm sewer systems shall be sized to control the flooding depth at the inlets. The depth shall not exceed the limits previously established for storm sewer systems.
Calculation of the flooding depth shall be determined based on the addition of the velocity head of the lateral to the computed HGL: ELEV =HGL + VL2 2g This calculated elevation shall
be compared to the elevation determined based on inlet control nomographs as developed by the Department of Transportation. The highest of the twO elevations shall be used to establish
the capacity of laterals and the corresponding depth offlooding. 7. Outfalls to Open Channels and Lakes The flow lines ofstorm sewer conduits that discharge into open channels shall
match the flow line of the channel. One exception to this requirement of matching the flow line is when a storm sewer discharges into a concrete-lined channel. or when the outfall is
submerged below the normal water surface of a lake. In the case of a pipe discharging to a lined channel, the outlet must be below the top of the channel lining. The second exception
pertains to storm sewer discharge that must cross wide floodplain areas. Under this condition, the storm sewer could discharge into a lined ditch which would convey runoff to the flow
line of the channel without creating an erosive condition. Permissible velocities within the ditch will be based on the type of lining used and the velocities provided in Table 4. Flumes
to bring the disCharge down to the flow line of earthen creeks shall not be permitted. Drop structures shall be allowed upon written approval of the City Engineer. The velocity at the
discharge end of the conduit shall be computed based on partial flow depth and shall be sufficiently low so as to not cause downstream erosion problems. Table 4 shows the maximum velocities
allowed in various types of channels. which are then the maximum discharge velocities at storm sewer outfalls. 35 
In some circumstances. the configuration of the storm sewer in relation to the flow line of the creek may cause excessive velocities to be reached unless provisions are made to slow
tbe velocity. One recommended metbod of slowing the velocity is to have the last length of pipe (a length of at least ten times the diameter) be on a slope that will reduce the partial
flow outlet velocity to the values shown in Table 4 for the receiving stream. Stilling basins shall also be allOWed to reduce discharge velocities. The discbarge pipe shall also intersect
minor creeks at an angle not to exceed 60 degrees. Minor creeks are defined as those creeks. cbannels. or drainageways where the distance from the pipe outlet to the opposite creek bank
at the bottom of the channel is twenty (20) feet or less. Pipes may intersect major creeks (greater than 20 feet to opposite bank) at a9Q.degree angle. The City Engineer may require
that pipes intersect major creeks at an angle not to exceed 60 degrees, when a 9Q.degree angle would result in an erosive condition. Figure 23 shows how a storm sewer sbould be configured
to discharge into a creek. 7. Easements for Enclosed Storm Sewers and Positive OverQow Areas All storm sewer conduits to be dedicated to the City of Carrollton shall be located in an
easement dedicated to the City of Carrollton at the time of final platting of the property. The easement shall be at least 15 feet wide for storm sewers or wider if the City Engineer
reqUires it for maintenance or Other purposes. Special drainage easements on private property sball be a minimum of 10 feet wide or wider if the City Engineer reqUires it for maintenance
or other purposes. No fences, buildings or other structures and improvements shaH be placed within these dedicated easements. SECTION F. Culvert Design Standards Culverts shall be designed
in accordance with the Texas Highway Department Hydraulic Manual. Cbapter 4· Culverts. The calculation of hydraulic grade lines will consider botb inlet and outlet control for the culvert.
Starting water surface elevations for gradeline calculation will be the same as required for storm sewers; see Section E. 36 
ARTICLE 7 Sl'E.CIAL DRAINAGE FACILITIES SECTION A. Channels L Channel Design Open channels may be used instead of enclosed systems when the drainage area of contributing flow to the
channel is greater than 160 acres. Open channels shall not be permitted when the drainage area is less than 160 acres. Table 4 shows the maximum velocities allowed for certain types
of channels. Roughness coefficients for the design of open channels are provided in Table 8. The following criteria shall be used in determining the nature of the open channel. 􀀮􀁆􀁑􀁌􀁾with
a contributing drainae-e area QJ 160 acres Of greater: a. Channels may be left in their natural state provided that the channel velocities are 6.0 feet per second or less. b. If the
natural channel is to be replaced by an improved channel, the flow from the IOD·year design flood must be contained within the improved channel while allowing for one foot of freeboard.
An improved channel shall meet the floodplain alteration regulations presented in Article 8. c. Improved channels shall include a lined section if the design velocity is greater than
six feet per second. Lining types such as concrete, rock walls and gabions, may be used upon approval of the City Engineer. Improved channels with design velocities of less than the
permissible velocities shown in Table I I may be earthen if the channels are revegetated properly. d. For lined channels, all of the channel bottom and at least the first three feet
(vertical height) of the side slopes up from the channel bonom shall be lined, unless approved by the City Engineer. e. Earthen sides above the lined section or totally earthen channels
shall be on at least a four horizontal to one vertical slopes and shall have approved ground cover to prevent erosion. f. Unless shown to be feasible in a soils report sealed by a registered
professional engineer in the State of Texas, and approved by the City Engineer. improved channels shall have minimum side slopes of: 4 feet horizontal to I foot vertical for earthen
grassed side slopes. 1.5 feet horizontal to I foot vertical for side slopes in rock. g. The developer or owner shan use low maintenance vegetation for vegetative cover, as approved by
the City Engineer prior to planting. The selection of materials shall comply with either the current ground cover listing for North Central Texas furnished through the Texas Agricultural
Extension Service or Table 9 in this ordinance. 37 
h, The developerlowner shall provide a drainage easement and a required maintenance easement (see paragraph 4 below) which shall be dedicated to the City of Carrollton as a penn anent
drainage right-of-way and open space corridor. i. Channel improvement shall not include concrete pilot channels which do nOI meet the requirements of item A, I,d" unless approved by
the City Engineer. 2. Erosion Prevention All channel sections must consider and account for channel stabilization in their design, This requirement pertains to all sections whether they
are left in their natural condition or are modified in any manner. Three sets of requirements are provided depending upon the relationship of the existing channel to the limits of the
developerlowner's property boundaries. The City Engineer shall have the discretion to require the implementation of the portion of these requirements as deemed necessary, depending on
the specifics of the property being developed or improved, a, In cases where the entire channel section is contained within the limits of the developer/owner property boundaries, The
developerlowner shall: I. Provide for an improved stabilized channel cross-section which reduces all velocities to 6,0 fps or below for vegetated channels. The channel improvements must
meet all requirements of this oroinance, 2. For vegetated channel sections with channel velocities ranging from 6 to 8 fps, construct grade control structures within the channel and
overbank areas to prevent erosion, Grade control structures shall have a minimum effective depth of 3,0 feet below existing or proposed grades with an adequate number of structures to
prevent less than I foot of degradation. b, In cases where the property boundary follows the centerline of the channel or incorporales only a portion of the channel cross-section, the
developer/owner shall: 1, Detennine the design section required to provide for an improved stabilized channel cross-section which reduces all velocities to 6.0 fps or below for vegetated
channels, The design channel section must meet all requirements of this oroinance, 2, The design section may include vegetated channel sections with channel velocities ranging from 6
to 8 fps, provided that grade control structures are included within the channel and overbank areas to prevent erosion, Grade control structures shall have a minimum effective depth
of 3.0 feet below existing or proposed grades with .n adequate number of structures to prevent less than I foot of degradation, 3, The developer/owner shall construct the portion of
lhe design improvements required on their property for the ultimate channel design. The City Engineer shall have the discretion to detennine the portion of the design improvements to
be constructed by the developerlowner, In most instances, the developerlowner shall construct one-half of the improvements on their property, 4, If grade control structures are incorporated
into the design, the developerlowner shall coordinate with adjacent owners in order to construct 38 
these features in their entirety at the time of the initial portion of the channel improvements. 5. The developer/owner shall provide for a drainage easement and accesslmaintenance easement
consistent with the portion of the improvements provided. c. In cases where the developer/owner owns property adjacent to channel or floodplain areas but does not Own a portion of the
channel or floodplain area, the developer/owner shall (at the discretion of the City Engineer): I. Determine the channel improvement configuration necessary to meet the requirements
of item (2a) above and 2. ShaH provide a dedicated easement to the city for the portion of this future improvement configuration, including necessary maintenance and access easement,
which will include the developer/owner property. 3. 􀁓􀁴􀁡􀁲􀁴􀁩􀁮􀁾􀀠Water Surface Condition When performing hydraulic analyses for channel or drainage way design, the starting water
surface shall be based on the following criteria. a. When the ratio of the drainage area of the receiving creek (at the confluence location) to the drainage area of the channel or drainageway
being designed is 15 or greater, the lO-year water surface of the receiving creek shall be used as the starting water surface for hydraulic design calculations. For creeks where the
lO-year water surface is not available, the slope-area method will be used for starting design calculations. b. When the ratio of the drainage area is less than 15, the I()()..year elevation
On the receiving creek shall be used as the starting water surface for design calculations. 4. Easements Required for Open Channels Drainage andlor flood way easements for all open channels,
creeks and flumes shall be dedicated to the City of Carrollton. Easements shall encompass all areas having a ground elevation below the higher of One foot above the water surface elevation
associated with the design flood or the top of the high bank or channel edge. No fences, buildings, or other structures which could impede flow shall be placed within this dedicated
drainage easement. In all cases, the easement shall also include at least a 15-foot wide maintenance strip along bOlh sides of the channel or, if the City Engineer so a!lows, at least
a 20-foot wide maintenance strip along one side of the channel. Streets, alleys, bike paths, etc., alongside the channel can serve as all or part of the maintenance easement. Drainage
easements for flumes shall be located with sufficient width to permit future maintenance accessibility, and in no case shall be less than 15 reet wide. SECTION B. Lakes and Dams In the
event that a property Owner or developer desires to modify an existing pond or lake or desires to impound slorrowater by filling or constructing an above-ground dam, thereby creating
a lake, pond, lagoon or basin as part of the planned development of that property, the criteria listed below shall be met before City 39 
approval of the impoundment can be given. Ponds or lakes. created by excavation of a channel area without erecting a dam above natural ground elevation or instream, low water checkdams
are also subject to the criteria listed below, with the exception of spillway capacity requirements. The City Engineer has the final authority to detennine the design criteria for a
proposed dam, checkdam or excavated lake. The requirements of the State of Texas must also be met for the construction of dams, lakes, and other impoundments. The design criteria for
a dam is dependent on the size and hazard classification of the dam. The size and hazard classification will be based on Chapter 12 of the Texas Water Code and will be detellIlined by
the City Engineer based on infollIlation furnished by the owner. The following criteria will be used to classify a dam: L 􀁾􀀠The classification for size is based on the height of the
dam and storage capacity. whichever gives the larger size category. Height is defined as the distance between the top of the dam (minus the freeboard) and the existing streambed at the
downstream toe. Storage is defined as the maximum water volume impounded at the top of the dam (minus the freeboard). Size Classification Impoundment Category Storage (acre-feet) Height
(feet) Minor <100 <10 Small 􀁾􀁬00 and < 1,000 ;,,10 and < 40 IntellIlediate 􀁾􀁉􀀮􀁏􀁏􀁏􀀠and < 50,000 ;;,40 and < 100 Large <!SO,OOO ;,,100 2. HaM Potential The hazard potential for
a darn is based on the potential for loss of human life and property damage downstream from a darn in the event of failure. The following categories will be used: 􀁾􀁊􀀧􀁑􀁴􀁥􀁮􀁴􀁩􀁡􀁬􀀠Classificati
on Loss afLife Economic Loss Category (Extent of Development) (Extent of DeveJonrnenO Low None expected (No pennanent Minimal structures for human habitation) (Undeveloped to occasional
structures or agriculture) 40 
Hazard Potential Classification Loss ofUfe Economic Loss Category (Extent of DevelOlJment) (Extent of Deve!Qprnen t) Significant Possible. but not expected (No urban Appreciable developments
and no more than a (notable small number of inhabitable structure agricultural. industry. or commercial development) High Expected (Urban development or large Excessive number of inhabitable
structures) (Extensive public. industrial. or agricultural development) 3. SpillwilY Design Flood The classification of a dam based on the above criteria will be used to determine the
Spillway Design Flood (SDP). The total capacity of a dam structure. including principal and emergency spillways, shall be adequate to pass the SDF without exceeding the top dam elevation
at a minimum. The SDFs for various dam classifications are as follows: Spillway Design Flood Low Minor lOO-year Small 1I4PMF Intermediate 114 PMF to 112 PMF Large PMF Significant Small
1/4 PMF to 112 PMF Intermediate 112 PMF to PMF Large PMF High Small PMF Intermediate Intermediate PMF Large PMF In all cases. the minimum principal spillway design capacity is the IOO-year
design flood. In certain cases, a dam breach analysis may be required to determine the proper classification of the structure. For all structures requiring a spillway design flood equal
to the PMF, a dam breach analysis is required to determine the downstream consequences of a failure. All dams designed for a SDF of 112 PMF or less shall be constructed with a minimum
freeboard of two feet above the SDF elevation. 41 
4. Additional Design Requirements a. An engineering plan for such construction, accompanied by complete drainage design information and sealed by a registered professional engineer,
shall have been approved by the City of Carrollton; b. The spillway and any emergency overflow areas shall be located so that flood waters will not inundate any buildings. roadways,
or other structures. c. All Federal, State and County laws pertaining to impoundment of surface water shall have been complied with, including the design construction and safety of the
impounding structure. Copies of any Federal. State, and County permits issued for the proposed impoundments shall be submitted to the City Engineer. d. Any existing structure, which
is included in the project area shall be improved to comply with the applicable Federal, State, County and City safety requirements for structures. e. Before removing. enlarging, or
altering any existing lake. the Owner will furnish a study of the effects of the alteration upon flooding conditions both upstream and downstream. The study shall be prepared by a professional
Engineer and submitted to the City for approval prior to making the proposed alteration. Compensatory storage shall be provided in some manner such that equal or comparable flood retention
capacity is maintained. f. Any improvements to existing dams or lakes or construction of new impoundments shall be made at the expense of the developer, prior to acceptance of the adjacent
street, utilities and drainage improvements as provided for under the Subdivision Ordinance. 5. Maintenance and Liability Criteria a. The owner or developer shall have agreed to retain
private ownership of the lake, pond, or lagoon or basin constructed and to assume full responsibility for the protection of the general public from any health or safety hazards related
to the lake, pond, or lagoon constructed. b. The owner or developer shall have agreed to assume full responsibility for the maintenance of the lake, pond, or lagoon or basin constructed.
The owner or developer shall keep the Director of Public Works advised of the current responsible agent for this maintenance. SECTIONC. 􀁾􀀠In the event that developers or owners wish
to build levees to protect an area from flOOding, applicable FEM A and State of Texas guidelines and the following criteria apply: L Levees shall be designed to have four feet of freeboard
above the Standard Project Flood for the fully developed watershed flows. 2. Levees shall be designed according to the Corps of Engineers design criteria whether or not they are federally
authorized levees. 42 
3. Levee systems shall be designed with interior drainage systems to prevent flooding from local runoff contained within the system for the lOO-year design flood. 4. Levee systems shall
have written operation procedures that address gate closure conditions and emergency warning plan. A copy of these procedures shall be furnished to the City Engineer and the Director
of Public Works. 5. Automated gate closure systems shall have power from two independent sources and shall be capable of being operated manually. 6. Ring levees protecting individual
structures proposed for construction after the enactment date of this ordinance shall not be permitted. 7. All new levee systems shall have permanent posItive closures to the required
design elevation. Temporary closures involving sandbagging or other procedures requiring manual operations shall not be permitted. S. Provisions shall be made for ensuring the permanent
maintenance of levees either by a flood control district or similar governmental organization or by the existing property Owner and all future owners! heirs, or assigns. 9. Additional
plan requirements include water surface profiles for the design flood and SPF; top of levee profile, definition of interior drainage facilities, including pump station and ponding areas;
location of gravity outlets, gatewells and closure structures; and elevation-duration data on the receiving system. SECTION D. Detention and Retention Facilities As previously described
in Article 5 of this ordinance, runoff rates for all land uses shall be limited to the rates that would be produced from single family residential areas. This requirement also applies
to the development of sites as churches, schools, and other institutional uses. Detention/retention facilities to reduce runoff rates will be provided within approved levee districts
unless the District can demonstrate, with technical data, that adequate detention/retention storage is provided in dedicated sumps and storage areas to offset the impacts of developments
to runoff rates equal to a single-family residential rate. Detention/retention facilities shall be designed for the lOO-year design flood according to the following criteria. 1. The
minimum amount of storage volume of the detention basin shall be that volume required to reduce runoff rate to a single-family rate. Dedicated detention/retention basins shall also include
an additional one foot of freeboard and two reet of sediment storage. The volume of runoff storage for drainage areas greater than 160 acres shall be computed using unit hydrograph procedures.
Acceptable unit hydrograph procedures include the Soil Conservation Service Dimensionless Unit Hydrograph and Snyder's Unit Hydrograph. Manual methods or use of the computer programs
TR20, HEC-l. and NUDALLAS are allowed for runoff hydrograph computation and flood routings. For drainage areas less than 160 acres, the above methods are recommended; however, an approximate
routing method based on the rational formula is allowable, as outlined in Figure 24. 2. Detention Detention areas in parking lots shall not be; In required parking spaces but in extra
spaces. Behind speed bumps unless the speed bumps are made with reinforced concrete. 43 
Deeper than six inchesunless warning signs are posted. 3. Drainage easements shall be provided for all regional detention/retention facilities and for other detention/retention facilities where two or more
owners are involved. 4. Detention/retention facilities shall be designed to empty in Jess than 24 hours, unless it is also serving as an erosion control facility. 5. Detention/retention
facilities shall not be counted as an erosion control technique unless (1) the basins are designed to empty a minimum of 24 hours from the storm event and (2) adequate sediment storage
areas in the basin have been set aside and are maintained. Other municipal ordinances give additional details as to how to design mUlti-purpose detention/retention facilities. 6. Detention/retention
facilities shall be maintained by the owner unless the facilities are dedicated to the City of Carrollton. SECTIONE. Flumes The use of flumes is not recommended for widespread use. Flumes
shall not be permitted when the purpose of a permanent flume is to carry runoff down the sides of earthen channels. A flume may be used to direct overflow runoff along property lines
until the runoff can be intercepted by streets or conduit flows. Flumes crossing sidewalks shall be covered or bridged such as to minimize danger to pedestrians. SECTIONF. Connections
from Buildings to Storm Sewers Drainage from residential areas, such as roof tops, should be allowed to flow overland before joining the storm sewer system. Seepage into basements or
sub-surface structures that is pumped to ground level, seepage from springs, and runoff from roof drains on non-residential buildings that would flow onto or across driveways, sidewalks,
or other areas commonly crossed by pedestrians can create hazards or nuisances to pedestrians. Thus, if hazards or nuisances would be created, the basement and rooftop drains shall be
tied directly to the nearest storm sewer, provided that pumped lines from basements have back flow prevenrers and the water is uncontaminated. 44 
ARTICLES FLOODPLAIN GUIDELINES SECTION A. Lands to Wblch This Article Applies A peISon shall comply with the requirements of this article for floodplain areas before making substantial
improvements to or increasing the outside dimensions of an existing structure or developing land within the design flood line of a creek or stream having a contributing drainage area
of 160 acres or more, whether or not the land has been fonnally designated as a floodplain. Hoodplain areas shall also include all areas inundated by the design flood and shown as Areas
of Special Hood Hazard on the Hood Insurance Study's maps. SECTION B. General Floodplain Regulations 1. Permitted Uses of Hoodplain Areas To minimize possible losses of life and property,
the following uses are permitted in a floodplain area provided they are also permitted in the underlying zoning district: Fann or ranch; Local utilities, electrical substation, water
reservoir or pumping station, and water treatment plant; Public park or playground, private recreation club or area, private community center, and golf course; Outside commercial amusement
approved by a specific use permit; Helistop approved by a specific USe pennit; and Radio, television, or microwave tower, and amateur communications tower with a special use permi 1.
Structures customarily associated with the above uses may be constructed within a floodplain area only if the proposed structure meets the same engineering requirements applicable to
filling in a floodplain (See Article 8.C). Open private recreation clubs or areas and private community centeIS, without exterior walls which would incur structural damage during flood
conditions, are permitted in floodplain areas. Private facUities listed above, with enclosed walls that would incur damage, are not pennitted in floodplain areas. Uses and structures
other than those mentioned above shall not be permitted in floodplain areas. 2. Residential Construction New construction in reclaimed floodplain areas and "substantial improvements"
of any eKisting residential structure in floodplain areas shall have the lowest floor, including 45 
basements or fully enclosed areas of any new or 'substantial improvement' construction, elevated to at least two feet above the design flood elevation. Fill elevations shall be one foot
above the elevation of the design flood. Incremental improvements, either at one time or over a period of time, the cumulative cost of which equals or exceeds 50 percent of the market
value at the time of the first improvement, shall be considered as a 'substantial improvement.' New residential structures or "substantial improvements' on stilts or behind ring levees
serving individual lots shall not be permitted. Improvements to an existing structure that increase the outside dimensions, but do not result in a 'substantial improvement: must meet
the requirements of Article S.C. Table 10 presents a synopsis of the requirements for residential construction in flOOdplain areas. 3. Non-r:esidential Construction New construction
in reclaimed floodplain arcas and 'substantial improvement' of any existing commercial, industrial, or or other non-residential structure in floodplain areas shall either have the lowest
floor, including basements of any new or "substantial improvement' construction, elevated to at least two feet above the design flood elevation; or, together with attendant utility and
sanitary facilities, shall: Be floodproofed so that below two feet above the design flood elevation the structure is watertight, with walls substantially impermeable to the passage ofwater;
Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and Be certified by a registered professional engineer or architect that the
standards of this subsection are satisfied. Such certifications shall be provided to the official set forth in Article 4, Section A!. Incremental improvements, either at one time or
over a period of time, the cumulative cost of which equals or exceeds 50 percent of the market value at the time of the first improvement, shaH be considered as a 'substantial improvement."
Improvements to an existing commercial, industrial or other non-residential structure that increase the outside dimensions, but do not result in a 'substantial improvement,' must meet
the requirements of Article S.c. Table 10 presents a synopsis of the requirements for nonresidential structures in floodplain areas. 4. Manufactured Homes a. All manufactured homes shall
be anchored to resist flotation, collapse, or lateral movement by providing over-the-top and frame ties to ground anchors. Special requirements shall be that: Over-the-top ties be provided
at each of the four corners of the manufactured home, with two additional ties per side at intermediate locations, with manufactured homes less than 50 feet long requiring one additional
tie per side; 46 
Frame ties be provided at each corner of the home with five additional ties per side at intermediate pOints, with manufactured homes less than 50 feet long requiring four additional
ties per side; All components of the anchoring system be capable of carrying a force of 4,800 pounds; and, Any additions to the manufactured home be similarly anchored. b. For all new
manufactured homes, new manufactured home parks and manufactured home subdivisions; for expansions to existing manufactured home parks and manufactured home subdivisions; for existing
manufactured home parks and manufactured home subdivisions where the repair, reconstruction or improvement of the streets, utilities and pads is planned; and for manufactured homes not
placed in a manufactured home park Or manufactured home subdivision; for new manufactured homes moved into an old site in an existing manufactured home park; and for substantial improvements
to a manufactured home, require that: Stands or lots are elevated on compacted fill so that the lowest floor of the manufactured home will be at least two feet above the design flood
elevation; Adequate surface drainage and access for a hauler are provided; and, No new manufactured homes shall be placed in a floodplain, except on a pad site created by compacted fill
in an existing manufactured home park, in which the new fill pad site is elevated to the design flood elevation. Manufactured homes may be supported to the required 2 feet above the
design flood elevation by stands or foundation features as accepted by FEMA Table 10 overviews the requirements for placing manufactured homes in flood hazard areas. 5. Recreation Vehicles
Recreational vehicles located on a site within a designated flOOdplain area shall (1) be on the site for fewer than 180 consecutive days and (ii) be fully licenses and ready for highway
use, or (iii) meet the elevation and anchoring requirements for 'manufactured homes' outlined in this section. A recreational vehicle is ready for highway use if it is on its wheels
or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions. 6. Streets, Parking Lots, and Bridges
The top of curb of all new streets to be built in reclaimed floodplain areas shall be at least one foot above the design flood elevation. The low beam of all new bridges to be constructed
across floodplains shall be a minimum of one foot above the design flood elevation. All new private bridges to individual homes shall have their low beams at one foot above the design
flood elevation. Parking lots associated with residential, commercial and industrial uses in reclaimed floodplain areas shall be at least at the design flood elevation. Parking lots
for 47 
public parks or playgrounds, private recreation club or area, private community center and golf courses may be located below the design flood elevation. 7. Utilities All new and replacement
water supply systems, sanitary sewer facilities, and other public utilities shall be designed to minimize or eliminate flood damage and infiltration of flood waters into the system.
8. Fences Fences (Private and Public Screening) shall be constructed such that blockage of surface water flow does not occur. Fences shall not be allowed in floodplain area or within
dedicated casements. This includes tbe requirement tbat erosive conditions shall not be created around, under or near a fence structure. 9. Additional Construction Standards for Structures
All improvements and construction permitted in a floodplain area must comply with the following requirements: a. Structures must be securely anchored to tbe foundation to prevent flotation
and collapse during inundation and designed to prevent damage to nonstructural elements during inundation. b. Thermal insulation used below the first floor elevation must be of a type
that does not absorb water. c. Adhesives must have a bonding strength that is unaffected by inundation. d. Doors and all wood trim must be sealed with a waterproof paint or similar prOduct.
e. MeChanical, electrical, and utility equipment sball be located above the design flood elevation. Water heaters, furnaces, electrical distribution panelS, and other critical mechanical
or electrical installations must not be placed in basements. Electrical circuits for basements shall be separate from circuits serving floors above the basement, and circuits for basements
shall be installed lowered from above. f. Basements are permitted for non-residential structures only if tbey are designed to preclude inundation by the design flood elevation, either
by: 1. The elimination ofexterior openings below the design flood elevation; or 2. The use of water-tight closures, such as bulkheads and flood shields. However, no basements are are
permitted in soils whose permeabiltty meets or exceeds the minimum local standards of permeability established for the installation of individual sewage disposal systems. g. Plywood
used at or below the lowest floor elevation must be of an "exterior" or "marine" grade and of a water-resistant or waterproof variety. 
h. Wood flooring used at Or below the lowest floor elevation must be installed to accommodate a lateral expansion of the flooring, perpendicular to the flooring grain, without incurring
structural damage to the building. i. Basement ceilings for non-residential structures must be of sufficient wet strength and be so installed as to survive inundation. j. Paints or other
finishes used at or below the lowest floor elevation must be capable of surviving inundation. k. All air ducts, large pipes and storage tanks lceated at or below the lowest floor elevation
must be firmly anchored to prevent flotation. I. Tanks must be vented at a location above the design flood elevation. SECTION C. Floodplain Alterations As stated previously in Article
8, Section B, no new construction is allowed in floodplain areas, but construction is allowed in those areas that can be reclaimed from the floodplain. The City of Carrollton has adopted
a "natural floodway' thaI differs from the "regulatory floodway' established by FEMA. The The 'natural floodway' consists of the natural channel and floodplain that is effective in conveying
the design flood. Areas of ineffective flow around bridges, topographiC constrictions, and other constrictions are excluded from the 'natural floodway.' The effective flow area and limits
of the 'natural floodway' are determined using 4:1 flow expansions downstream of constrictions and 1:1 flow expansions upstream of constrictions. Figure 25 displays an example ofeffective
flow areas at a typical bridge location. A Floodplain Alteration Permit for flOodplain reclamation or other types of alterations shall be allowed only ifall of the following criteria
are met: 1. Alterations of the floodplain and 'natural flOOdway' shall not increase the water surface elevation otthe design flood of the creek. 2. Alterations shall be in compliance
with FEMA guidelines. 3. Alterations of the floodplain shall not create an erosive water velocity on or off-site. 4. Alterations of the floodplain shall not significantly increase increase
downstream discharges. 5. Alterations within the CDC Regulatory Zone shall be in compliance with Article 9 of this Ordinance. 6. The effects of existing improvements or public and private
improvements for which a future commitment has been made by the City of Carrollton or county, state, or federal agencies, shall be used in determining water surface elevations and velocities.
7. Any alteration of floodplain areas shall not cause any additional expense in any current or projected public improvements. 8. The floodplain shall be altered only to the extent permitted
by equal conveyance on both sides of the natural channel. The right of equal conveyance applies to all owners and uses, including greenbelt, park areas, and recreational usages. Owners
may relinquish their right to equal conveyance by providing a written agreement to the City of Carrollton. 49 
9. Maximum slopes of filled areas shall not exceed three to one. Slopes of any excavated areas not in rock shall not exceed four to one. Fill slopes, vertical walls, terracing, and other
slope treatments may be considered provided no unbalancing ofstream flow results and only as a part of a grading permit application. 10. A grading permit shall be required so that proper
provisions for protecting against erosion losses will be made. These criteria shall be met before a Floodplain Alteration Permit can be issued for a proposed project. Typical projects
requiring a flOodplain Alteration Permit include placing fill whether or not it actually raises the property out of the floodplain, constructing a dam, straightening channel sections,
making improvements, substantial or otherwise, to existing structures in a floodplain in which the existing outside dimensions of the structure are increased, and temporary storage of
fill materials, supplies, and equipment. The required submittals for a Floodplain Alteration Permit are listed in Article 4, Section D.2. In general, the information needed for the application
can be obtained by running a backwater model, such as 􀁈􀁅􀁃􀁾􀀲􀀬􀀠and a flood routing model, such as 1R-20 or HEC-1. Both models shall be run by permit applicants. The backwater information
shall be used to determine that upstream water surface elevations and erosive velocities have not increased. Starting water surface conditions for backwater calculations are outlined
in Article 7, Section A,2. Flood routing information shall be used to insure that the cumulative effects of the reduction in floodplain storage of flood waters will not cause downstream
increases in water surface elevations and erosive velocities. Applicants can obtain copies of the existing conditions backwater models and flood routing where available from the City
Engineer. The City Engineer shall keep the models current with modifications to the floodplain. SECTION D. Verification of Floodplain Alterations. Prior to final acceptance by the City
of utilities and street construction for projects involving floodplain alterations or adjacent to defined floodplains, creeks, channels and drainageways, a certified statement shall
be prepared by a Registered Public Surveyor showing that all lot elevations, as developed within the subject project, meet or exceed the required minimum finished floor elevations shown
on the final plat of the subdivision. This certification shall be filed with the City Engineer. In addition, at any time in the future when a building permit is desired for existing
platted property which is subject to flOOding or carries a specified or recorded minimum finished floor elevation, a Registered Public Surveyor shall survey the property prior to obtaining
a building permit. The certified survey data showing the property to be at or above the specified elevation shall be furnished to the City Engineer for approval. Certificate of compliance
with the provisions of this ordinance pertaining to speCified finished floor elevations shall shall be required. The owner/developer shall furniSh, at his expense, to the City Engineer
sufficient engineering information to confirm that the minimum floor elevations proposed are as required by this paragraph. Construction permits will not be issued until (1) a conditionallctter
of map revision or amendment has been issued by FEMA, and (2) lots and/or sites are certified by a Registered Public Surveyor and are elevated from the floodplain according to the FEMA-approved
revisions to the floodplain and the requirements of this ordinance. 50 
ARTICLE 9 SPECIAL PROVISIONS TRINITY RIVER CORRIDOR DEVELOPMENT CERTIFICATE PROCESS SECTION A. Trinity River Corridor Int_docal Agreement This article recognizes the interlocal agreement
effective January I, 1990, between cities and counties which acknowledge the Trinity River Corridor, herein referred to as the Corridor, is a unique regional resource. Local governments
are responsible for the overall health, safety, and welfare of their citizens and must take the lead as stewards of the Corridor. Actions of upstream and downstream communities within
the Corridor directly effect each other such that individual local goals for floodplain management, transportation, greenway, waste management, conservation, and development can only
be achieved through cooperative management of the Corridor. SECTION B. Trinity River Corridor Area The Corridor is defined as the bed and the banks of the river segments from the dams
of Lewisville Lake, Grapevine Lake. Lake Worth, Benbrook Lake. Lake Arlington, and Mountain Creek Lake downstream to the point on the mainstream of the Trinity River near Post Oak Road
in southeast Dallas County, and all of the adjacent land area and all watercourses contained within the boundaries of the Corridor floodplain as designated by the lalest approved version
of the Trinity River Corridor digital map maintained by NCTCOG. SECTION C. Establishment of Devel()llmenl Permit In order to ensure adequate management of the Corridor. a unique certification
process has been developed and adopted. To distinguish it from other requirements, the development permit within the Corridor issued by the community will be referenced as a Corridor
Development Certificates (CDC). Any public or private development within the Regulatory Zone of the Trinity River Corridor must obtain a Corridor Development Certificate. The Regulatory
Zone is the area within the ultimate development IOO-year floodplain of the specified reach of the Trinity River as defined by the latest approved version of the digital Trinity River
Corridor Map -CDC Regulatory and Review Zones. The Review Zone is the area between the Regulatory Zone and the Designated boundaries of the Trinity River as defined by the latest approved
version of the digital Trinity River Corridor Map. CDC Regulatory and Review Zones. This map is maintained by NCTCOG. Any public or private development within the Regulatory Zone of
the Corridor must obtain a CDC prior to start of any development activity. unless specifically exempted as discussed below. A development activity is defined "any manmade change to improved
or unimproved real estate. including. but not limited to. buildings or other structures, mining, dredging, filling. grading, paving, excavation. or drilling operations." To assure consistency
with Texas Natural Resources Conservation Commission requirements. development activity also includes "any levee or other improvement", It is the express purpose of this cooperative
certification process to satisfy the requirements of the Federal Emergency Management Agency and the Texas Natural Resources Conservation Commission regarding city floodplain permit
actions within the Corridor and to effect close coordination with the U.S. Army Corps of Engineers (COE) and other state or federal agencies that have their own permit processes. The
CDC Process does not supersede other Local, State and Federal programs. 51 
SECITON D. putles and Responsibilities ofthe Floodplain Administrator Duties and responsibilities of the CDC/FIoodplain Administrator shall include, but are not to be limited to, the
issuance of CDC permit appltcations described in Article 9, Section C. Other responSibilities will include a complete and consistent analysis of all CDC applications to include, but
not limited to: Project Plans, Hydrologic Data, Hydraulic Data, Elevation -Storage -Discharge Data, COE Jurisdictional Review, and Erosion Control plans. More detailed descriptions of
these requirements are outlined in the CDC Manual. SECTION E. Common Permit Criteria The following common permit criteria describe a consistent design level of flood protection which
must be met for all CDC applications. ApplicatiOns for a CDC permit are required to provide sufficient detailed information to document compliance with the following criteria: 1. Hydraulic
Impacts: Project within the Regulatory Zone of the Trinity River Corridor: water surface elevationS, storage capacity, velocities, and conveyance. 2. Hydraulic Impacts: Tributary Projects
3. Cumulative Impacts 4. Design Level ofFlood Protection: for levees, fills. and structures on fill 5. Borrow Areas 6. Preservation ofAdjacent Project Storage. More detailed descriptions
of requirements are outlined in the CDC Manual. SECTION F. Exemptions from Corridor Development Certificate (CDC) If an applicant, owner, or principal(s) is able to show in writing that
a development meets any of the conditions below, it may be exempted by the community from the local CDC permit process. The applicant. owner. or principal(s) is still SUbject to specific
permit requirements as outlined in the community Storm Water and Flood Protection Ordinance and all other Local, State and Federal agency permit requirements. The written exemption will
be maintained on file by the community and will be provided to NCTCOG for the permanent records. EXEMPTIONS: 1. Ordinary maintenance and repairs ofany operational flood control structures.
2. Outllill structures and associated intake structures where the outfall has been permitted under the Federal NPDES or State TPDES program. 3. Discharge of material for backfill or
bedding for utility lines, provided there is no significant change in pre-existing bottom contours and excess material is removed to an upland disposal area. 4. Bank stabili7.ation activities.
52 
5. Property tbat is (1) completely outside the Regulatory Zone but within the Review Zone; and (2) defined or identified by city ordinance such that the property does not require the
Applicant to undergo the CDC process in the Review Zone. 6. Specific Prior Developments -The existing development projects in Section 1.5 DEFINITIONS of this Manual. VARIANCES: A variance
may be sought by any public or private development that cannot meet the established common criteria as detailed in Section 2 of the CDC Manual. A variance shall be any modification of
the literal provisions of the CDC Manual when strict enforcement of the CDC process would cause undue hardship, owing to circumstances unique to the individual property on which variance
from the process is requested. Variances may be issued for projects deemed to be in the overall regional public interesl, as determined by the Planning and Zoning Commission and meet
the variance reqUirements established in Article 4, Section F. An appeal from a determination made by the Planning and Zoning Commission may be made directly to the Court ofAppeal. SECTION
G. Approval Process The standard CDC form will be used to record the actions taken and will be sent to NCTCOG for permanent recordkeeping. Approval will be based on compliance with the
following steps. Step 1. Determination of Applicability by City Step 2. Jurisdictional Review by COE Step 3. Notice ofIntent to Process by City Step 4. Parallel COE, FEMA. TWC, and Regional
Review Step 5. Formal City Action SECTION II. Appeals Process The Applicant may seek relief from this process. Appellant relief of this permit process shall be sought from the City as
an independent permitting authority. SECTION I. Technical Updates The latest technical hydrologic and hydraulic information concerning the Corridor may be obtained by the CDC/Floodplain
Administrator of the respective communities from the North Central Texas Council of Gevernments and the U.S. Army Corps of Engineers -Fort Worth District. SECTIONJ. CDC Manual The most
recent CDC Manual shall be adopted as a part of this ordinance. The CDC Manual outlines the detailed requirements of this Article and is adopted in its entirety with the following exceptions:
53 
1. Any provisions in direct contradiction to this ordinance. 2. This ordinance does not adopt provisions of the CDC Manual and CDC mapping related to regulations and their enforcement
within the 'Review Zone' as defined in these documents. 3. The term of the CDC permit may be extended for multiple three-year periods as deemed appropriate by the City Engineer (see
CDC Manual, Page 6, 13). 4. The applicant is not required to officially file the CDC permit in the county records (see CDC Manual, Page 6). 5. The concept of equal conveyance shall not
apply in areas where the opposing side of the channel has already been developed to the maximum extent practicable as determined by the City Engineer (see CDC Manual, Page 8). 6. Levee
systems shall have a minimum of 4 feet of freeboard above the SPF elevation even if a relief system is 􀁰􀁾􀁯􀁶􀁩􀁤􀁥􀁤􀀠(see CDC Manual, Page 9). 7. All fills shall have a minimum of
1 foot of freeboard above the ultimate loo-year elevation (see CDC Manual, Page 9). 8. Resource Data and Maintenance and Operation Data are not required (see CDC Manual, Page 11) unless
specifically required by this ordinance. 9. Changes in State and Federal regulatory programs will not reqUire a re-evaluation or reapplication (see CDC Manual, Page 13) unless: a) construction
on the project has not begun or; b) until the term of the current permit or extension expires. 54 
ARTICLE 10 STORM WATER DISCHARGES FROM CONSTRUCTION ACTIVITIES SECTION A. General Requirements 1. All operators of construction sites shall use best management practices to control and
reduce the discharge, to the MS4 and to waters of the United States, of sediment, silt. earth, soil and other material associated with the clearing. grading. excavation, and other construction
activities to the maximum extent practicable under the circumstances. Such best management practices shall include, but not be limited to, the following measures as appropriate: a. Ensuring
that existing vegetation is preserved where feasible and thatdisturbed portions of the site are stabilized as soon as practicable in portions of the site where construction activities have temporarily or permanently ceased. Stabilization measures
may include: temporary seeding. permanent seeding. mulching. geotextiles, sod stabilization, vegetative buffer strips, protection of trees, preservation of mature vegetation, and other
appropriate measures. measures. Contractor shall submit, as a part of the Best Management Practices, a plan indicating the phaSing ofsite clearing/grading; b. Use of structural practices
to divert flows from exposed soils, store flows, or otherwise limit runoff and the discharge of pollutant from the site to the extent feasible; c. Minimization of the tracking ofsediments
off-site by vehicles, the generation of dust, and the escape of other windblown waste from the site; d. Prevention of the discharge of building materials. including cement, lime, concrete,
and mortar, to the MS4 or waters of the United States; e. Providing general good housekeeping measures to prevent and contain spills of paints, solvents, fuels. septiC waste, and other
hazardous chemicals and pollutants associated with construction, and to assure proper cleanup and disposal of any such spills in compliance with state. federal, and local requirements;
f. Implementation of proper waste disposal and waste management teChniques, including covering waste materials materials and minimizing ground contact with hazardous chemicals and trash;
g. Timely maintenance of vegetation, erosion and sediment control measures, and other best management practices in good and effective operating conditions; and h. Installation of structural
measures during the construction process to control pollutants in storm water discharges that will occur after construction operations have been completed. Structural measures should
be placed on upland soils !O the degree attainable. Such installed structural measures may include, but not be limited to. the following; storm water detention structures (including
wet ponds); storm water retention structures; flow attenuation by use of open vegetative swales and natural depressions; other velocity dissipation devices; infiltration of runoff on
site; and sequential systems which combine several practices. Operators of construction sites are only responsible for the installation and maintenance of storm water management measures
prior to final stabilization of the site, and for a period of rwo years after final acceptance by the City unless the area is disturbed by new owners. i. The owner will escrow 100% of
the cost to provide final stabilization to the site. This escrow shall be held for a period of two years from the date of final acceptance. The deposit of an 55 
escrow amount shall not relieve the owner/operator of their responsibility to stabilize the site and remain in conformance with this ordinance and other corresponding regulations. The
City shall use the escrow only if the owner/operator fails to stabilize the site in a timely manner. j. For common drainage locations that serve an area with 10 or more disturbed acres
at one time, a temporary (or permanent) sediment basin providing 3,600 cubic feet of storage per acre drained, or equivalent control measures, shall be provided where attainable until
final stabilization of the site. The 3,600 cubic feet of storage area per acre drained does not apply to flows from offsite areas and flows from onsite areas that are either undisturbed
or have undergone final stabilization where such flows are diverted around both the disturbed area and the sediment basin. For drainage locations which serve 10 or more disturbed acres
at one time and where a temporary sediment basin providing 3,600 cubic feet ofstorage per acre drained, or equivalent controls is nOl attainable, smaller sediment basins and/or sediment
traps should be used. At a minimum, silt fences, or equivalent sediment controls are required for all sideslopes and downslope boundaries of the construction area. 2. Stabilization measures
shall be initiated as soon as practicable in portions of the site where construction activities have temporarily or permanently ceased, but in no case more than 14 days after the construction
activity in that portion of the site has temporarily or permanently ceased. a. Where the initiation of stabilization measures by the 14th day afier construction activity temporary or
permanently cease is precluded bY snow cover, stabilization measures shall be initiated as soon as practicable. b. Where construction activity will resume on a portion of the site within
21 days from when activities ceased, (e.g. the total time period that construction activity is temporarily ceased is less than 21 days) then stabilization measures do not have to be
initiated on that portion of site by the 14th day after construction activity temporarily ceased. 3. Qualified personnel (provided by the operator of the construction site) shall inspect
disturbed areas of any construction site that have not been finally stabilized, areas used for stOrage of materials that are exposed to precipitation. structural control measures, and
locations where vehicles enter or exit the site, at least once every seven calendar days and within 24 hours of the end of a storm that is 0.5 inches or greater. All erosion and sediment
control measures and other identified best management practices shall be observed in order to ensure that they are operating correctly and are effective in preventing significant impacts
to receiving waters and the MS4. Based on the results of the inspection, best management practices shall be revised as appropriate, and as soon as is practicable. 4. The City Engineer
requires any plans and specifications that are prepared for the construction of site improvements to illustrate and describe the best management practices required by paragraph Al above
that will be implemented at the construction site. The City may deny approval of any building permit, grading permit, site development plan, or any other City approval necessary to commence
or continue construction, or to assume occupancy, on the grounds that the management practices described in the plans or observed upon a site inspection by the City Engineer or his representative
are determined not to control and reduce the discharge of sediment, silt, earth, soil, and other materials associated with clearing, grading, excavation, and other construction activities
to the maximum extent practicable. 5. Any owner of a site of construction activity, whether or not he/she is an operator, is jointly and severally responsible for compliance with the
reqUirements in this Section A 6. Any contractor or subcontractor on a site of construction activity, who is not an owner or operator, but who is responsible under his/her contract or
subcontract for implementing a best management 56 
practices control measure. is jointly and severally responsible for any willful or negligent failure on hislher part to adequately implement that control meaSUre if such failure causes
or contributes to causing the City to violate a water quality standard or any State-issued discharge permit or discharges from its MS4. SECTION B. Five-Acre Disturbances All operators
ofsites of construction activity. including clearing, grading, and excavation activities, that result in the disturbance of five or more acres of total land area shaH comply with the
following requirements in addition to those in section A: 1. Any operator who intends to obtain coverage for storm water discharges from a construction site under the NPDES General Permit
for Storm Water Discharges From Construction Sites ("the Construction General Permit") shall submit a signed copy of its Notice of Intent (NOI) to the City Engineer at least two (2)
days prior to the commencement of conStruction activities. If the construction activity is already underway upon the effective date of this Ordinance, the NOI shall be submitted within
thirty (30) days. For storm water discharges from construction dates where the operator changes, an NOI shall be submitted at least (2) days prior to when the operator commences work
at the site. 2. A Storm Water Pollution Prevention Plan (SWPPP) shall be prepared and implemented in accordance with the requirements of the Construction General Permit or any individual
or group NPDES permit issued for storm water discharges from the construction site, and with any additional reqUirement imposed by or under this Ordinance and any other city ordinance.
The SWPPP shall be submitted with the engineering plans for the proposed site improvements. 3. The SWPPP shall be prepared, signed, and sealed by a Registered Professional Engineer or
Registered Landscape Architect. The signature and seal of the Registered Professional Engineer or Registered Landscape Architect shall constitute hislher attestation that the SWPPP fully
complies with the requirements of the Construction General Permit. or with any applicable individual or group NPDES permit issued for storm water discharges {rom the construction site,
and with any additional requirement imposed by or under this Ordinance. The SWPPP shall contain the name, title, and business address of the Registered Professional Engineer or Registered
Landscape Architect Signing it, and the date he/she does so. 4. The SWPPP shall be completed prior to the submittal of the NOI to the City Engineer and, for new construction, during
the plan review process with the site development plans. The SWPPP shall be updated and modified as appropriate and as required by the Construction General Permit and this Ordinance.
(Any update or modification to the SWPPP shall be prepared, signed, and sealed by a Registered Professional Engineer or Registered Landscape Architect, if the Original SWPPP was required
by paragraph B.3 to have been prepared by a Registered Professional Engineer or Registered Landscape Architect). 5. A copy of any NOI that is required by paragraph B.1 shall be submitted
to the City in conjunction with any application for a building permit. grading permit. site development plan approval. and other City approval necessary to commence or continue construction
at the site. 6. The City Engineer may require any operator who is required by paragraph B.2 to prepare a SWPPP to submit the SWPPP, and any modifications thereto, to the City Engineer
for review. Such submittal and review of the SWPPP may be required by the City Engineer prior to commencement of or during construction activities a t the site. 57 
7. Upon the City Engineer's review of the SWPPP and any site inspection that he/she may conduct, the City may deny approval of any building permit, grading permit, site development plan,
or any other City approval necessary to commence Or continue construction, or to assume occupancy, on the grounds that the SWPPP does not comply with the requirements of the Construction
General Permit, any individual or group NPDES permit issued for storm water discharge from the construction site, or any additional requirement imposed by or under this Ordinance. Also,
if at any time the City Engineer determines that the SWPPP is not being fully implemented, the City may similarly deny approval of any building permit, grading permit, site development
plan or any other City approval necessary to commence or continue construction, or to assume occupancy, at the site. 8. Any significant modification to the SWPPP for a site shall be
prepared, signed, and sealed by a Registered Professional Engineer or Registered Landscape Architect as required for the original SWPPP by paragraph B.3. 9. All contractors and subcontractors
identified in an SWPPP shall sign a copy of the following certification statement before conducting any professional service identified in the SWPPP. I certify under penalty of law that
I understand the terms and conditions of the National Pollutant Discharge Elimination System (NPDES) permit that authorizes the storm water discharges associated with the industrial
activity from the construction site identified as part of this certification, with the Storm Water and Flood Protection Ordinance of the City of Carrollton, and with those provisions
of the Storm Water Pollution Prevention Plan (SWPPP) for the construction site for which I am responSible. The certification must include the name and title of the person providing the
signature; the name, address, and telephone number of the contracting firm; the address (or other identifying description) of the site; and the date the certification is made. 10. The
SWPPP, SWPPP, with the Registered Professional Engineer's or Registered Landscape Architect's signature and seal affIXed, and the certifications of contractors and subcontractors required
by paragraph B.9, and with any modifications attaChed, shall be retained at the construction site from the date of commencement ofconstruction through the date of final stabilization.
11. The operator shall make the SWPPP and any modification thereto available to the City Engineer upon request (as well as to EPA and State inspectors). 12. The City Engineer may notify
the operator at any time that the SWPPP does not meet the requirements of the Conslruction General Permit, any applicable individual or group NPDES permit issued for storm water discharges
from the construction Site, or any additional requirement imposed by or under this Ordinance. Such nOlification shall identify those provisions of the permit or Ordinance which are not
being mel by the SWPPP, and identify which provisions of the SWPPP reqUire modifications in order order 10 meet such reqUirements. Within seven (7) days of such notification from the
City Engineer or as otherwise provided by the City Engineer, the operator shall make the required changes to the SWPPP and shall submit to the City Engineer a written certifica tion
that the requested changes have been made. 13. The operator shall amend Ihe SWPPP whenever there is a change in design, construction, operation, or maintenance, which has a Significant
effect on the potential for the discharge of pollutants 10 the MS4 or to the waters of the United States, and which has not otherwise been addressed in the SWPPP, or if the SWPPP proves
to be ineffective in eliminating or significantly minimizing pollutants, or in otherwise achieving the general objective of controlling pollutants in storm water discharges associated
with construction activity. In addition, the SWPPP shall be amended to identify any new contractor and/or subcontractor that will implement a measure in the SWPPP. 58 
14. Qualified personnel (provided by the operator of the construction site) sball inspect disturbed areas of tbe construction site that have not been finally stabilized, areas used for
stOrage of materials tbat are exposed to precipitation, structural control measures, and locations where vehicles enter or exit the site, at least once every seven calendar days and
within 24 hours of tbe end of the storm that is 0.5 inches or greater. Disturbed areas and areas used for storage of materials that are exposed to preCipitation shall be inspected for
evidence of, Or the potential for, pollutants entering the drainage system. Erosion and sediment control measures identified in the SWPPP shall be observed to ensure that they are operating
correctly. Where discharge locations or points are accessible, they shall be inspected to ascertain whether erosion control measures are effective in preventing significant impacts to
receiving waters or the MS4. Locations where vehicles enter or exit the site shall be inspected for evidence of off-site sediment tracking. 15. In case of emergency, City forces will
perform corrections and deduct their cost from the escrow account. 16. Based on the results of the inspections required by paragraph B.14, the site description and/or the pollution prevention
measures identified in the SWPPP shall be revised as appropriate, but in no case later than seven calendar days following the inspection. Such modifications shall provide for timely
implementation of any Changes to the SWPPP within seven calendar days following the inspection. 17. A report summarizing the scope of any inspection reqUired by paragraph B.14, and the
name(s) and qualifications of personnel making the inspection, the date(s) of the inspection. major observations relating to the implementation of the SWPPP, and actions taken in accordance
with paragraph B.lS above shall be made and retained as part of the SWPPP for at least three years from the date that the site is finally stabilized. Such report shall identify any incidence
of noncompliance. Where a report dos not identify any incidence of noncompliance, tbe report shall contain a certification that the facility is in compliance with the SWPPP, the facility's
NPDES permit, and this Ordinance. The report shall be certified and signed by the person responSible for making the report. 18. The operator shall retain copies of any SWPPP and all
reports required by this Ordinance or by the NPDES permit for the Site, and records of all data used to complete the Nor, for a period of at least three years from the date that the
sire is finally stabilized. 19. Where a site has been finally stabilized and all storm water discharges from construction activities that are authorized by this Ordinance and by the
NPDES permit for those construction activities are eliminated, or where the operator of all storm water discharges at a facility changes, the operator of the construction site shall
submit to the City Engineer a Notice of Termination (NOl) that includes the information required for Notices of Termination by Part VIII of the Construction General Permit. 20. Upon
final stabilization of the construction site, the owner (or the duly authorized representative thereot) shall submit written certification to the City Engineer that the site has been
finally stabilized. The City may withhold an occupancy or use permit for any premises constructed on the site until such certification of final stabilization has been filed and the City
Engineer has determined, following any appropriate inspection, that final stabilization has. in fact, occurred and that any reqUired permanent structural controls have been completed.
59 
TABLEl VALUES OF 'C' FOR USE IN 'RATIONAL METIIOD" FORMULA O' -􀁃􀁾􀁉􀁁􀀠Flat 0% to 1% Moderate 1% to 3.5% Steep 3.5% and over Land Use from Master Plan Park areas· No developed land
Developed Park sites Single Family Residential Duplex Multiple Family Schools" Churches" Local Business Central Business Commercial Industrial Park areas· No developed land Developed
Park sites Single Family Residential Duplex Multiple Family Schools" Churches" Local Business Central Business Commercial Industrial Park areas -No developed land Developed Park sites
Single Family Residential Duplex Multiple Family Schools" Churches" Local Business Central Business Commercial Industrial Value of 'CO (Runolf Coefficient) 0.20 0.30 0.45 0.50 0.55 0.60
0.70 0.65 0.80 0.80 0.75 0.30 0.40 0.55 0.60 0.70 0.70 0.75 0.70 0.85 0.85 0.80 0.35 0.45 0.65 0.70 0.80 0.80 0.85 0.90 0.90 0.90 0.90 • Values for C in the rational method shall be
LO for the 10 year event and 1.25 for the 100 year storm event. f •• Schools and Churches may support alternate "C' values based on specific site plans . 60 
TABLE 2 AVERAGE VELOCITY FOR USE IN DETERMINING TIME OF COt'CEN1RATION 0% to 3% 4% to 7% 8%1011% Over 12% Description of V. in V.in V. in V.in Water Course f.p.s. f.p.s. f.p.s. f.p.s.
Surface Drainage Channels Slorm Sewers 5 9 13 15 Determine V. by Manning's Equation Determine V. by Manning's Equation TABLE 3 MINIMUM SLOPES FOR CONCRETE PIPES (to produce a velocity
of2.5 f.p.s. Or greater) (n = .013) Pipe Diameter Slope (inches) (Feet!l00 Feet) 18 21 24 27 30 33 36 39 42 45 48 .180 .150 .120 .110 .090 .080 .070 .062 .056 .052 .048 Pipe Diameter
Slope (inches) (Feet!l00 Feet) 51 .045 54 .041 60 .036 66 .032 72 .028 78 .025 84 .023 90 .021 96 .019 102 .018 lOS .016 61 
TABLE 4 MAXIMUM VELOCITIES IN CONDUITS FLOWING FULL AND CHANNELS Maximum Velocity Flow Through: (fps) Culverts 12.5 Inlet Laterals 10 Storm Sewers 12.5 Earthen Channels See Table 11
Concrete Channels 12 Shale 6 22Rock 6-10* * Depends upon exact type ofvegetative cover, soil, or rock for the location in question. TABLES ROUGHNESS COEFFICIENTS FOR CLOSED CONDUITS
Recommended Roughness Coefficient Materials of Construction "n" Concrete Pipe Storm Sewer Good Alignment, Smooth Joints .013 Fair Alignment, Ordinary Joints .015 Poor Alignment, Poor
JOints ,017 Concrete Pipe Culverts ,012 Monolithic Concrete Culverts & Conduit .012 Corrugated Metal Pipe ,024 Corrugated Metal Pipe (Smooth Lined) ,013 62 
TABLE 6 ENTRANCE LOSS COEFFIClENTS 2Vl Entrance head loss HL =Ke2g TypeofStructure and Design ofEnlr!mce 􀁾􀁃􀁯􀁮􀁣􀁲􀁥􀁴􀁥􀀠Projecting from fio. socket end (groove-end) Projecting from
fill. square cut end Headwall or headwall and wingwalls Socket end of pipe (groove-end) Square-edge Rounded (radius '" 1/12D) Mililred to conform to fill slope End·section confonning
to fill slope Beveled edges. 33.7 or 45 bevels Side-or slope-tapered inlet 􀁾or Pjpe-Arch. Comlgated Meta! Projecting from fill (no headwall) Headwall or headwall and wingwalls square-edge
Mitered to conform to fill slope, paved or unpaved slope End·section confonning to fill slope Beveled edges. 33.7 or 45 bevels Side-or slope-tapered inlet Bll!. Reinforced Concrete Headwall
parallel to embankment (no wingwalls) Square-edged on 3 edges Rounded on 3 edges to radius of 1/12 barrel dimension or beveled edges on 3 sides Wingwalls at 30 to 75 to barrel Square-edged
at crown Crown edge rounded to radius of 1/12 barrel dimension dimension. or beveled top edge Wingwall at 10 to 25 to barrel Square-edged at crown Wingwall parallel (extension of sides)
Square-edgedatcrown Side-or slope-tapered inlet Coefficient Ke 0.2 0.5 0.2 0.5 0.2 0.7 0.5 0.2 0.2 0.9 0.5 0.7 0.5 0.2 0.2 0.5 0.2 0.4 0.2 0.5 0.7 0.2 63 
TABLE 7 VELOCITY HEAD LOSS COEFFlClENIS FOR CLOSED CONDUITS MANHOLE AT CHANGE IN PIPE DIRECTION DESCRIPTION ANGLE HEAD LOSS COEFFICIENT Kj D1 􀁁􀁎􀁃􀁌􀁅􀁾....-D1=D2 D2 I I 90' 60' 45'
30' 0.55 0.48 0.42 0.30 0' 0.05 BENDS IN PIPES HEAD LOSS DESCRIPTION ANGLE COEFFICIENT Kj 90' 0.50 60' 0.43􀁁􀁎􀁇􀁕􀁾􀀠45' 0.37 30' 0.25 JUNCTION HEAD LOSS DESCRIPTION ANGLE COEFFICIENT
Kj 0' 1.00 221/2' 0.75􀁎􀀼􀁮􀁾􀀠45' 0.50 '\-"'-:t-V, V2 60' 0.35 90' 0.25 64 
TABLES ROUGHNESS COEFFICIENTS FOR OPEN CHANNELS FLOW AREAS Channel Description MINOR NATURAL STREAMS (Top Width at Flood Stage Less Than 100 Feet) Moderately Well-Defined Channel Grass
and Weeds, Little Brush Dense Weeds, Little Brush Weeds, Light Brush on Banks Weeds, Heavy Brush on Banks Weeds, Dense Willows on Banks Irregular Channel with Pools and Meanders Grass
and Weeds, Little Brush Dense Weeds, Little Brush Weeds, Light Brush on Banks Weeds, Heavy Brush on Banks Weeds, Dense Willows on Banks Floodplain, Pasture Short Grass, No Brush Tall
Grass, No Brush Floodplain, Cultivated No Crops Mature Crops Floodplain, Uncleared Heavy Weeds, Light Brush Medium to Dense Brush Trees with Flood Stage Below Branches MAJOR NATURAL
STREAMS (Top Width at Flood Stage Greater Than 100 Feet) The roughness coefficient is less than that for minor streams of similar description because banks offer less effective resistance.
Moderately Well Defined Channel Irregular Channel Roughness Coefficient Minimum Normal 0.025 0.030 0.030 0.035 0.030 0.035 0.035 0.050 0.040 0.060 0.030 0.036 0.036 0.042 0.036 0.042
0.042 0.060 0.048 0.072 0.020 0.030 0.025 0.035 0.025 0.030 0.030 0.040 0.035 0.050 0.070 0.100 0.080 0.100 0.025 0.035 Maximum 0.033 0.040 0.040 0.060 0.080 0.042 0.048 0.048 0.072
0.096 0.035 0.050 0.035 0.050 0.070 0.160 0.120 0.060 0.100 65 
TABLE S, continued Roughness Coefficient Channel Description Minimum Normal Maximum MANMADE VEGETATED CHANNELS Mowed Grass, Clay Soil 0.025 0.030 0.035 Mowed Grass, Sandy Soil, Or Easily
Erodible Soils 0.025 0.030 0.035 MANMADE NON·VEGETATED CHANNELS Clean Gravel Section 0.022 0.025 0.030 Shale 0.025 0.030 0.035 Smooth Rock 0.025 0.030 0.035 LINED CHANNELS Smooth Finished
Concrete 0.013 0,015 0.020 Riprap (Larger Pieces) 0.030 0.040 0.050 66 
TABLE9.A TEMPORARY VEGETATION Temporary Vegetation -The following plants are commonly used for temporary cover in Texas. For optimum planting dates and adaptations for a specific soil
or site, contact your local field office of the USDA, Soil Conservation Service. Planting 1 2 3 Species Rate/Acre Planting Date Source Cane, Redtop 30#!S 8/15-9/30 C Millet, German 40#/S
4/1-5/15 C Oats 3bu/S 8/15-9/30 C Panicum, Texas 2S#!S 3/15-5/15 C Prosomillet 40#!S 4/1-5/15 C Rye, Etbon 1-1/2 bu/S 8115-9130 C Ryegrass, Annual 30#!S 8/15-9/30 C Sprangletop, Green
3.4#PLS/S 211-5/15 C Sudangrass 4O#!S 4/1-5/15 C 1 Planting RatelAcre: S -# Commercial Seed/AC, bu -bushels/AC, #PLS -Pure Live SeedlAC 2 Planting Date: This represents a statewide spread
in planting dates. Refer to local guides for specific dates. 3 Source: C -Commercial 67 
TABLE9.B PERMANENTVEGETATfON -LOW AREAS Permanent Vegetation. Because ofwide variations in growing conditions within a planned area, permanent vegetation has been selected for the following
conditions. For optimum planting dates and adaptations for a specific soil or site, contact your local field office of the USDA, Soil Conservation Service. Note: Low areas are subject
to ephemeral and intermittent flows. Moisture Planting Species Tolerance1 RateJMaterials2 Source4 Bermudagrass, Coastal or Selection 3A/2 50 cu.ftlAc/Sp 12/1·5130 C Common A/2 4.6#IAc/S
3/1·5130 C Buffalograss A!3 32#/AcIS 1/1-4130 CorPMC Bushy Beard Grass C!3 Spring Cordgrass, Prairie B!2 l/sq.ft/R 1/1·5130 L Eastern Gammagrass C!3 Spring Knotgrass A/2 lIsq .ft/R&St
2/1-5130 L Marshmillet B/1 l/sq.ft/R 4/1·5130 L Reedgrass, Common A/2 l/sq.ft/R 2/1-5130 LorPMC Vine·mesquite A/2 l/sq.ft/St 2/1·1/30 L 1 Moisture Tolerance: Total Submergence Soil Saluration
A -20 days or more 1 . Require a saturated soil B-1O·20days 2· Will tolerate prolonged prolonged saturation and frequent drought. C • Less than 10 days 3 . Will not tolerate a constantly
saturated soil. 2 Planting: Rate -#PLS/AC, Plant Parts/sq.ft. Materials -S • Seed, R • Rhizomes, Sp . Sprigs, St -Stolons 3 Planting Date: This represents a statewide spread in planting
dates. Refer to local guides for specific dates. 4 Source: C -Commercial, L. Locally Collected, PMC -Plant Material Center (as available) 68 
TABLE9.C PERMANENT VEGETATION -SIDE SLOPES Species Planting RateIMaterials3 Grasses Bermudagrass. Common Selection 3 Or Coastal All All 4.6#/Ac/S 50 cu.fi/Ac/Sp 3/1·5/30 12/1-5/30 C
C Bluestem, K.R.* Old World' M·F M·F 4#/Ac/S 2.4#/Ac/S 12/1-5/30 2/1-5/30 C PMC Buffalograss' M-F 32#/Ac/S 1/1-5/15 CorPMC Dallisgrass Knotgrass1 M·F All 7#/Ac/S liSq.fiIR&St 211-5/30
2/1·5/30 C L Vine-mesquite All liSq.fi/St 2/14/30 L Wildrye All 25#/Ac/S 911-10/1 L Forbs: Busbsunflower* All 10#/Ac/S 4/1-5120 LorPMC Englemandaisy,1 All 30#/Ac/S 9/1-2/30 LorPMC Legumes:
Trailing wildbean' CoM 25#/Ac/S 2/15-5/15 LorPMC Vetch' All 2O#/Ac/S 911-1011 C 'Mixtures only: Reduce rates according 10 percentage ofmixture desired. 1 Lower portion ofslope only,
frequently inundated. 2 Soils: C -Coarse, M -Medium. F -Fine 3 Planting: Rate -#PLSlAC. Plant PartsiSq.fl. Materials -S -Seed, R -Rhizomes, Sp -Sprigs, St -Stolons 4 Planting Date: This
represents a statewide spread in planting dates. Refer to local guides for specific dates. 5 Source: C -Commercial. L -Locally Collected, PMC -Plant Material Center (as available) 69

TABLE9.D PERMANENT VEGETATION BERMS, SPOIL BANKS, AND SIMILAR AREAS Species Grasses Bermudagrass, O:lmmon Selection 3 or O:lastal Bluestem, Caucasian' K.R.' LitlIe' Buffulograss* Fescue
Hardinggrass 'Wintergreen' Indiangrass ' Kleingrass, 'Selection 75"' Wildrye* Wintergrass, Texas' Forbs: Bushsunflower* Englemandaisy' Partridgepea* Sunflower, Maximillan* Soils I All
All M-F M-F All All M-F M-F All M-F All M-F All All CoM All Planting RaieIMaterials2 4.6#/AcIS 50cu.ft/Sp 4#/AcIS 4#/M/S 6.8#/Ac/S 6#/Ac/S 20#1M/S 6#/AcIS 9#/Ac/S 4#/AcIS 3O#/Ac/S 3O#/AcIS
10#/Ac/S 3O#/Ac/S lO#/AcIS 16#IM/s 􀁐􀁬􀁡􀁮􀁴􀁩􀁾􀁧􀀠Date 3/1-5/30 12/1-5/30 12/1-5/30 12/1-5/30 2/1-5/15 211-5/15 911-10/30 911-10/30 2/1-5/30 111-5/30 911-10/1 9/1-10/30 4/1-5/30 9/1-2/30
2115-5/15 411-5/30 Source4 C C C C C C C C C C L C LorPMC LorPMC CorPMC LorPMC 70 
TABLE 9.D, continued Planting 􀁐􀁬􀁡􀁮􀁴􀁩􀁾􀁧􀀠Species SOils1 RateIMaterials2 Date Source4 Legumes: Clover, Crimson' M 20#/Ac/S 9/1-10/30 C White' M-F 3#/Ac/S C Trailing wildbean'CoM 10#/AC/S 2/15-5/15 PMC Vetch' All 20#/Ac/S 9/1-1011 C 'Mixtures only: Reduce rates according to percentage ofmix lure desired. 1 Soils: C -Coarse, M -Medium, F -Fine 2 Planting:
Rate -#PLS/AC, Plant Parts/Sq.ft MaterialS -S -Seed, R -Rhizomes, Sp -􀁓􀁰􀁲􀁩􀁧􀀮􀁾􀀬􀀠St -Stolom; 3 Planting Date: This represents a statewide spread in planting dates. Refer to local
guides for specific dates. 4 Source: C _ Commercial, L -Locally Collected, PMC -Plant Material Center (as available) 71 
TABLE 10 SYNOPSIS OFREQUlREMENTS TO PROTECf STRUcruRES FROM FLOODING Isa Is a Floodplain Is Lowest Is Floodproofing Develop Alteration Permit Floor Allowed as an ment Required? Req'dTo
Alternative to Permit Be2 Feet Lowest Floor Req'd? Above Requirement? Design Flood , Elev.?, RESIDENTIAL New Structure Yes Yes, if new structures Yes No are being placed in a proposed
floodplain reclama tion area. Substantial improvement (i.e., value of Yes Yes, if structure is Yes,of No renovation ofexisting structure is SUbject to flooding. improve-greater than
50% of the structure). ment Renovation valued at less than 50% of Floodproofing is the structure's value, with no expansion No No No allowed, but not of outside dimensions. required.
Renovation valued at less than 50% of Yes Yes, if structure is No Floodproofing is the structure's value, but including allowed, but not expansion of outside dimensions. subject to flooding.
required. ! , I 72 
TABLE 10, continued Is Lowest Is F1oodproofing Is a Floodplain Isa Alteration Permit Floor Allowed as anDevelop AItemative to ment Required? Req'dTo Be2Feet Lowest FloorPermit Above
Requirement?Req'd? Design :Flood , iElcv.? , NON-RESIDENTIAL New Structure Yes Yes, if new structures are being placed in a proposed floodplain reclamation area. Yes No Substantial improvement
(Le., value of renovation of existing structure is greater tban 50% of the structure). Yes Yes, if structure is SUbject to flOOding. Yes,of improvement Yes Renovation valued at less
than 50% of the strucrure's value, with no expansion ofoutside dimensions. No No No F1oodproofing is allowed, but not required. Renovation valued at less than 50% of the structure's
value, but including expansion ofoutside dimensions. Yes Yes, if structure is SUbject to flooding. No F1oodproofing is allowed, but not required. , I 73 
TABLE 10, continued : Is a Develop ment Permit Req'd? Is a Floodplain Alteration Permit Required? Is Lowest Floor Req'dTo Be2 Feet Above Design Flood Elev.? Is Floodproofing Allowed
as an Alternative to Lowest Floor Requirement? MANUFACI'URED HOMES New home placed at any pad site Yes Yes, ifnew structures are being placed in a proposed floodplain reclamation area.
Yes No Expansion ofan existing home park Yes Yes, if the park is in a floodplain area. Yes No New home park Yes Yes, if the new park is being located in a proposed floodplain Yes No
area. Substantial improvements to an existing manufactured home Yes Yes, if the pad site for the home is in a flood hazard area and the pad is being raised or expanded. Yes No Renovation
valued at less than 50% of the manufactured home's value, with no expansion of the home's or pad's outside dimensions. No No No No Renovation valued at less than 50% of the manufactured
home's value, but including expansion of its outside dimensions . . Yes Yes, ifstructure is SUbject to flooding. No i No 74 
TABLE 10, continued Is a Floodplain Is Lowest Is Floodprooflng Develop Is a Alteration Permit Floor Allowed as an ment Alternative to Permit Required? Req'dTo Be 2 Feet Lowest Floor
i Req'd? , Above Requirement? Design Flood Elev.? RECREATIONAL VEHICLES Recreational Vehicle which is: No NoNoNo 1. on a site less than 180 consecutive days, 2. fully licensed and ready
for higllway use, 3. has quick disconnect utilities and devices, and 4. has no permanently attached additions. Vellicle at any pad site which does not Yes, if vehicle is beingYes Yes
No meet all recreational requirements placed in a proposed flOOdplain reclamation area. Vehicles which do not meet all No recreational requirements at an Yes, if the park is in a YesYes
floodplain area. expansion ofan existing home park New home park for vehicles which do Yes, if the new park is No not meet all recreational requirements Yes Yes being located in a proposed
floodplain area. , 75 
I TABLE 11 MAXIMUM PERMISSIBLE VELOCITIES FOR CHANNELS LINED WITH GRASS PERMISSIBLE VELOCITY, FPS , COVER ISLOPE : RANGE,. Easily Eroded Soils % Bermuda Grass 0-5 6 5-10 5 >10 4 Buffalo
grass, Kentucky bluegrass 0-5 5 smooth brome, blue grama 4 >10 5-10 3 Grass mixture 0-5 4 5-10 3 Do nat use on slopes steeper than 10% Lespedeza sericea, weeping love grass, 0-5 2.5
grass, ischaemum (yellow blue-stern), Do not use on slopes steeper than 5% kudzu, alfalfa, crabgrass except for side slopes in a combination channel. Annuals -used on mild slopes or
as 0-5 2.5 temporary protection until permanent Use an slopes steeper than 5% is nat recommended. coverS are established, common lespedeza, Sudan grass Remarks: The values apply to average,
uniform stands of each rype ofcover. Use velocities exceeding 5 fps only where good covers and proper maintenance can be obtained. Based on past experience, all sails within the City
of Carrollton have been found to be easily eroded soils . • Longitudinal bed slape of the channel bottom. 76 
-CITY OF CARROLLTON RAINFALL INTENSITY VALUES 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 STORM 1 ENCY STORM DURATION (MINUTES 1 (YEARS) 􀁾􀀠:::> 0 ::t: 􀁾􀀠W 0.. (J) w ::t: <.) Z-Z >!: (J) z
OJ ..Z-...l ...l <t U. Z <t co: 5 10 15 30 60 120 180 .9 2 5.94 4.92 4.16 2.92 1.88 1.15 0.84 .8 5 6.96 S.76 4.92 3.56 2.35 1.52 1.11 0.66 10 7.68 6.42 5.44 4.02 2.68 1.79 1.31 0.79
.7 25 8.76 7.32 6.28 4.70 3.16 2.10 1.53 0.9 .6 50 9.72 8.10 6.88 5.22 3.53 2.35 1.73 1.05 100 10.50 8.82 7.52 5.74 3.90 2.61 1.91 1.17 .5 300 4005 10 15 20 30 40 50 60 100 200 RAINFALL
DURATION IN MINUTES n 
CAPACITY OF TRIANGULAR GUTTERS FIGURE 2 EXAMPLE KNOWN: SOLUTION, MAJOR THOROUGHFARE, TYPE M6D ENTER GRAPH AT .5' PAVEMENT WIDTH: 33' INTERSECT CROSS SLOPE: SIS"11' GUTTER SLOPE : 􀀲􀀮􀀰􀁾􀀠INTERSECT
GUTTER SLOPE : 􀀲􀀮􀀰􀁾􀀠 PAVEMENT CROSS SLOPE: S/S"/1' READ GUTTER CAPACITY: 23.5 c.f.s. DEPTH Of GUTTER FLOW: .5' FIND: GUTTER CAPACITY GUTTER CAPACITY IN C.F.S. 5 1 2 3 4 5 10 20
SO 40 100 '--I, , I I I I I I ' .! ,, 11II I I II Ii I ! I I II, , II i ! I ! II i , ;l' ', ' I I ! i I I ! 'I' ttl􀁾􀀠I I , : I Ii! I I II• , 􀁉􀁾􀀠! i • , I, , I i :/,. I j i l BI
.I, 11/, I ' !I : I I .::t ' I !/V: !:I /I I I ,,'. ' .J I , ! 􀀬􀁾􀀠/!, 1. i ' ! 'l /Il . '.UI :1/, , ---i 1.,\ T V 51 i ' 11': SM //'I II L //. /􀁾􀀠L ,I" II V ,. Vci 􀁬􀁾􀀠􀀮􀁾mII//FWfI
I'///iBI //II///;I I I I V //I .2.S.4 .5 Ii" Ii : , ,1 DEPTH OF GUTTER FLOW IN FEET (ROUGHNESS COEFFICIENT n : .0175) 78 
STREET WIDTH 30' 36' 50 40 HO.O' I LO.1 t:iI,ii'U) 4'. . HO.l'-l1..083'41.6' 30 ----'11.10.0' Z !-LD.2' -.1 20 tLO.4• 1::' ... 􀁾􀁧􀀧􀁡􀁾􀀠r.............. 10 Q Z; o 􀁾􀀠UJ 110:11/.......
.. .... '""' 11.1 11.1 (,I'" iii :;:) (,I ! 􀁾􀀠EXAMPLE: KNOWN: RESIDENTIAL STREET. PAVEMENT WIDTH: 30' GUTTER SLOPE: 1.0" GUTTER DIFFERENCE: 0." FIND: GUTTER CAPACITY OF HIGH CURB .............
GUTTER CAPACITY OF LOW CURB '""' .... 􀁾􀀠􀁓􀁏􀁌􀁕􀁔􀁉􀁏􀁾􀀠-..gFROM 0.6'''ON T-l!,E HIGH CURB PROJECT HORIZON A LLY TO""HE PJVOT LINE. FROM THE !!'i ........ PIVOT LINE DRAW A STRAIGHT.J,INE
TO 􀁾􀀠GUTTER SLOPE: 1.0,. ................. III READ Q: 0.69 c.I•• , FOR HIGH CURB .....----....... is'" 􀁓􀂷􀀭􀀭􀀭􀀭􀀭􀀻􀀻􀁾􀁍􀀻􀀺􀀭􀀻􀀺􀁾􀀻􀀻􀀭􀁮􀁲􀁥􀀭LOW CURBPROJEC;-= -7:::: ..
HORIZONALLY TO THE PIVOTJ.INE., FROM THE< (,I PIVOT LINE DRAW A.STRAIGHf LINE TO GUTTER SLOP!! : 1.0" READ Q: 5.9. c.I••. FOR LOW CURB CAPACITY OF PARABOLIC GUTTERS (30'& 36' STREET
WIDTHS) FIGURE 3 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0. 2,0 1,0 0.9 0.8 0.7 . !1.6 0.5 0.4 MIN. HO.2' HO.3' ..... HO.41.0 HO.S' MO.6' HO.7' MO.8' HO.83· MAX ____HO_._2:1LO.1•O• .. __􀁾􀁈􀁾􀀰􀁟􀀮􀀴􀁾􀁾􀁉􀀠
______ HO.6' ---HIIO.8'---/-L ;IFFERENCE ....................... 8 , 5 4 3 2 1 􀀭􀀭􀀭􀁾􀀠0.6 0.5 0.4 O.S 0.2 0.1 ....􀁾􀀠
STREET WIDTH 40' 44' .. I---I---0:6' i-'i..O.2' LO.2'--I 8.!t' ::1:8:;;· 1;;;'3:--1010.2', sA.!,. LlO' -1010.4' : Ho.i-------------HO.!!', , ,-HI.O· 50 40 30 '" Z 20Ho.O to! ::; I-0___
.'" HO.2 :> -ii: 8 6 Ho.4''. 5 4 '00 o 1010.8 , r --_.....-------3 2 1HO.8.0.8 0.6 0.5 0.4 H 1.0' 0.3 0.2 0.1 􀁾􀀺􀀢􀀬􀀡􀂷􀀺􀁾􀀼􀁩􀀺􀀺􀀺􀀮􀀺􀀠􀀮􀁾􀀮􀀠􀁾􀀢􀀧􀀺􀀠􀀺􀁾.."..;:;, :;',: 0;..
.. •􀁾􀀢􀀻􀀧􀀢􀁬􀀮􀂷􀀠••􀁾􀀭􀁾􀀢􀁪􀀻􀀺􀁾􀀠..􀁾􀀺􀁦􀀠DIFFERENCE 10.0 9.0 8.0EXAMPLE: 7.0 KNOWN, 6.0 COLLECTOR STREET, PAVEMENT WIDTH: 40' I-r-5.0 o ... z GUTTER SLOPE: 2.m!> ... o II.
\-4.0 U.___ GUTTER DIFFERENCE: 0.6' '"(/) -FIND:,_......... '" '" 􀁾􀀠II: II: 3.0GUTTER CAPACITY OF HIGH CURB '" "" GUTTER CAPACITY OF LOW CURB_ '" "" I-...-....--..... w'" SOLUTION:
-........... III '" -------FROM 0.6' ON THE HIGH CURB PROJECT ___"'::I.wIi-2.0 u Z HORIZONALL Y TO THE PIVOT LINE. FROM THE -::;) '" PIVOT LINE DRAW A STRAIGHT LINE TO '" U 0 "" ...
-Z GUTTER SLOPE: 2.0" READ Q: 2.4 c.l••. FOR HIGH CURB "' i: 1.0u FftOMO.6'ON THE LOW CURB PROJECT "" 0.9 HORIZONALLY TO THE PIVOT LINE. FROM THE <C <C 0.8 U PIVOT LINE DRAW A STRAIGHT
LINE TO 0.1 GUTTER SLOPE: 2.0" 0.6 READ Q: 9.0 c.I.•• FOR LOW CURB 0.5 0.4 MIN. CAPACITY OF PARABOLIC GUTTERS (40'& 44' STREET WIDTHS) FIGURE 4 
40! CAPACITY OF ALLEY SECTIONS n:0.0175 FIGURE 5 10' U.S'10' 'I I, U.s' 'I " 20' ALLEY 2S'ALLEY E.,...􀀮􀁦􀁾􀀠 16'ALLEY I' 6' I 6', I 6" 􀁾.. 12' LLEY 􀀢􀀠6" " " ." 􀁾 10'ALLEYI' 12.5'
'I" 12.5' I ·-'·lI ,". ,'.' 􀁾􀀠." ,.' ..... 2S'ALLEY I-10" .. 􀀶􀀺􀁾􀀧􀀠'I 􀁾􀀠􀀮􀁾􀀠20'ALLEY I' S' _I_ S' 'I 􀁾...􀁾􀀠16'A LEY /? //1000 900 800 700 600 500 400 300 200 100 90 80 70
60 SO 10 ! S EXAMPLE KNOWN: ALLEY WIDTH: 12' ALLEY DEPRESSION: 15" GUTTER SLOPE: 4.0" FIND: GUTTER FLOW (Ql SOLUTION: CONNECT THE 12' ALLEY SECTION WITH SLOPE: 4.0" READ Q: 14.9 c.!"'.
20.0 10.0 9.0 I-8.0 III III 7.0 1M 6.0.. S.O.. 4.0 3.0 2.0 1.0 0.9 0.8 0.7 0.6 O.S NOTE: 4 004 MIN. THE CAPACITIES OBTAINED FROM THIS NOMOGRAPH ARE BASED ONI' 􀁾􀀧􀀠'I5' 􀁾􀀠A STRAIGHT
HORIZONAL ALIGNMENT. CURVED ALIGNMENTS MAY RESULT IN REDUCED CAPACITY,􀁾􀁾􀁦􀁾􀀠10'ALLEY 81 
FIGURE 6 STORM DRAIN INLETS I AVAIL. DESIGNIINLET DESCRIPTION INLET WHERE USED CURVESI SIZESI I I I , ,􀁾􀀠 , -1---------______I--I : ST.... ND .... RD ClJRB OPENING : I INLET ON GR
.... DE I I I I 8' Residential Street, Collector 10' Street -Types C2UA and C2UB; Alley 12' 14 ' , I I 8' I Residential Street, Collector , 􀁾􀀠I I I -1_________ 􀁟􀁟􀁟􀁟􀁟􀁟􀀻􀁾􀀠I
10' I I ! Street -Types C2UA and C2UB; I ST....NO.... RD CURB OPENING I 12' I I Alley I INLET ....T LOW POINT I I 14' I I I I I I I 8' I Collector Street, Type C4U 􀁉􀁾􀀠I :., 􀁾􀀠􀀭􀁾􀁉􀀭􀀺􀀠10'
I I I Major Streets -Types M4U, M4D, I RECESSED CURB OPENING I I MSD, Principal Streets (PSD) I I I INLET ON GR.... DE I 12' I I I I 14' I I I I I I 􀀺􀁾􀁟􀁩􀀠 􀁉􀁾􀁉􀁾􀀠􀁾􀁉􀀭􀁉􀀠I
RECESSED CURB OPENING I I I INLET .... T LOW POINT I I I I I I I 8' I Collector Street, Type C4U I 10' I Major Streets -Types M4U, M4D, I I MSD, Principal Streets (PSD) 12' I I 14' I
I I FiguresI, 7 I I I Through I 11 I I I I I I I I Figure I 12I I I I I I Figures I 7 I I I Through I 11 I I I I I I I I Figure I I I I I 82 12 
_____ ________________ _ FIGURE 6 CONTINUED I AVAIL. I DESIGNI INLET DESCRI PTION INLET I WHERE USEDI 1 CURVESI ________________________ 􀁾􀁟􀁓􀁟􀁉􀁚􀁟􀁅􀁟􀁓__􀁾􀁉____________________________􀁾􀀭􀀭􀀭
􀀭􀀭􀀭1 I I I 1 Combination Inlets to be Used Figures 1 􀀬􀁾􀀮􀀠I 1 -[;;=::-: 􀁾􀀺􀀺􀀺􀀺􀀻􀀺􀀺􀁉􀁾􀀠1I ICOMBINATION INLH I ON GRADE 1 8' 1 II 1 Where Space Behind Curb Prohibits Other
Inlet Types 13 Through 15 1 I 1 1 I 1 1 1 1 I __ 1 1 Combination Inlets to be Used l--C;;Z:-:-S;:I-l I 8' Where Space Behind Curb Figure 1 COMBINATION INlET 1 I 16 Prohibits Other Inlet
Types1 AT LOW POINT I I 1 Must Be Approved By The I 1 I City Engineer 1______________________ 1 I I 2 GRATE , Grate Inlets to be Used Where Figures 1 1 171 􀁉􀁾􀁉􀁾􀁉􀀠3 GRATE I Space
Restrictions Prohibit THROUGH1 GRATE INlETS I I 4 GRATE I Other Inlet Types or At 20 1 Must Be Approved By The 1 1 City Engineer 6 GRATE 1 Locations with No Curb. I 1_________________
I I 1 2' X 2' 1 Open Channels Figure! I I} 􀁾􀁾􀀠i I: 3' X 3' 1 i 21 , DROP INLET 4' X 4' I I I1----____-----_____________________________ 83 
􀁦􀁩􀁴􀀺􀀮􀀧􀀭􀀧􀁌􀀧􀀺􀀻􀀧􀁾􀀺􀁈􀀺􀀧􀁕􀀠AI'll) .:;, !f\.I';Ur\i"'l) EXAMPLE KNOWN: PAVEMENT WIDTH: 30' GUTTER SLOPE: 2.0" S" PARABOLIC CROWN GUTTER FLOW: 5.2 c.I ••• FIND: LENGTH OF
INLET REQUIRED SOLUTION: ENTER GRAPH AT 5.2 c.I ••• INTERSECT SLOPE: 2.0" READ L!: 8.7' 2 CURB OPENING INLET CAPACITY CURVES ON GRADE DECISION: 1. USE 10' INLET NO FLOW REMAINS IN GUTTER
2. USE • 'INLET FIGURE 7 INTERCEPT ONLY PART OF FLOW USE 8' INLET ENTER GRAPH AT L I : 8' INTERSECT SLOPE: 2.0 " READ Q: 4.6 0.1... REMAINING GUTTER flOW: 5.2c.I••.-4.6c.f••• :.6 c.I••
4 5 6 7 8 9 10 15 20 25 30 50 40 30 20 15 10 9 8 7 50 30 20 15 10 9 8 6 ,... ,...--=--ill 􀀮􀁾􀀠STREET WIDTH CROWN 30: 36' F·F 􀁾􀁾􀀠PARA , , .. n: .0175 TYPE BOLIC • 􀁾􀀠It 􀁉􀀢􀁾􀀠•
.//' V /' ./V V V It' V /.: It' 􀁾/'V-I.-' /v.; M V 􀁾􀀠• 􀁾􀀠, II S_ a 4 􀁾􀁾􀀠􀁾􀀠-•3 ..2 1 2 3 4 5 6 7 • 9 10 15 25 30 QUANTITY OF FLOW IN C.F.S. 84 6 , .I 5 4 3 
RECESSED AND STANDARD CURB OPENING INLET FIGURE 8CAPACITY CURVES ON EXAMPLE KNOWN: GRADE DECISION: PAVEMENT WIDTH: 36' I. USE 10'lNLET GUTTER SLOPE: 3.0'" NO FLOW REMAINS IN GUTTER 112'lIt
CROSS SLOPE 2. USE 8' INLET GUTTER FLOW: 5.2 c.I... INTERCEPT ONLY PART OF FLOW FIND: USE S' INLET LENGTH OF INLET REQUIRED ENTER GRAPH AT LI:II' SOLUTION: INTERSECT SLOPE: 3.0," ENTER
GRAPH AT 5.2 <.f••• READ Q; 4.6 c.I... INTERSECT SLOPE: 3.0'" REMAINING GUTTER FLOW: 5Jlc.I.•.• 4..6<.I .•.:0.6c.l. 20 V ./V ./V ./l/"" 151... ./V l/vV V'" tm... I'.'" V. Z r;.-/.v ...
r."" Vv ALL 112 Inch CROSS SLOPE foot 􀁾􀀠10 !i 9... 0 8::... C) 􀁾􀁾􀀴􀀭􀁾􀀫􀀫􀀫􀀫􀁴􀁈􀀫􀁴􀁈􀀫􀁈􀀫􀁾􀁾􀁾􀁾􀁾􀁈􀁴􀁾􀁾􀀫􀀫􀀫􀀫􀀫􀀫􀁾􀁾􀁾􀀭􀁲􀁴􀁴􀁴􀁴􀀫􀀫􀁈􀁩􀁾􀁴􀁈􀀷􀀠... '" Z 6 ... 5
5 4 4 3 2.2. 1 2 3 4 5 6 1 8 9 10 15 20 25 30 QUANTITY OF FLOW IN C.F.S. 85 
RECESSED AND STANDARD CURB OPENING INLET FIOURE 9 CAPACITY CURVES EXAMPLE KNOWN: PAVEMENT WIDTH: 30' GUTTER SLOPE: 3.0110 PAVEMENT CROSS SLOPE: 1I4"/r GUTTER FLOW: 4.8 c.f.... FIND:
LENGTH OF INLET REQUIRED SOLUTION: ENTER GRAPH AT 4.8 c.f... INTERSECT SLOPE: 3.0 110 READ L I : 9,S' 1 2 50 I ON GRADE 4 􀀴􀀰􀁾􀀠30 􀁾􀀠􀀻􀀻􀀻􀀻􀀬􀁾􀀠,'<.;'''''' .. n: .0175 STREET
CROWN TYPE UWIDTH ALL 114 CROSS SLOPE 20 5 4 2 2 3 4 DECISION: 1. USE 10' INLET NO FLOW REMAINS IN GUTTER 2. USE S'INLET INTERCEPT ONLY PART OF FLOW USE 8' INLET ENTER GRAPH AT Lj: 8'
INTERSECT SLOPE: 3.0110 READ Q: 8,9 c.l.s. REMAINING GUTTER FLOW: 4.8 cJ.•:-S.9 c.I ••• :0.9 c.l. S6 7 8 9 10 15 20 25 30 40 􀁾􀀠30 20 5 4 2 5 6 7 8 9 10 15 20 25 30 QUANTITY OF FLOW
IN C.F.S. 86 1 
RECESSED AND STANDARD CURB OPENING INLET FIGURE 10CAPACITY CURVES EXAMPLE KNOWN: PAVEMENT WIDTH: 40' GUTTER SLOPE: 1.0" 6" PARABOLIC CROWN GUTTER FLOW, 6.5 c.i.a. FIND: LENGTH OF INLET
REQUIRED SOLUTION, ENTER GRAPH AT 6.5 c.l... INTERSECT SLOPE: 1.0 " REAO LI: 10" 1 :2 50 I<UU ,",V", Of-f-STREETr-CROWN TYPEI-􀁾􀁬􀁵􀁬􀁮.-3/8'"inchALL CROSS SLOPE 30 t= foot t= 40" F·F
6" PARABOL1C1= 1=1 44' F·F 6" PARABOL1C -, 20 15 II m 􀁾􀀠􀁾􀁶􀁾􀁶􀀠􀁾􀁲􀀯􀀠H 5 􀁾􀀠3 ON GRADE OECISION: 1. USE 10"INLET NO FLOW REMAINS IN GUTTER 2. USE 8" INLET INTERCEPT ONLY PART
OF FLOW USE a'lNLET ENTER GRAPH AT LI : 8' INTERSECT SLOPE: 1.0" READ Q: 5.0 c..r... RENAlNING GUTTER FLOW: 6.5 c..r... -5.0 cis :1.5 • 5 6 7 a 9 10 20 25 30 ,,' n: .0175 . I r/.//'
/' V ././r/./V '717 I/v/7. • 4 3 2 1 1 9 8 7 6 5 4 3t= 􀁾􀁾􀀠• 1 2 3 4 5 6 7 8 9 10 20 25 30 QUANTITY OF FLOW IN C.F.S. B7 
RECESSED AND STANDARD CURB OPENING INLET FIGURE 11CAPACITY CURVES EXAMPLE KNOWN: PAVEMENT WIDTH: 12' ALLEY SLOPE: 0.4:1; QUANTITY OF FLOW: 10.5e.I••• FIND: LENGTH OF INLET REQUIRED SOLUTION:
ENTER GRAPH AT 10.5e.I••• INTERSECT SLOPE: 0,4" READ L,: 13.0 It. 2 50 4 30 20 I 5 .... 5 4 ON GRADE DECISION: 1. USE 14' INLET NO FLOW REMAINS IN GUTTER 2. USE I O'INLET INTERCEPT ONLY
PART OF FLOW USE 10'iNLET ENTER GRAPH AT L I: 10' INTERSECT SLOPE: 0.'" READ Q: 7.3 oJ... REMAINING fLOWlNAU.EY: 10.5c.f•••-7.3eJ••• :3.2c.'" 1 8 9 10 15 20 25 305 6 15 20 25 30 88 150
f.ROU, " n: .0175􀁜􀁃􀁕􀀢􀁾􀁎􀁜􀁣􀁉􀁉􀀺􀀺􀀢􀀠014 ISTREET TYPEIWIDTH CROWN '" o r= ALL II" INVERTED 30 1= 2 o V 15V V r.;. :; V'[;' 􀁾􀀠l; I? l,.V 10 9 8 \.;' 1 1:. 611 5 4 II 3t=1=f.2
1 2 3 4 5 6 7 8 9 10 QUANTITY OF FLOW IN C.F.S. 
RECESSED AND STANDARD CURB OPENING INLET FIGURE 12 CAPACITY CURVES AT LOW POINT EXAMPLE KNOWN: SOLUTION: QUANITY OF FLOW: 19.0 c.I••• ENTER GRAPH AT 19 c.I••• MAXIMUM DEPTH OF FLOW DESIRED
INTERSECT yo: 0.5' IN GUTTER AT LOW POINT (yo):O.S· READ LI : 9.0' FIND: USE 10' INLET LENGTH OF INLET REQUIRED (LI) 2 3 4 5 6 7 8 9 10 15 20 30 40 50 60 708 5 2 0 10 ROUGHNESS COEFFICIENT
N:.0175 STREET 0 WIDTH CROWN TYPE ALL STRAIGHT AND PARABOLIC;. .-I II 'I II I I I I /V I if I wtztI II I II I I il if /1//I':' 􀁾􀀠ffi Y 2 3 4 III5 6 7 8 9 10 . 15 20 30 40 50 60 70
80 20 15 15 8 7 6 6 5 5 4 4 QUANTITY OF FLOW IN C.F.5, 89 
TWO GRATE COMBINATION INLET FIGURE 13CAPACITY CURVES ON GRADE EXAMPLE KNOWN, SOLUTION, ENTER GRAPH AT 9.0 c.I••• QUANITY OF FLOW, 9 c.1 ... INTERSECT SLOPE, 3.0 " GUTTER SLOPE, 􀀳􀀮􀀰􀁾􀀠READ
PERCENT OF FLOW INTERCEPTED: 61'; FIND: 61'; OF 9.0 c.I••• '5.5 c.I••• AS CAPACITY OF TWO GRATE CAPACITY OF TWO GRATE COMBINATION INLET COMBINATION INLET REMAINING GUTTER FLOW, 9.0 c.I••••
5.2 d .•• : 3.8 c.I••. vts: V V V 􀁾􀀠'( 􀁾􀁾􀀠1( • V V I..-V I,...L...l,...􀁾...... 􀁾􀀠V 􀁾􀀠::0..􀁾􀀠􀁾􀀠fc 1-' I..-Vi-,., J..j,...L.I--'1'\... 1..I--'vl\"", vJ,.)\...... I--'J..-v
v .... I--' V I-I..-v i,...􀁾􀀠􀁾V 􀁾V V V V.... 􀁾􀁩􀀭􀀭Vi-' ./i-􀁾l..-J..-i-l..rs. C 6J..i-'V . f\1--.... , l..-V 􀁉􀀮􀀮􀀭􀁦􀀩􀁾l..[\ V 􀁜􀀨􀁾􀀠1.;,'"" 􀁾􀀠,., I' 􀁾􀀻􀀠I-Ii 􀁾􀀬􀀠l..-J)
J.V I ! :I 4 5 6 7 8 9 10 15 20 , I 30 40 50 60 QUANTITY OF FLOW IN C.F.S. 90 
THREE GRATE COMBINATION INLET FIGURE 14CAPACITY CURVES ON GRADE EXAMPLE KNOWN' QUANTrTY OF FLOW, 15 e.I••• GUTTER SLOPE: 2.0 " FIND: CAPACITY OF THREE GRATE INLET SOLUTION: ENTER GRAPH
AT 15 c.f••• INTERSECT SLOPE: %.0 " READ PERCENT OF FLOW INTERCEPTED: 62" 62 "OF 15 .c.f•••: 9.3 e.f••• AS CAPACrTY OF THREE GRATE INLET REMAINING GUTTER FLOW, 15 e.f•••·9.3 e.f••• ,
5.7 c.f••• 􀁾􀀠􀁲􀀻􀁾􀁲􀀬􀀠􀁾􀀠i,..i,.....􀁾􀀠i-"i-'".> r., I'" ...'" i-'" >-..... '" 􀁾􀀠...... ...... ...... . < ......... ..... 􀁾􀁴􀀾􀀼􀀠'" ..... ..... '"c:'" '" i,..10V I< I--.
V ""::> 1>""'"V I--'V r<:; t:>-C L..l..V P f"r., I􀁾><V;k ....-'" ","'...'" ",i-' a '" ... ... " ... 􀁾􀁉􀀠􀁾􀀠􀁾􀀠V1.&' 􀁾􀀠I.-V->-V 􀁾􀁾􀀠f'; /t:-.-.􀁾􀁾􀀠/....􀁾􀀺􀀠􀁾􀁾􀀠􀁇􀁾􀀠􀁾􀀺􀁴􀀠􀁾􀀮􀀭􀀮􀀠t
,..0 􀁩􀀭􀀧􀁾􀀠i-' 0'" ... ... I"'" 15 20 30 40 50 602 3 4 5 6 7 g 9 10 QUANTITY OF FLOW IN C.F.s. 91 1 
FOUR GRATE COMBINATION INLET FIGURE 15 CAPACITY CURVES ON GRADE EXAMPLE KNOWN' QUANTITY Of FLOW: 12 c.I••• GUTTER SLOPE: 2.0 S FIND: CAPACITY OF FOOR GRATE COMBINATION INLET SOLUTION:
ENTER GRAPH AT 12 c.I••• INTERSECT SLOPE: 2.0 S READ PERCENT OF FLOW INTERCEPTED: 68 S 68 S OF 12 c.t•••: 1.2 c.I••. AS CAPACITY OF .. GRATE COMBINATION INLET REMAINING' GUTTER FLOW,
12 c.I•••·8.2 c.I••• : 3.8 c.I.8. 􀁾􀀠􀁾'> 􀁾􀁾􀀠􀁾􀀠􀁾•. >'>..t: ,.,. ,.,. 􀁾􀁾􀀠...... .... .... >,.,. ...... -... >< .... ........ ,.,.I'DI <. I.....,.,. .... 􀁉􀁾􀀠........ P'" ....
i.-' V i.-'k I->V i--" 1-01-"'> i.-' r'-I P? k:: ... "'" V i< ........ "" .... r"" ...r􀁾􀀠1-0 >.... .... 1-0 I-􀁾􀁾􀀮􀀠􀁾􀀠\1 11V I---' 􀁾􀁾,. ..-' I---' 􀁩􀁥􀁾􀀠􀁾􀀠V I---' ..-' "
􀁾􀁉􀀭􀁯􀁲􀀭I---' ,.,. .,.."'(' . ..., 􀁾􀀠,.,. ..-' "" ........ 􀁾􀀠􀁾,.,. 􀀮􀀭􀀺􀁾􀀠.... C' 􀁾􀀠,.,. .... (, 1 2 3 .. 5 6 7 8 9 10 15 20 30 40 50 60 QUANTITY OF FLOW IN C.F.S. 
COMBINATION INLET CAPACITY CURVES AT LOW POINT FIGURE 16 EXAMPLE KNOWN: SOLUTION: QUANTITY OF FLOW: 20.0 c.I.•• ENlER GRAPH AT 20.0 c.f••• MAXIMUM DEPTH OF FLOW DESIRED INTERSECT 􀁾􀁯􀀠:
0.5' AT,LOW POINT (yo) : 0.5' READ LI : 8.4 FIND: USEIO'INLET LENGTH Of INLET REQUIRED ILl) 25 2 3 4 5 6 1 8 9 10 nllllll III I 1 o o 40 50 I 20 5 4 1l1l1lUi i.L.. I JJ.IIIIII ..1. ROUGHNESS
COEFFICIENT." .0115 CROWN TYPE I II V 􀁾􀀴􀀫􀀫􀁈􀁾􀀫􀁈􀁾􀀯􀁾􀀭􀀪􀀭􀀫􀁁􀀭􀁾􀁩􀁪􀀴􀀴􀁾􀁾􀀲􀀰j 1/STREET WIDTH ALL STRAIGHT AND PARABOLIC lHH-l+ll++lcH-lKMt---lV(.......J1-c1/i+-1H/-t-J1-I---H
I I //il l""l 1/7 :j 4 5 6 7 8 9 10 15 20 SO 40 50 60 70 802 4 Q-QUANTITY OF FLOW IN C.F.S." 93 
TWO GRATE INLET CAPACITY FIGURE 17CURVES ON GRADE EXAMPLE KNOWN' SOLUTION, QUANTITY OF FLOW, 5.0 d .•. ENTER GRAPH AT 5.0 c.I.•. GUTTER SLOPE, 0.6" INTERSECT SLOPE: 0.6 " FIND, READ
PERCENT OF FLOW CAPACITY OF TWO GRATE INLET INTERCEPTED: 63" 63 "OF 5.0 c.I••• : 3.2 c.I••• AS CAPACITY OF TWO GRATE INLET REMAINING GUTTER FLOW, 5.0 c.I... '3.2 c.t.•• , 1.8 c.I•••
􀁾􀀠1\.01 L--􀁾􀀠('\t'> V 􀁾....... 10' 􀁾􀀠" V ,,'􀁾􀁾􀁲􀁾􀀠!IoV 􀁾.1 􀁾􀁾􀀠..... 􀀡􀀭􀀭􀁾I'! ,..........􀁾􀀠.... .....􀁾􀀠...... 􀁾.... ""\ ..... ....... K !-,....... ..... ......
􀁾􀁌􀀮......V 1\ ....􀁾􀀠I....􀁾􀁶􀀢􀀢􀁋􀁾􀀠􀁾􀀠. ts:v V v 􀁾􀀠􀁾􀀠􀁶􀀢􀀢􀁾􀀱􀁜􀀠􀁾􀀠􀁾􀀠...... 􀁾􀀢􀀬􀀬􀀡􀀭􀀭􀁉􀀭􀀧v.........V 􀁾􀀠􀁾􀁾􀀠.........-v 􀁾􀀠 .........􀁾􀀠• i , .... l 􀁾􀀠....
fl< ')..... ..... \ ...... 􀁾􀀺..... 􀁾􀀢􀀢􀀠, 􀁾􀁾􀀠...... ............. ............... 􀁾􀀠􀁾).......... ...... ..... l..1\ I1 3 4 5 iii 7 8 9 10 15 20 30 40 50 60 QUANTITY OF FLOW
IN C.F.S. 94 
FOUR GRATE INLET CAPACITY CURVES ON GRADE FIGURE 18 EXAMPLE KNOWN: QUANTITY OF FLOW, 20 c.f••. GUTTER SLOPE: 1.0 􀁾􀀠FINO: CAPACITY OF FOUR GRATE INLET SOLUTION, ENTER GRAPH AT 20 c.I
.•• INTERSECT SLOPE: 1.0 􀁾􀀠 READ PERCENT OF FLOW INTERCEPTED: 63 iii 611 iii OF 20 c.I•••: 12.6 c.I .•• AS CAPACITY OF FOUR GRATE INLET REMAINING GUTTER FLOW: 20.0 c.f••• -12.6 c.f•••
= 7.4 c.r••• II< :;; II<􀁾􀁾􀀠H II>'" '" V .....􀁩􀁾􀀠fu 6 V VI-' V 1I <:'>!:, ""􀀱􀁾􀁾􀀠V :...-2􀁾􀁾􀁬􀀭V Ii: ..... I-' V V 􀁾...... 􀁾􀀠i-' 􀁾􀀠..... 􀁉􀀮􀀮􀀮􀀭􀀭􀁬􀁾􀀠􀁾!! :,... I-'i-'
􀁾􀀠􀁾􀀠1;:"'-􀁾􀀠􀁾􀀠G 􀁾􀁔􀀠􀁾􀁅iI'''' """"""f' S ,-0 Ek ........... 􀁾􀀠f'l-' ...... I-'f' V V I......... .}􀁾􀀠""f'""f'"" ........... V I................ 􀁾􀀠 v 􀁾􀀠........... ..........
................. -V ;:;V v ............ 0'1 .......... v V.t ...... I ............ .......... ....... ............ .......... 􀁾􀀠 V -1 ..........." ...... 1 1 2 3 4 5 6 7 8 9 10 15
20 30 40 50 60 QUANTITY OF FLOW IN C.F.S. 95 
SIX GRATE INLET CAPACITY FIGURE 19CURVES ON GRADE EXAMPLE KNOWN; QUANTITY OF FLOW. 4.0 c.I••• GUTTER SLOPE: 3.0" FIND: CAPACITY OF SIX GRATE INLET SOLUTION. ENTER GRAPH AT 4.0 .:.f ••.
INTERSECT SLOPE: 3.0" READ PERCENT OF FLOW INTERCEPTED. U" 85"OF 4.0 <:.f..... 3.4 c.f••• AS CAPACITY OF SIX GRATE INLET REMAINING GUTTER FLOW. 4.0 c.I... • 3.4 c.f••• : 0.6 c.f••• 1
􀁾􀀠􀁾􀀠1 􀁾􀀠􀁉􀁾􀁾􀀢􀁬,"ii I .... 't/#􀁾....... /lIU ....... 􀁾􀀠􀁾􀀠""" ....... /) ...., v 􀁾v vi.; ..... 􀁾􀀠.... 􀁾􀀠i.-i.-􀁾􀀠􀁾􀀠K: l,.; v -􀁾􀁲􀀬􀀠..... ......􀁾􀁉􀁜􀀠I--􀁾􀁉􀀭􀀧􀀠""......
i-" ...i-" "" '" i-"i-" ",,'" ",,'" "".... 􀁾􀀠'" 􀁾􀀠􀁾􀀨􀀠'10 rtJ 􀁖􀁾􀀠f.&,V V i-" /l,' vi-"..s i-" -"" V 􀁾􀁾􀁾􀀺􀀠􀀧􀀭􀀢􀁾􀀠􀁾􀀧􀀢􀀢􀁾􀀠􀀭􀀭􀀢􀀢􀁾􀀠Is . ... 1-I-",'" ",'" ... 5
6 7 8 11 10 15 20 30 40 50 60 QUANTITY OF FLOW IN C.F.S. 96 :2 3 4 1 
.. Uol Uol ... Z-i!J 0 􀁾􀀠... ... 0 :c..... 11.1 Q 2 0.7 i 0.6 i 0.5 0.4 0.3 0.2 , 1.1 GRATE INLET CAPACITY CURVES AT LOW POINT EXAMPLE KNOWN: SOLUTION: QUANTITY OF FLOW: 4.8 c./.••
ENTER GRAPH AT 4.8 MAXIMUM DEPTH Of FLOW DESIRED INTERSECT 3 • GRATE AT LOW POINT: 0.4' INTERSECT 2 • GRATE FIND: USE 3 • GRATE INLET REQUIRED :I 4 5 Ii 7 8 9 10 I.-----r ----//1/I I
V I I te!, . 􀁾􀀠I r/I I I '( I /II I II , I /I II //, /II /:I 4 5 6 7 8 9 10 QUANTITY OF FLOW IN C.F.S. 97 0.7 J 0.6 0.5 0.4 0.3 0.2 : I 0.1 15 FIGURE 20 c.I••• AT (1.28' AT G.63' 15

DROP INLET CAPACITY CURVES AT LOW POINT FIGURE 21 EXAMPLE . KNOWN: SOLUTION: QUANTITY OF FLOW: 12 c.! ••• ENTER GRAPH AT 12 c.!.•. MAXIMUM DEPTH OF FLOW INTERSECT yo: O.S' DESIRED (yol:
0.5' READ L I : 12.3 FIND: USE 12.3 OF INLET 4x4 LENGTH OF INLET OPENING REQUIRED (LI) 1 s 4 5 6 7 8 910 15 20 30 U rrl I "rt 1/'Y II 1/. //'. II I. 􀁾􀀠.j I II .r f 1/-f . ----r---I
yt /II V I; 􀁾􀀠1I II I j II /I V I I /II I I II j II /V I I f /f II II imI I /f III 2020 4,,4IIII 1515III ... ;z:-I:) ;z: :lx3-;z: III ... 0 10I-10 III ... ;z: 9-• ... 0 8 2><28 = l-I:)
;z: 7 7 III ... 6 55 44 1 2 :I 4 5 6 7 8 910 15 20 30 40 QUANTITY OF FLOW IN C.F.S. STANDARD DROP INLET SIZES: 2'x 2" Li:S' 3'x 3', LI:12' 4'x. 4', LI:16' 98 
•• .. .. .. .. ..t_,... .. Oi ... ."".00 .oo 700 700 600 600 5005"" .00 400 300 300 200 200 􀁾􀀠􀁾􀀠􀁾100 10. u. 9090 " 80 80 " 70 60 5. •0 3. 20 10 9 8 7' 60 SO 3. 20 ••10 􀁾􀀠a 􀁾􀀠0
a " u 􀁾􀀠􀁾􀀠􀁾􀀠'" 􀁾􀀠􀁾􀀠􀁾􀀠UJ '" :: ::; '" u 􀁾􀀠3 0 ... u. 7 7 6 6 S 4 • 3 3 2 2 SLOPE. OF piPE IN FEET PER 100 FEET CAPACITY OF CIRCULAR PIPES FLOWING FULL FIGURE 22 A GRAPHICAL
SOLUTION OF MANNING'S EQUATION V '. 1.486-n-nn 213 S112 n : 0.013 99 
OUTFALL OF A STORM SEWER INTO A CHANNEL FIGURE 23 DESIGN TAILWATER ... NORMAL TAILWATER (NOT ALLOWED) DESIGN TAILWATER 20' OR GREATER FOR 90· INTERSECTION ANGLE NORMAL TAllWATER RIPRAP
PROTECTION MIN.:IO·x DIA. (ALLOWED) • OUTFALL SLOPE SUCH THAT NONEROSIVE EXIT VELOCITIES WILL OCCUR. 100 
FIGURE 24 Approximate Routing Method for Watersheds < 160 Acres E(!) a:: « J: () (1) Cl I To + Tep Qp (1) u.. STORAGE VOLUME (V.l w Q() 􀀱􀁉􀀺􀀢􀁲􀀬􀀮􀀬􀀮􀀮􀀬􀀮􀀮􀀬􀀮􀀮􀀬􀀭􀀮􀀮􀀮􀀮􀀬􀀮􀀮􀀮􀀮􀀮􀁾􀀢􀀧�
�􀀢􀀢􀀧􀀮􀀬􀀮􀀮􀀬􀀬􀀢􀀢􀀢􀀢􀀭􀀭Q 0 = Q E TIME (MINUTES) y,,( 60) [(QD[(TD -TCp)+(TD+TCp)]12) -(QE[TCp+TD]I2)] in cubic feet. Or y" 60 (<4lt2) (TD -TCp) Where: Qp = Peak discharge in
cfs for developed watershed using storm duration equal to TCp. Qe = Peak discharge in cfs for existing watershed, assuming full residential development and corresponding TC . QD = Peak
discharge in efs for developed watershed, based on a storm duration that yields the existing discharge for Cp and A. TCp = Time of concentration in minutes for proposed development.
TD = Storm duration in minutes corresponding to ID' In = Rainfall intensity (incheslhour) for a storm duration that produces QD and is calculated using the following formula: QD ID=
(CpA) Cf Where: Cp = Rational "c" for developed condition. A = Drainage area in acres. Cf = Frequency factor coefficient of 1.25 101 
FIGURE 24, continued Detention Basi n Example: Development Oata: Orainage Area = 160 acres Residential C '" 0.55 Residential T CR '" 15 minutes Developed Cp = 0.70 Oeveloped TCp = 10
minutes Cf '" 1.25 Forthe 100"year storm: IRES = 7.52 inJhour (from Figure 1) Ip = 8.82 inJhour. QE Qo'" (1.25) (0.55) (7.52) (160) = 827 cfs '" Qp (1.25) (0.70) (8.82) (160) '" 1235
cfs '" Qo 827 10 = = 5.91 inJhour'" (Cp A) Cf (.7)(160)(1.25) From Figure 1, for 10 = 5.91 inlhour. TO = 28 minutes v = = 24,810 (18) =446,580 cubicfeet 102 
" -----􀁾􀀧􀀬􀀠-------------------1""'-+-v ' I , t" I /" FLOW I 􀁾􀀫􀁾􀀠" II 􀁾􀀠" /􀁾􀀠 􀁾􀀠, I Q , 􀁟􀀮􀀭􀀭􀀭􀀭􀁾􀀭􀀢􀀢􀀧􀁜􀀮􀀠J;r---II I II I IT t fI t -r..... :", 􀁾􀁒􀁟􀁉􀁟􀁄􀁟􀁇􀀢􀀽􀁅􀀽􀁾􀁾􀁾􀀭
􀀯􀁀􀁾􀁾􀁾􀁾􀁾􀁖􀁾􀁉􀁾􀁉􀁾􀁉􀁾􀁉􀁾􀁬􀁾􀁉􀁛􀀭II I II II I I II ".............. CONSTR I cnON \ 11 1 1 1 1 11 .. I I I II ------./1 \ '------I \ I \ 1 \ I NEFFECTI VEI \I \ FLOW AREA1
􀁾􀀠I \ \ (;; /\ \i /""\. "NATURAL FLOODWAY" FLOODPLAIN\::.( 1 o I (EFFECTIVE FLOW 􀁁􀁐􀀮􀁅􀁁􀁾􀀠.... I os LIMITS). I ,.. I \ \I \I \I \I FLOW 􀀨􀁾􀀠\1 I \ 1 \ 1 \ 1 \ -----r-'--------------------.-:
...'+----FIGURE 25. "NATURAL FLOODWAY" EXAMPLE 103