OR 87-390 Provides for comprehensive management of floorplains in the City
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CITY OF COPPELL
FLOODPLAIN
ORDINANCE
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ORDINANCE NO. 87390
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ORDINANCE NO. 87390
AN ORDINANCE OF THE CITY OF COPPELL, TEXAS, PROVIDING FOR COMPREHENSIVE
MANAGEMENT OF FLOODPLAINS IN THE CITY OF COPPELL:
PROVIDI1NG A TITLE; SHOWING STATUTORY AUTHORITY: LISTING FINDINGS OF FACT;
STATING PURPOSES AND METHODS; DEFINING SCOPE OF AUTHORITY; OUTLINING THE
ORGANIZATION OF THIS ORDINANCE; PROVIDING DEFINITIONS OF TERMS: DEFINING
LANDS TO WHICH THE ORDINANCE APPLIES; IDENTIFYING AREAS AND METHODS OF
DETERMINING SPECIAL FLOOD HAZARDS; ESTABLISHING A PENALTY OF FINE FOR
NONCOMPLIANCE; DEFINING PREVAILING RESTRICTIONS; MAKING INTERPRETATION
PROVISIONS; PROVIDING WARNINGS AND DISCLAIMERS OF LIABILITY; ESTABLISHING
ADMINISTRATIVE AND VARIANCE PROCEDURES, INCLUDING PERMITS, DESIGNATION OF
CITY ENGINEER AS ADMINISTRATOR, AND DEFINING DUTIES AND RESPONSIBILITIES OF
THE ADMINISTRATOR; MAKING GENERAL AND SPECIFIC DESIGN AND PERPORMANCE
PROVISIONS FOR METHODS OF REDUCING LOSSES; AND DECLARING AN EFFECTIVE DATE.
NOW THEREFORE, BE IT ORDMNED BY THE CITY COUNCIL OF THE CiTY OF COPPELL,
TEXAS:
ARTICLE 1
Adoption and Title, Statutory Authority, Findings of Fact, Purposes and
Methods, Scope of Authority, and Or~niTation
SECTION A. Adoption and Title
This Ordinance is hereby adopted and shall be known as the "Floodpiain
Management Ordinance" of the City of C~ppell.
SECTION B. Statutory Authority
The Legislature of the State of Texas has in Articles 1175 and Water Code
Section 16.311 et~seq. delegated the responsibility to local governmental
units to promote the public health, safety and general welfare of its
citizenry for protection against the perils of flood losses and to
encourage practices mhtimizing exposure to flood losses. Therefore, the
City Council of the City of Coppell, Texas has enacted this ordinance to
establish such regulations.
SECTION C. Fincl~ngs of Fact
1. The riverine areas of the City are subject to periodic inundation which
may result in loss of life and property, health and safety hazards,
disruption of commerce and governmental services, extraordinary public
expenditures for ~cxxi protection and relief, and impairment of the tax
base, all of which adversely affect the public health, safety and
general welfare of its citizenry.
2. Among the causes of these flood losses are the cumulative effects of:
a. Obstructions in areas of special flood hazards which increase flood
heights and velocities, and when improperly placed, damage uses in
b. Uses that are inadequately floodproofed, elevated or otherwise
protected from flood damage;
c. Quick intense overflows of water resulting from combinations of
steep slopes, short drainage basins, and high proportions of
surfaces impervious to water and ~m~ble to absorb runoff;
d. Modifications to drainage patterns and displacement of natural
vegetation with nonporous surfaces for buildings, roads, and
parking; and
e. Lack of comprehensive basin-wide planning to manage the rive fine
floodplains in order to reduce the losses incurred when the
inevitable floodins takes place.
3. The riverme areas of the City are a valuable resource to the citizenry
Lq that they provide focal points for development, recreational
opporl~mities, and aesthetic enjoyment potential.
4. As valuable resources and as flood hazard areas, the rive fine systems
of the City should be managed for the welfare of the citizenry.
SECTION D. Purposes and Methods
It is the purpose of th/s ordinance to promote the public health, safety
and general welfare, and to minimize public and private losses due to flood
conditions in specific areas by managing the floodplains of the City.
Further, it is the purpose of this ordinance to establish the various
public and private responsibilities for management of the floodplains with
provisions designed to:
1. Protect human life, health, and property;
2. Minimhe expenditure of moneys for costly flood control projects;
3. Min/mize the need for rescue and relief efforts associated with
flooding and frequently undertaken at the expense of the general
public;
4. Minimize prolonged business interruptions;
5. M~n~mize damage to public facilities and utilities such as water and
gas mains, electric. telephone and sewer lines, streets and bridges;
6. Help maintain a stable tax base by providing for secondarJ uses and
development of floodplain areas (the primary use being conveyance of
floodwaters);
7. Ensure that potential buyers are notified that properr/ is in an area
of special flood hazard;
8. Ensure that those who occupy the areas of special flood h~7~rd assume
responsibility for their actions;
9. Restrict or prohibit uses which are dangerous to health, safety, and
propert~ due to water or erosion hazards, or which result in damaging
increases in erosion or in flood heights or velocities;
10. Require that uses vulnerable to floods, including facilit/es which
serve such uses. be protected against flood damage at the time of
initial construction;
11. Control the alteration of natural floodplains, stream channels and
natural protective barriers, which help accommodate or channel flood
waters;
12. Control, filling, grading, dredging or other development which may
increase flood damage; and
13. Prevent or regulate the construction of flood barriers which will
unnaturally diver~ flood waters or which may increase flood hazards in
other areas.
SECTION E. Scope of Authority
Except as exempted by Article 3, Section A, any person, firm, corporation,
business, or public agency proposing to develop land or improve properly
within the City is subject to the provisions of this ordinance. This
ordinance also applies to individual building structures, subdivisions,
excavations, fill operations, and similar activities.
SECTION F. Org~niT~tion of this Ordinance
This ordln~nce is organized into five articles as follows:
Article 1 - States the adoption, title, authority, findings, scope and
organization of the ordinance.
Article 2 - Lists and defines various terms used in the ordinance.
Article 3 - States the general provisions, bases, and penalties of the
ordinance for interpretation, implementation and enforcement.
Article 4 - Outlines administrative procedures for the conduct and
maintenance of a permit program to msn~ge and regulate the
development along and within floixtplains.
Article 5- Outlines minimum design and performance standards and criteria
required for the management of floodplains and special flood
hazard areas.
Article 6 - Establishes the effective date.
SECTION G. Related Ordinances
In addition to this ordinance, the Cit)' of Coppoll has other ordinances,
regulations, and standards and specifications directly or indirectly
pertaining to drainage and storm sewer facilities and design requirements.
Ordinances include the City of CoppeI1 Zo~ng Ordinance. City of Coppeli
Subdivision Ordinance; planning documents include the City of CoppeI!
Streetscape PIth, City of CoppelI Partc and Recreation Plan, and the City of
Coppell Comprehensive PIth. and related standards among others.
Developers, builders, engineers, or others involved with new construction
or development of lands in the City of Coppoll should refer to these
documents and to the Code of Ordinances of the City of CoppelI. Texas for
additional requirements and infomation concerning stormwater drainage
facilities.
ARTICLE 2
Definitions
Unless specifically defined below, words or phrases used in this ordinance
shall be interpreted so as to give them the meamng they have in common
usage for floodplain management purposes to give this ordinance its most
reasonable application.
"Ad.~m'nistratoc" See "Floodplain Administrator."
"Appeal" A request for a review of the interpretation of any provision of
this ordinance or a request for a variance.
"Appeal/~oard" The Coppell City Council or a specific board appointed by
the Council to hear and decide appeals and requests for variances from the
requirements of this ordinance.
"Appurtenant structure" A structure wkich is on the same parcel of
property as the principal structure and the use of which is incidental to
the use of the principal structure.
"Area of shalIow flooding" A designated AO, AH or VO Zone on the Flcxxi
Insurance Rate Map (FIRM) with a one percent or greater annual chance of
flooding to an average depth of one to three feet where a clearly defined
channel does not exist, where the path of flooding is unpredictable and
where velocity flow may be evident. Such flooding is characterized by
pending or sheet flow.
"Area of special flood hazard" The land in the floodplain within the City
subject to a one percent or greater chance of flooding in any given year.
The area may be designated as Zone A, AO, AH, Ai-99, or AE.
"Backwater" The rise in water surface elevation caused by some natural or
manmade obstruction such as vegetation, narrow openings, bridges,
buildings, or fill materials which limit the area through which the water
flows.
"Base flood" The flood having a one percent chance of being equaled or
exceeded in any given year. It should be noted that the magnitude of the
"base flood" is subject to change as the watershed conditions change; thus,
the term ''base flood" as used in this ordinance may mean either of two
floods: (1) the base flood of the effective FIS or, (2) the design base
flood. See "Design base flood."
"Base flood elevation" (BFE) The elevation for which there is a one
percent chance of being equaled or exceeded.
"Basin" The total area from which surface runoff is carried away by a
drainage system. Comparable terms in common usage include "drainage area,"
"catchrnent area," and "watershed." "Basin" generally refers to a larger
system; e.g. the City of Coppell is in the Trinity River Basin.
"Basement" Any area of a building having its lowest floor below ground
level on all sides.
"Breakaway wal1"A wall that is not part of the structural support of the
building and is intended through its design and construction to collapse
under specific lateral loading forces, without causing damage to the
elevated portion of the building or supporting foundation system.
"Building" See "Structure."
"clrs'' Cubic feet per second; a unit of discharge used to describe the
volume of flow passing a given point in a stream channel.
"Critical depth" The condition of minimum specific energy corresponding to
the critical state of flow. At the critical state, two alternate depths of
flow possible at a given specific energy are in transition and apparently
become one.
"Cn'tical feature" An integral and readily identifiable part of a fiveme,
lacustrine, or flood protection system, without which the natural or
intended operation provided by the entire system would be cornpromised.
"Cross section" A graph or plot of ground elevation across a stream valley
or a portion of it, usually along a line perpendicular to the stream or
direction of flow.
October 8, 1987 - ?ag~ ?
"csm" Cubic feet per second per square mile of watershed area.
"Design discharge" A hypothetical discharge determined, in the case of
this ordinance, by scientific study of a fully urban~zed watershed to
establish a flood which may include, but is not necessarily limited to, low
flows, base floods, full development (design) base floods, probable maximum
floods, standard project floods, or any statistically based mean recurrence
interval flood used to meet acceptable design standards for a riverine or
lacustrine system. See "Design base flood."
"Design base Hood" The one-h~mdred year mean recurrence interval (lO0-
year) flocd which will result during the design discharge from runoff from
a fully urbanized watershed. For design purposes in this ordinance, it can
be assumed that a lO0-year precipitation event will produce a lO0-year
rimoff event.
"Development" Any maD. made change to improved or tinimproved real estate,
including but not limited to buildings or other structures, mining,
dredging, filling, grading, paving, excavation or drilling operations
located within the floodplain management areas of the City. See
"Floodplain development permit."
"Development perttilt" See "Floodplain development permit."
"EIevated building" A building located in SFHA Zones AI-99, AE, A. AO, AH,
B, C, X. or D, with the lowest floor elevated above the ground level and
above the design base flood by means of pilings, columns (posts and piers),
or shear walls parallel to the flow of the water and adequately anchored so
as not to impair structural integrity of the building during a flood of up
to the magnitude of the design base flood and further includes a building
elevated by means of fill or solid foundation perimeter walls with openings
sufficient tO facilitate the tinimpeded movement of flood waters.
"Encroachment" Any activity in a floodplain which hinders the passage of
water or otherwise affects flood flows; e.g. fill, buildings, fences, and
so om
"Enclosure" An area subject to flooding which is constructed based upon
flood resistant design concepts to create a structure at or above adjacent
grade solely for parking of vehicles, essential temporary storage, building
access or other real or perceived need which is otherwise impossible to
construct outside of flood elevations provided that such enclosure is not
built so as to render the structure in violation of the applicable non-
elevation design requirements of this ordinance.
"Erosive velocity" That average velocity of moving flood waters wMch will
begin to cause erosion of the parent materials of the channels, overbanks,
or areas of shallow flooding. See "Maximum permissible velocity."
"Equal conveyance aIteration" The principle of changing the conveyance at a
stream cross section by altering the conveyance lost in each overbank of
the section an equal amount. Conveyance is defined in units of cfs as a
function of the roughness and the flow area and hydraulic radius at the
cross section.
"Existin~ conditions" The floodplato conditions established by a flood
elevation study based on land use as of the date of the study completion.
"Existin~ construction" Structures for which the "start of construction"
commenced before August 1, 1980. "Existing construction" may also be
referred to as "existing structures."
~Existin~ structures" See "Exisdn~ construction."
"Federal Emergency Management A~ency" (FEMA) The Federal agency which
administers the National Flood Insurance Program.
"Flood" or "flooding" A general a~d temporary condition of partial or
complete inundation of normally dry land areas from water from any source
causing:
I. The overflow of waters normally contained within stream banks, open or
closed ch~n~els, lakes, ponds, tanks or other storage areas and/or;
2. The unusual and rapid accumulation or runoff of surface waters.
"Flood eievation determination" A determination by the Administrator of
the water surface elevations of the base flood, that is, the flood level
having a one percent or greater chance of occurrence in any given year
under exisfin~ or design conditions.
"Flood elevation study" An examination, evaluation and determination of
flood hazards and, if appropriate, corresponding water surface elevations
and/or flood-related erosion hazards under existing or design conditions.
"Flood fringe" or "floodway fringe" The portion of the floodplain
outside of the reg~latory floodway but still subject to flooding.
"Flood Hazard Boundary Map" (FHBM) An official map of the flood areas
delineating the boundaries of the flood and related erosion areas having
special hazards designated as Zones A, M, and/or E.
"Flood Insurance Rate Map" (FIRM) The official map on whjch the Federal
Insurance Administration has delineated both the areas of special flood
hazards and the risk premium zones applicable to the Ci~.
"Flood fnsurance Study" (FIS) The official report of a flood elevation
study in which the Federal Insurance Administration and the Federal
Emergency Management Agency have provided flood discharges, elevations,
profiles, maps, and related flood hazard information of existing conditions
in the City.
"Floodplain." "floodplato land" or "flood-prone area" Any normally
land area susceptible to being inundated by water from any source (see
"flooding") and referenced to some statistical mean recurrence interval,
most frequently the 100-year mean recurrence interval floodplain.
"Floodplain Adrra'nistrato~' The City Engineer of the City of Coppell as the
admimstrator of the provisions of this ordinance.
"Floodplain Developrnent Permit" A permit which must be obtained by any
person before any development begins on land within a floodplain. See
"Development."
"Floodplain management" The operation of an overall program of corrective
and preventive measures for reducing flood damage, including but not
Limited to emergency preparedness plans, flood control works and floodplain
management regulations.
"Floodplain management area" All floodplain lands within the jurisdiction
of the City whether or not the land is within an identified special flood
hazards area.
"Floodplain management regulations" The zoning ordinances, subdivision
regulations, building codes, health regulations, special purpose ordinances
(such as this floodplain ordinance), and other applications of police
power. The term describes such City, County, State, or Federal
regulations, in any combination thereof, which provide standards for the
purpose of flood damage prevention and reduction.
"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 area within the City subject to a "special flood hazard" and the
extent of the depths of associated flooding. Such a system typically
includes channel improvements, reservoirs, levees or other specialized
flood modifying works constructed in conformance with sound engineering
standards.
'Floodproofing" Any combination of structural and non-structural additions,
c]~nges, or adjustments to structures which reduce or eliminate flood
damage to real estate or improved real property, water and sanitary
facilities, structures and their contents.
"Flood-related erosion" The collapse or subsidence of land along the
fiveme flow line, or banks, the shore of a lake or other body of water as
a result of undermining caused by waves or currents of water exceeding
normal and anticipated levels or suddenly caused by an unusually high water
level in a riverine or lacustrine environment accompanied by a severe
storm, or by an unanticipated force of nature, such as a flash flood or an
abnormal surge of water from some similarly unusual or unforeseeable event
which results in flooding.
"Flood-related erosion area management" The operation of an overall
program of corrective and preventive measures for reducing flood-related
erosion damage, including but not limited to emergency preparedness plans,
flood-related erosion control works, and flo<xiplain management regulations.
"Floodway" See "Regulatory floodway,"
"Floodway encroachment lines" The lines marking the limits of the
regulatory floodways on Federal, State and City floodplain maps.
"44 CFR" The National Flood Insurance Program Regulations, Chapter 1,
Subchapter B, of 44 Code of Federal Regulations. Copies are available from
the Texas Water Commission or the Federal Emergency Management Agency.
"Freeboard" A factor of safety usually expressed in feet above a flood
level for purposes of floodplain management. "Freeboard" tends to
compensate for the many unknown factors that could contribute to flood
heights greater th~n the height calculated for a selected size flood and
floodway conditions, such as wave action at bridge openings, and the
hydrological effect of urbanization of the watershed.
~Functionally dependent use" A use which ca.lmot perform its intended
purpose unless it is located within or in close proximity to water.
"Highest adjacent grade" The highest natural elevation of the ground
surface at a given location prior to any development on the site.
~[ndependent scientific body" A non-federal technical or scientific
organization involved in the study of land use planning, flOodpJ~n
management, hydrology, geology, geography, or any other related field of
study concerned with flooding.
"Lacustrine" Of or perta~ninE to natural or manmade lakes, ponds, or
reservoirs.
"Land use zoning" The ordinance or master plan of the City which divides
an area into districts and, within each district, regulates the use or
desired planning for use of land and buildings including the height and
bulk of buildings or other structures, and the density of population and
general purposes of the buildings.
"Levee" A man-made structure, usually an earthen embankment, designed and
constructed in accordance with sound engineering practices to contain,
control, or divert the flow of water so as to provide protection from
temporary flooding.
"Levee System" 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.
"Low-Flow" The scientifically determined or assumed discharge to occur in
a riverine system during periods of dry weather. May be, but is not
necessarily limited to, the stream base-flow, water table discharge, or,
for design discharge purposes of this ordinance, assumed as not less than
5-cfs per square mile (5-csm) of watershed.
"Lowest Floor" The lowest floor of the lowest enclosed area of a building
(including basement). An unfinished or flood resistant enclosure, usable
solely for parking of vehicles or build~n~ access, in an area other than a
basement, 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 of this ordinance.
"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 floodplain 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. For insurance purposes
the term "manufactured home" does not include park trailers, travel
trailers, and other similar vehicles.
"Mar~factured Home Park or Subdivision" A parcel (or continuous parcels)
of land divided into two or more manufactured home lots for rent or sale.
"Map" The Flood Hazard Boundary Map (FHBM), the Flood Insurance Rate Map
(FII~M) or other official floodplato map of the City approved by the
Admimstrator or issued by the Federal Emergency Management Agency.
"Maximum perrrdssible velocity" The greatest average velocity which will be'
allowed for design of channels. These velocities are variable dependent on
depth, parent materials, sinuosity, and silt load (among other factors).
For purposes of this ordinance, design of channels, overbanks, and shallow
flooding areas shai1 be based on the maximum permissible velocities of the
City of CoppeIi Subdivision Ordfnance.
"Mean annual fIood" Generally defined as the the flood having a mean
recurrence interval of approx/mately 2.33-years; defined for purposes of
this ordinamce as the discharge having a ,50% probability of bem~ equaled
or exceeded in a given year (the 2-year mean recurrence interval).
"Mean sea level" The National Geodetic Vertical Datum (NGVD) of 1929 or
other datum, to which floodplain elevations shown on the City floodplain
maps are referenced.
"New construction" The development or the "start of construction" commenced
on or after the effective date of this ordinance.
"One-hundred year mean recurrence interval flood" or "lO0-year flood" The
flood mag'aitude being equaled or exceeded at a mean recurrence interval of
once every one-hundred years. The 100-year flood has a one percent chance
of being equaled or exceeded in any given year. See "Base flood" and
"Design base flood."
"Person" Any individual or group of individuals, corporation, partnership,
association, utility, or any other entity, including State, County, City,
Districts or other govern~nental agencies and departments thereof.
"Probable Maximum Flood" (PMt=) The most severe flood likely to occur from
a combination of the most critical meteorological and hydrological
conditions that are reasonably possible in the drainage basin according to
publications of the National Oceanic and Atmospheric Administration.
Usually much greater than the 100-year flood.
"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 without cumulative!y increasing the water surface elevation more than
a desig-nated height.
"Remedy a violation" To bring the structure or other development into
compliance with these, State, or FEMA floodplain management regulations or
if this is not possible, to reduce the impacts of its noncompliance. Ways
that impacts may be reduced include protecting the structure or other
affected areas from flood-related erosion or damages, implementing the
enforcement provisions of the ordinance or otherwise deterring future
similar violations.
"Rivefine" Relatlnff to, formed by, or resembling a river, stream, creek,
brook, etc. (including tributaries).
"Sheet flow area" Overland flow of surface water runoff of shallow depth
and evident velocity. See "Area of sh-~llow flooain~."
"Specia/Flood Hazard Area" (SFHA) The land in the floodplaln area within
the City subject to flooding and shown on a FHBM or FIRM as Zone A, AE, AH,
AO, or A1-99.
"Standard Project Flood" The flood established for the design of levees,
dams, or similar flood protection structures subject to sudden failure by
flood-related erosion. A term used by the US Army Corps of Ex~dneers to
designate the most severe flood considered reasonably characteristic of the
location being evaluated, excluding extremely rare combinations. Generally
40 to 60 percent of the PIV[F for the same location.
"Start of construction" Either the first placement of permanent
construction of a structure on a site, such as the pouring of slab or
footln~s, the installation of piles, the construction of columns, or any
work beyond the stage of excavation; or the placement of a manufactured
home on a foundation, provided the actual start of construction, repair,
reconstruction, placement, or other substantial improvement was within 180
days of the permit issue date. Permanent construction does not include
land preparation, such as clearing, grading and filling; nor does it
include the installation of streets and/or walkways; nor does it include
excavation for a basement, footings, piers or foundations or ~he erection
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 as part of a main structure.
"State" The state of Texas and the Texas Water Commission under the Texas
Floed Control and Insurance Act (Subchapter I of the Texas Water Cc~e).
"Storm cellar" A space below grade used to accommodate occupants of the
structure and emergency supplies as a means of temporary shelter against
severe tornado or similar wind storm activity.
"Structure" A walled and roofed building, a manufactured home, a utility
substation, or a gas or liquid storage tank that is principally above
ground.
"SubstantiaI improvement" Any repair, reconstruction, or improvement of a
structure, the cost of which equals or exceeds 50 percent of the market
value of the structure either:
1. Before the improvement or repair is started, or
2. If the structure has been damaged and is being restored, before the
damage occurred.
For the purposes of this 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. The term does not,
however, include either:
1. Any project for improvement of a structure to comply with existing
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.
"Surety" A corporation surety bond, cash, certificate of deposit, or an
irrevocable letter of credit.
"Ultimate development" The state of full urbanization of all lands within a
watershed based upon known or anticipated land uses as established by city
zoning or master planting land use maps in all cities and jurisdictions
affecting the watershed.
"Use" Any purpose for wkich a building or other structure or a tract of
land may be designed, arranged, intended, maintained, or occupied; or any
activity, occupation, business, or operation carried on, or intended to be
carried on, in a building or other structure or on a tract of land.
"Use perfrEt" The permit required before any use may be commenced.
"Variance" A grant of relief from the requirements of this ordinance which
permits construction in a manner that would otherwise be prohibited by this
ordinance.
t'Violation" The failure of a structure or other development to be fully
compliant with this ordinance. A structure or other development without
the elevation certificate, other certifications, or other evidence as
required by the Administrator, is presumed to be in violation until such
time as that documentation is provided.
"Watercourse" A natural or artificial channel in which a flow of water
occurs either continually or intermittend),.
~Watershed" The area from which water drains to a siz~gle point; in a
natural basin, the watershed is the area contributing flow to a given place
or a given point on a stream,
"Water surface elevation" The height, in relation to the National Geodetic
Vertical Datum (NGVD) of 1929 (or other datum, where specified), of floods
of various magnitudes and frequencies in the floodplains of lacustrine or
riveme areas.
ARTICLE 3
General Provisions
SECTION A. Lands to Which This Ordinance Applies
This ordinance shall apply to all floodplain lands within the
jurisdiction of the City whether or not the land is within an
identified special flood hazards area. Provided, however, this
ordinance shall apply only to projects which have not as of the
effective date of this ordinance, received conditional approval
from (FEMA). Projects which have already been reclaimed under a
prior conditional letter of approval from (FEMA) or which have
received a conditional letter of approval from (FEMA) prior to
the effective date of this ordinance, shall be considered by the
City solely on the basis of regulations in effect at the time of
the issuance of the conditional letter of approval from (FEMA).
SECTION B. Basis for Establishing Floodplains and Special Flood
Hazards
The floodplain areas and areas of special flood hazard are
identified in the scientific and engineering report entitled,
"The Flood Insurance Study for the City of Coppell," dated August
1, 1980, which, with its accompanying FIRM,s and floodways, and
any revisions thereto, is hereby adopted by reference and
declared to be a part of this ordinance. Additional master
planning maps adopted by amendment to this ordinance and on file
in the Floodplain Administrator's Office shall also be considered
to be a part of this ordinance.
SECTION C. Establlshment of a Floodplain Development Permit
A Floodplain Development Permit shall be required for all new
construction and development, including the placement of
manufactured homes, within the floodplain management areas of the
City to ensure conformance with the provisions of this ordinance.
SECTION D. Penalties for Noncompliance
No structure or development of land shall hereafter be
constructed, located, extended, converted or altered without full
compliance with the terms of this ordinance and other applicable
october 16, 1987 - Page 18
FLOODPLAIN MANAGEMENT ORDINANCE
Revised - Ginn, Inc.
regulations. Violation of the provisions of this ordinance by
failure to comply with any of its requirements (including
violations of conditions and safeguards established in connection
with conditions) shall constitute a misdemeanor. Any person who
violates this ordinance or fails to comply with any of its
requirements shall upon conviction thereof be fined not more than
Two Hundred Dollars ($200.00) for each violation, be required to
correct or remove the noncompliance, and each and every day such
violation is continued shall constitute a new and separate
violation. Nothing herein contained shall prevent the City from
taking such other lawful action as is necessary to prevent or
remedy any violation.
SECTION E. Repealing Clause
In addition to the purposes outlined in Article 1, this ordinance
replaces the former City of Coppell Ordinance No. 219 with
floodplain management guidelines which, except as hereinabove
provided in Section A of this Article, repeal the former
ordinance. All provisions of all other ordinances conflicting
with the provisions of this ordinance are hereby repealed. All
other ordinances and provisions of such ordinances not expressly
in conflict with the provisions of this ordinance shall remain in
full force and effect.
SECTION F. 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.
SECTION G. 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.
October 16, 1987 - Page 19
FLOODPLAIN MANAGEMENT ORDINANCE
SECTION H. Warning and Disclaimer of Liability
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 ultimate
development floodplains or special flood hazard areas 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, any officer
or employee thereof or the Federal Insurance Administration or the Federal
Emergency Management Agency, for any flood damages that result from
reliance on this ordinance or any administrative decision lawfully made
thereunder.
SECTION I. 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 validi~ 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 invalidit-/ have any effect on any
other ordinances or provisions of ordinances of the City of Coppell.
ARTICLE 4
Administration
SECTION A. Designation of the Floodplain Administrator
The City Engineer is hereby appointed Floodplain Administrator to
admLn.ister and implement this ordinance and other appropriate sections of
4z[ CFR (National Flocd Insurance Program Regulations) by granting or
denying development permit applications in accordance with its provisions
pertaining to floodplain management. He shall serve at the pleasure of the
City Council. His successor shall be appointed by resolution of the City
Council.
SECTION B. Duties and Responsibilities of the Floodplain Administrator
Duties of the Floodplain Administrator shall include, but not be limited to
the following:
1. Assure compliance with the minimum floodplain management requirements
of the State and Federal governin~ agencies.
2. Establish. evaluate, disclose and maintain procedures for
implementation and enforcement of this ordinance and compliance with
these floodplain management regulations.
3. Permit only that development within floodplain management areas which
meets planning considerations that:
a. Meet the minimum criteria and requirements of this ordinance;
b. Are appropriate in light of the probability of flood damage and the
need to reduce flood losses;
c. Meet acceptable social and economic use of the land in relation to
the baT~rds involved; and
d. Do not increase the d~n_.~er to human life.
4. Prohibit nonessential or improper installation of public utilities and
public facilities in floodplain areas.
5. Prohibit the placement of any nonessential storage, manufacturing,
industrial plants or facilities Within a floodplain management area.
6. Consider alternatives to development within floodplain areas; make
recommendations for the continuation of City development which include
consideration for human safety and diversion of development to areas
safe from flooding in light of the need to prevent environ. mentally
incompatible floodplain use; and encourage floodproofing of existing
floodplain developments.
7. Make full disclosure to all interested parties that:
a. CertAin structures are located within floodplain areas;
b. Variances have been granted for certain developments or structures;
and
c. Data are available which show special flood hazard area and
floodplain management area information for the City.
8. Prepare and maintain flood warning and emergency preparedness plans
which include:
a. Provision for alternative vehicular access and escape routes; and
b. Minimum floodproofing and access requirements for schools,
hospitals, nursing homes, orphanages, penal institutions, fire
stations, police stations, commumcations centers, water and sewage
puznpi.ug stations, and other public or quasi-public facilities to
enable them to withstand flood damage, and to facilitate emergency
operations.
9. ~nforce improvements to local drainage within new developments to
control increased runoff that might increase the danger of flooding to
users of the development or of flood hazards to users or other
properties adjacent to, downstream or upstream of the development.
10. Coordinate City floodplain management programs with State, regional and
neighboring community floodplain m~n~gement programs.
i1. Require Floodplain Development Permits for all new construction or
development in all Hoodplain management areas of the City.
a. Assure that conditional approvals are received from FEMA before a
Floodplain Development Permit is issued. Upon written
acknowledgment of receipt by FEMA of the required technical data,
construction may commence within a floodplain area provided the
person performing such development furnishes a written agreement to
assume the cost of any modifications noted by FEMA, as a result of
their tech.~cal reviews, to be required for proper completion.
b. Require the developer to submit an as-built technical report of
floodplain development conditions as soon as work affecting the
floodplain is completed. Encourage the expeditious submittal of
the as-built conditions in order to obtain the final letters of map
revision from the FEMA.
12. Make submittals to the FEM_A in compliance with the provisions of this
ordinance and the provisions of ~4 CFR.
13. Maintain and hold open for public inspection all records including
maps, elevation certificates of eligibility, elevations and
floodproofing, permits issued, variances, appeals, and so on, as
required by or generally pertaining to the provisions of this
OrdinanCe.
14. Review, approve or deny all. appL~,cations for development permits
reqllired by adoption of this ordinance.
15. Make Luterpretations as Deeded to determine the exact location of the
botmdaries of tloodplain maz~agement areas or special flood hazard
areas.
16. Notify the affected communities and the Texas Water Commission prior to
any alteration or relocation of a watercourse, and submit evidence of
such notification to the Federal Emergency Management Agency.
17. Obtain and reasonably utilize base flood elevation data and floodway
data available from a Federal, State, or other source, when those data
have not been provided as outlined in Article 3, Section B, in order to
administer the provisions of Article 5-
SECTION C. Floodplain l~velopment Permit
A Floodplain Development Permit shall be required for all new construction
and development, including the placement of manufactured homes, within the
floodplain management areas of the City. Application for a Floodplain
Development Permit shall be presented to the Floodplain Administrator on
City permit forms or facsimiles thereof, which include drawings and
technical information sufficient to fully support the compliance of the
proposed development with the provisions of this ordinance. These data
shall include, but are not necessarily limited to information which
demonstrates the effects of such development on the floodplain including
impacts on the floodplains, floodways, flood elevations, and velocities
within the channel of the 2-year and 100-year mean recurrence interval
floods and in the discharges of the effective FIS upstream of, downstream
of, and along or through the proposed development, and, further, the person
making application shMl:
a. Show the lowest floor be elevated to a minimum of two (2) feet
above the FIS base flood elevation or to one (1) foot above the
design base flood elevation, whichever is higher. In locations of
assumed critical depth, the energy gradient shall be used to
establish these respective minlrn,~rn lowest floor elevations.
b. Furnish delineations of existing and post-development floodplains.
c. Demonstrate, with technical data, the impacts on the design base
flood storage capacity of the floodplain for all developments which
include fill within the floodplain.
d. Demonstrate with technical data that the flood carrying capacity
within the altered or relocated portion Of any watercourse is
msintailled.
e. Demonstrate with tectmical data that, at any point within the City,
the cumulative effect of the proposed development when combined
with all other existing and approved proposed development:
(1) Will not increase the water surface elevations of the design
base ~oc~t;
(2) Will not increase the effective FIS base fl(xxi elevations by
more than one foot;
(3) Will not increase the base flood water surface elevations of
the FIS reg'ulatory floodway in effect at the time of
application for a floodplain development permit; and
(4) Otherwise meets the provisions of Article 5 of this ordinance.
f. Prepare technical data for the Floodplain Administrator's review
and submittal to the FEMA.
g. Affirm that all necessary permits have been obtained from those
Federal (including Section a of the Federal Water Pollution
Control Act), State, and other local governmental agencies from
which prior approval is required.
SECTION D. Vari~,~ces
1. Appeal Board The Appeal Board will hear and decide appeals and
requests for variances from the requirements of this ordinance. The
City Council will serve as the Appeal Board unless a specific Appeal
Board is otherwise appointed by ordln~nce.
2. Variance Procedures
a. The Appeal Board shall hear and render judgemerit on an appeal when
it is alleged there is an error in any requirement, decision or
determination made by the Floc~tplain Administrator in the
e~.forcement or administration of this ordinance.
b. My person aggrieved by the decision of the Appeal Board may appeal
such decision in the courts of competent jurisdiction.
c. The Fleodpl3in Administrator shall report any variances, including
the justification for their issuance, to the Federal Emergency
Management Agency upon request.
Variance Conditions
a. Variances shall not be issued within any designated floodway if any
increase in flood levels during the effective FIS base flood
discharge would result.
b. Variances may be issued for new construction and substantial
improvements and for other development necessary for the conduct of
a functionally dependent use provided that all other conditions of
this section (Section D of Article 4) are met, and that the
structure or other development is protected by methods that
minimize flood damages during the base flood and create no
additional threats to public safety.
c. Variances may be issued for the reconstruction, rehabilitation or
restoration of structures listed on the National Register of
Historic Places or the State Inventory of Historic Places, without
regard to the procedures set forth in the remainder of this
ordinance.
d. Variances may be issued for new construction and substantial
improvements to be erected on a lot of one-half acre or less in
size contiguous to, and surrounded by, lots with eXistin~
structures constructed below the base flood level, for cases of
exceptional hardship, providing the other relevant factors in Sub-
section 60.6 of 44 CFR 1.1 have been fully considered. Variances
for lot sizes greater th~n one-half acre contiguous to, and
surrounded by, non-complying lots will only be considered with
appropriate technical justification.
e. Upon consideration of the factors noted, and the intent of this
ordinance, the Appeal l~ard may attach such conditions to the
grantb~.~, of variances as it deems necessary to further the purpose
and objectives of tiffs ordinance.
4. Prerequisites for Granting Variances
a. Variances shall only be issued upon a determination that the
variance is the minLmum necessary, considerin2 the flood hazard, to
a.fl~ord relief.
· . ~ , b. Variances shall only be issued upon:
(1) Showing a good and sufficient cause;
, '[2) A determination that failure to grant the variance would result
,T. 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
safer/, extraordinary public expense, create nuisances, cause
fraud on or victimization of the public, or a conflict with
existing local laws or ordinances.
c. Any applicant to whom a variance is granted shall be given written
notice that the structure will be permitted to be built with the
lowest floor elevation below the base blood elevation, and that the
cost of flood insurance will be commensurate with the increased
risk resulting from the reduced lowest floor elevation.
ARTICLE 5
Standards, Provisions, Methods, and Criteria for Flood Hazard Reduction
These standards, provisions, methods, and criteria shall apply in all
floodplain management areas including areas of special flood hazards and
all watercourses originating within or flowing within, through or along the
City limits of the City of Coppell for riverme and lacustrine areas
whether or not the land is within an identified special flood hazards area
.: and in all areas of potential shallow flooding or sheet-flow flooding,
-. regardless of watershed size.
All drawkngs and technical submittals for work within flo<~dplain management
areas shall ba accompanied by certifications by a registered engineer,
architect. or: ~:z-veyor, as applicable, that the data presented are accurate
to the best of the certifier's knowledge. Technical data certifications
shall include a statement that analyses have been performed correctly and
in accordance with sound engineering practices.
SECTION A. General Standards
The following general standards shall be required for all new construction,
development, or substantial improvements:
1. Designed or modified to be adequately anchored to prevent: flotation,
collapse, or lateral movement of the structure resulting from
hydrodynamic and hydrostatic loads, including the effects of buoyancy;
2. Constructed by methods and practices that minimize flood damage;
3- Constructed with materials resistant to flood damage;
4. Constructed with electrical, heating, ventilation, plumbing, and
conditioPing equipment ,rid other service facilities that are designed
and/or located so as to prevent water from entering or accumulating
within the components during conditions of flooding;
Water supply systems (izlcluding all replacement systems) shall be
designed to minimize or eliminate infiltration of flo<xt waters into the
system;
Sanitary sewage systems (including replacement systems) shall be
designed to minimize or eliminate infiltration of flood waters into the
system and discharge from the systems into flood waters;
On-site waste disposal systems shall be located to avoid impairment to
their operation or contamination from them during flooding; and
Design stzndards of all f~c'ilities shall be in accordance with the
provisions of the "Subdivision Ordinance of the City of Coppelf."
r~CTICLN tL ,Sp~ific Smdards
In all flcx~dplain management areas where base flood, design base flo<xi and
special flood hazard area data have been provided, the following specific
standards shall be required for all new construction, development, or
substantial improvements. Where adequate base flood data are not
available, the same specific standards of this section are required;
however, the developer shall first determine the ultimate development 100-
year floodplain for a sufficient distance to fully evaluate the impacts
downstream, through or along, and upstream of the proposed development and
present the facts, figures, and results of · techn/cal study in a level of
detail and scope of coverage similar to the guidelines outlined in Chapter
3 of FEMA document 37, "Flood Insurance Study Guidelines and Specifications
for Study Contractors," September, 1965.
i. Residential Construction
a. The lowest floor (including basement) shall be elevated a minimum
of two (2) feet above the FIS base flc~xi elevation or to one (1)
foot above the design base flood elevation, whichever is higher.
In locations of assumed critical depth, the energy gradient shall
be used to establish these respective miramum lowest floor
elevations.
b. In areas of shallow flooding (AO/AH Zones), the lowest floor
(including basement) shall be elevated above the highest adjacent
grade at least as kigh as the depth number specified in feet on the
FIRM or a minimum of 2 feet, whichever is higher.
c. A registered professional engineer, architect, or land surveyor
shall submit a certification to the Floodplain Administrator that
the standards of this subsection are satisfied.
NonresidenTial Construction
~L Any cm'nmercial, industrial Dr other nonresidential structure shall
either have the lowest floor (including basement) elevated to a
_ minimum of 2 feet above the base flood level or, together with
~' attendant utility And . ~mitary facilities, be designed so that
below the bas~ E~ level, the structure is watertight with walls
-sub~antially impermeable to the passage of water and with
structural components having the capability of resisting
hydrostatic and hydrodynamic loads and effects of buoyancy.
b. Nonresidential structures located in areas of shallow flooding
(AO/AH Zones) shall either have the lowest floor (including
basement) elevated above the highest adjacent grade at least as
high as the depth number specified in feet on the FIi~M or a minimum
of 2 feet, whichever is higher; or, together with attendant utility
and sanitary facilities, be designed so that below the base flood
level, the structure is watertight with walls substantially
impermeable to the passage of water and with structural components
having the capability of resisting hydrostatic and hydrodynamic
loads and effects of buoyancy.
c. A registered professional engineer or architect, as applicable,
sh~ll develop and/or review structural design, specifications and
plans for the construction, and shall certify that the design and
methods of construction are in accordance with accepted standards
of practice as outlined in this subsection.
d. A record of the certification by a registered professional engineer
or architect shall be filed with the Floodplain Administrator.
3. Utilities, Bridges, Roadways and other Public Use Facilities
a. All public utilities including operational pumps, transformers,
switchin~ equipment, and related mechanical and electrical
equipment and facilities for sewer, water, gas, electrical, and
commtmication systems shall be located and constructed to minimize
or eliminate infiltration and damage during flooding conditions.
b. All public utility equipment and bridges shall be designed to
remain operable and accessible with a minimum of 2 feet of
freeboard above adjacent base ilood elevations or 1 foot above
design base flood elevations, whichever is higher.
c. Roadways ~nd parking lots shall be designed to remain usable and
, accessible with adequale elevation above the base flood as follows:
(I) A freeboard to the lowest top of curb of two feet in the
· effective FIS base flood or one foot in the design base flood,
whichever elevation is greater, for Freeways and Major and
Minor Arterials.
(2) A freeboard to the lowest top of curb of oae foot in the
effective FIS base flood or the design base flood, whichever
elevation is greater, for Collector Streets.
(3) A minimum pavement flow-lin4· elevation no lower than the
effective FIS base flood 'or the design base flood, whichever
elevation is greater, for Residential Streets and for Parking
Lots.
d. Provisions for the containment, treatment and/or removal and
disposal of possible spillage or discharge of fuels, hazardous
materials, or wastes related to the operation or maintenance of
public utilities shall be clearly identified in construction
drawings and an emergency operations plan, or an assessment of
impacts of release of pollutants of any kind. shall be prepared and
approved by the Floodplain Administrator.
e. All other provisions of non-residential construction shall apply to
public utilities and facilities, including affirmation by a
registered engineer that all necessary permits have been obtained
as reqtnred by Article 4.
4. Enclosures
a. Fully enclosed areas below the lowest floor that are subject to
flooding shall be designed to automatically equalize hydrostatic
flood forces on exterior walls by allowing for the entry and exit
of floodwaters.
b. Designs for meeting this requirement must be certified by a
. registered professional engineer or architect, or meet or exceed
the following minimum criteria:
(1) A rnln~I2111~ of two openings having a total net area of not less
:than one square inch for every square foot of enclosed area
subject to flooding ~halt be provided.
(2) The bottom of all openings shall be no higher thsu one foot
above grade.
(3) Ope-~nSs may be equipped with screens, louvers, valves, or
other coverqs or devices provided that they permit the
automatic entry and exit of floodwaters.
5. Manufactured Homes
a. Require that all manufactured homes to be placed or substantially
improved within a special flood hazards area be elevated on a
permanent foundation such that the lowest floor of the manufactured
home is a rn{nimum of 2 feet above the base flood elevation or to 1
foot above the design base flood, whichever is higher,. and be
securely anchored to an adequately anchored foundation system in
accordance with the provisions of Section A of this Article 5.
b. Manufactured homes shall be in compliance with Section B.1 of this
Article 5.
6. Floodways
a. Encroachmerits are prohibited within designated floodways, including
fill, new construction, substantial improvements and other
development unless certification by a registered professional
engineer is provided demonstrating that equal conveyance
encroachmerits do not result in any increase in flood levels at any
floodplain location and that all other provisions of this ordinance
are met during the occurrence of the base flood discharges.
b. When a floodway has not been designated, no new construction,
substantial improvements, or other development (including fill)
shM1 be permitted within the 100-year floodplain until it is
demonstrated that either:
( 1 ) The cumulative effect of the proposed development, will not
increase the water surface elevation of the design base flood
mnre than ~ne foot above the August, 1980, FIS, or above the
-most ,:m-rent effective Flood Insurance Study base ~o~d
etevaticms. whichever is less, at any point within the stream;
OF,
(2) The cumulative effect of the proposed development, will not
increase the water surface elevation of the design base flood
at any point in the stream above that which would occur without
the proposed development.
· SECTION C. Standards for Subdivisions
i. All subdivision proposals, including manufactured home parks and
subdivisions, shall be consistent with all other conditions of this
ordinance including the requirements of Article 3, Article 4, and the
provisions of all ~ections of this Article 5.
2. Base flood (including design base flood) elevation data shall be
generated for subdivision proposals and other proposed development
includ~n~ manufactured home parks and subdivisions if not otherwise
provided.
3. All subdivision proposals including manufactured home parks and
subdivisions shall have adequate drainage provided to reduce exposure
to flood hazards.
4. All subdivision proposals must have the following note placed on the
preliminary and final plat:
"Floodplain Development Permit Application No. has
been filed with the City of Coppell Floodplain Administrator on
, 19 .
Floodplain Administrator,
, Date."
5. All subdivision proposals shall have the boundaries of the 100-year
floodplain and floodway clearly shown on the preliminary and final
plat.
6. All lots within or adjacent to the 100-year floodplain shall have the
lowest floor elevation for each building site shown on the site grading
plans.
7. When any part of a subdivision lies within or adjacent to the 100-year
floodp)~in, a permanent bench mark tied to a designated National
Geodetic Vertical Datum marker shall be established witkin the
subdivision at an accessible location. The bench mark and tie shall be
located and referenced with all pertinent information on the final plat
along with a registered public surveyor's seal.
8- When any part of a completed subdivision is to remain within or
adjacent to the 100-year floodplain, the following note must be placed
on the f~n~) plat:
"The developer, builder, seller, or agent shall inform in writing, each
prospective buyer of sulxlivision lots or property located within
special flood haT~rd areas of this site that such property is in an
identified flood ~Tard area and that all development must conform to
the provisions of the City of Coppell Floodplain Management Ordinance.
The written notice shall be filed for record in the county Deed of
Records and a copy of the notice must accompany the application for
development permit."
9. All structures placed in areas subject to shallow flooding (AO/AH
Zones) or in low areas where ponding of surface runoff or sheet-flow
flooding may occur, shall have the lowest floor (including basement)
placed at the F17{M specified depth number (in feet if specified), or a
minimum of 2 feet above the highest adjacent grade, whichever is
higher. Where the direction of sheet flow is towards a building, all
areas around the structure shall be sloped away from the structure and
the site graded to direct the flow around and away from the structure.
SECTION D. Engineering Criteria for Floodplain Management
In addition to the provisions of the general and specific standards of this
ordinance, the following engineering criteria shal~ apply tO all
development within riveme or lacustrine floodplains of the City:
1. Design discharges for evaluation of rivefine floodplains in the City of
Coppell shall be based on three discharges at the design point, and, in
the case of flood protection by levees, a fourth discharge shall be
included for design of the levees, as follows:
a. Tl~e "mean ~,~nual flo<3d;" defL~ed for purposes of this ordinance as
the discharge having a 50% probability of being equaled or exceeded
in a given year (approximately the 2-year mean recurrence interval)
as detemined by historical data or regional regression equations
of the State Department of Highways and Public Transportation;
b. The design base flood discharge; defined as the discharge having a
1% probability of being equaled or exceeded in a given year (the
100-year mean recurrence interval) from a fully developed
watershed. Discharges shall be determined by hydrograph methods
for areas larger th~n 0.25 square miles, by either hydrograph
methods or rational formula methods for areas from 6 acres to 0.25
square miles and by the rational formula methods at locations
having less than 5 acres of contributing area.
c. The low-flow or base-flow discharge; defined as the dry weather
flow as determined by historical data or assumed to be no less than
5 csm in this ordinance.
d. The standard project flood; defined in this ordinance as the flood
which would occur in the event of a 50% PM~F as determined by an
evaluation of the probable maximum precipitation as outlined in
Hydrometeorological Reports 51, "Probable Maimurn Precipitation
Estimates, United States East of the 105th Meridian" and 52,
"Application of Probable Maximum Precipitation - Ura'ted States East
of the 105th Meridian."
2. Alterations of the channel or adjacent floodplain shall not cause the
average channel velocities during the mean annual flood 1o exceed
maximum permissible velocities upstream or downstream of the project
site.
3. Alterations of the channel or adjacent floodplain shall not result in
any increase in water surface elevation, on site, upstream nor
downstream of the project site in the fully developed watershed design
base flood discharge.
4. No alterations shall occur to the low-flow channel in park or green-
belt areas except as provided for in an approved master plan. If
structural pilot channels are approved, the low-flow discharge shall be
fully contained within the pilot channel with 6 inches of freeboard.
5- Flood protection offered by proposed levees shall be designed based on
the standard project flood plus three feet of freeboard.
6. Alterations of the channel or adjacent floodplain shall not result in
average design base flood velocities which exceed the maximum
permissible velocities of this ordinance on site, upstream or
downstream of the project.
a. If off-site velocities in the natural channel are erosive, no
increase in velocity shall result at the upstream or downstream
erosive velocity location. No exceptions will be made for
increases in erosive off-site velocities except as approved by the
floodplain administrator.
b. Exceptions to this rule will be made for erosive velocities within
on-site channels for aesthetic or environmental considerations if
it can be shown that such velocities are in the best aesthetic or
environmental interest, provided sufficient area is designated for
flood-related erosion which will occur in the high velocity reach
and provided no structures will be adversely affected by such high
velocities.
7. Alterations of the floodplain shall occur only if it can be shown that
equal conveyance alterations can occur on both sides of the channel and
that all other provisions and criteria of this ordinance are met.
8. Design of lakes, ponds, stock tanks, detention, or detention/retention
facilities shall be based on the discharges and other requirements of
the Texas Water Commission.
9. Permit applications shall be made to the Floodplain Administrator as
outlined in Section C, Article 4, for alterations of the channel or
adjacent floodplain and shall include, as a minimum:
a. Hydrologic and hydraulic analyses clearly defining existing
conditions, proposed conditions and impacts of the project,
including work maps and stream profiles upstream and downstream of
the site for sufficient distances to demonstrate a match to
existing conditions for at least 3 consecutive cross-sections.
b. A site gradLng and drainage plan showLug proposed cut slopes, fill
slopes, on-site contours, returns to adjacent property contours,
existing contours, and the existlns and proposed 100-year flood
inundation lines.
c. The site plans shall include a delineation of landscaped areas
showing the general type and extent of landscape materials proposed
to remain or be placed within the floodplain.
d. A narrative or plan shall be provided which depicts temporary and
permanent erosion controls to protect disturbed and post-
development floodplain overbank or channel areas:
(1) During the period it takes to establish temporary or permanent
vegetative cover; and
(2) To prevent flood-related erosion during the establishment
period and to minimize long term flood-related erosion.
e. A narrative describing maintenance requirements to sustain the
assumed Manrting's "n" values of the technical report data for any
channel improvements, the estimated frequency of maintenance, how
these maintenance requirements are to be accomplished, by whom, and
at what anticipated costs.
f. Other such materials as may be required to clearly define the
project location, scope, and intended use.
g. Evidence of water rights and dam safety permits from the Texas
Water Commission shall be submitted to the Floodplain Administrator
before water can be impounded in any lacustrine system.
ARTICLE 6
Effective Date
This ordLaance shall take effect immediately from and after its passage and
the publication of the caption as the law in such cases provides.
DULY PASSED by the City Council of the City of Coppell, Texas, on the
day of (f')~..-4'~/914~. , 19 a° '7 ·
APPROVED:
/-
/
ATTEST:
APPROVED AS TO FORM:
CITY ' AT T ORNEY