OR 94-639 Provide comprehensive management of floodplains AN ORDINANCE OF THE CITY OF COPPELL
ORDINANCE NO. 94639
AN ORDINANCE OF THE CITY OF COPPELL, TEXAS, AMENDING THE CODE
OF ORDINANCES OF THE CITY OF COPPELL, TEXAS, BY AMENDING ARTICLE 16-
4, FLOODPLAIN MANAGEMENT ORDINANCE; PROVIDING FOR COMPREHENSIVE
MANAGEMENT OF FLOODPLAINS IN THE CITY OF COPPELL; PROVIDING 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 NOT TO EXCEED FIVE
HUNDRED DOLLARS ($500.00) 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; DEFINING DUTIES AND RESPONSIBILITIES OF
THE ADMINISTRATOR; MAKING GENERAL AND SPECIFIC DESIGN AND
PERFORMANCE PROVISIONS FOR METHODS OF REDUCING LOSSES; PROVIDING
FOR THE REPEAL OF ORDINANCE 87-390 AND ALL ORDINANCES IN CONFLICT;
PROVIDING A SEVERABILITY CLAUSE; PROVIDING A SAVINGS CLAUSE; AND
PROVIDING AN EFFECTIVE DATE.
BE IT ORDMNED BY THE CITY COUNCIL OF THE CITY OF COPPELL, TEXAS:
SECTION 1. That the Coppell City Code be, and the same is hereby, amended by
amending Article 16-4 to read as follows:
"ARTICLE 16-4 FLOODPLAIN MANAGEMENT ORDINANCE
ARTICLE 1
Adoption and Title, Statutory Authority, Findings of Fact, Purposes and Methods,
Scope of Authority, and Organization.
SECTION A. Adoption and Title
This Ordinance is hereby adopted and shall be known as the "Floodplain Management
Ordinance" of the City of Coppell.
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SECTION B.
Statutory Authority
The Legislature of the State of Texas has in the Local Government Code and Water
Code Section 16.3 11 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 minimizing exposure to
flood losses. Therefore, the City Council of the City of Coppell, Texas has enacted
this ordinance to establish such regulations.
SECTION C.
Findings of Fact
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
flood 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 cause of these flood losses are the cumulative effects of:
Obstructions in areas of special flood hazards which increase flood
heights and velocities, and when improperly placed, damage uses in
other areas;
b. Uses that are inadequately floodproofed, elevated or otherwise
protected from flood damage;
Quick intense overflows of water resulting from combinations of steep
slopes, short drainage basins, and high proportions of surfaces
impervious to water and unable to absorb runoff;
Modifications to drainage patterns and displacement of natural
vegetation with nonporous surfaces for buildings, roads, and parking;
and
Lack of comprehensive basin-wide planning to manage the riverine
floodplains in order to reduce the losses incurred when the inevitable
flooding takes place.
The riverine areas of the City are a valuable resource to the citizenry in that
they provide focal points for development, recreational opportunities, and
aesthetic enjoyment potential.
As valuable resources and as flood hazard areas, the riverine systems of the
City should be managed for the welfare of the citizenry.
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SECTION D. Purposes and Methods
It is the purpose of this 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. Minimize expenditure of monies for costly flood control projects;
3. Minimize 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. Minimize 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 secondary uses and
development of floodplain areas (the primary use being conveyance of
floodwaters);
7. Insure that potential buyers are notified that property is in an area of special
flood hazard;
8. Insure that those who occupy the areas of special flood hazard assume
responsibility for their actions;
9. Restrict or prohibit uses which are dangerous to health, safety, and property
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 facilities 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
divert 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 property 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. Organization of this Ordinance
This ordinance is organized into six 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 manage and regulate the development along and within
floodplains.
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 City of Coppell has other ordinances, regulations,
and standards and specifications directly or indirectly pertaining to drainage and
storm sewer facilities and design requirements. These include but are not limited to
the following: City of Coppell Zoning Ordinance; City of Coppell Subdivision
Ordinance; City of Coppell Park, Recreation and Open Space Master Plan; City
Wide Storm Water Management Study; the City of Coppell Comprehensive Plan, and
related standards among others. Developers, builders, engineers, or others involved
with new construction or development of lands in the City of Coppell should refer
to these documents and to the Code of Ordinances of the City of Coppell, Texas for
additional requirements and information concerning stormwater drainage facilities.
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ARTICLE 2
Definitions
Unless specifically defined below, words or phrases used in this ordinance shall be
interpreted so as to give them the meaning they have in common usage for floodplain
management purposes to give this ordinance its most reasonable application.
'~ldministratot' see "Floodplain Administrator."
'~lppeaF A request for a review of the interpretation of any provision of this
ordinance or a request for a variance.
'L4ppeal Board' 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.
'?lppurtenant structure" A structure which 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.
'~,lrea of shallow flooding' A designated AO or AH Zone on the Flood Insurance
Rate Map (FIRM) with a one percent or greater annual chance of flooding to an
average depth of one (1) to three (3) feet where a clearly defined channel does not
exist, where the path of flooding is unpredictable and where velocity flow may be
evident. Such flooding is characterized by ponding or sheet flow.
'~lrea ofspecial~ood 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, A1-99, 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.
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"Badn" The total area from which surface runoff is carried away by a drainage
system. Comparable terms in common usage include "drainage area," "catchment
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 wa//" 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.
"Bu//d/ng" See "Structure."
"cfs" 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.
"Critical feature" An integral and readily identifiable part of a riverine, lacustrine, or
flood protection system, without which the natural or intended operation provided
by the entire system would be compromised.
"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.
"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 urbanized watershed to establish a flood which may
include, but is not necessarily limited to, low flows, base floods, 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 flood' The one-hundred year mean recurrence interval (100-year) flood
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 100-year
precipitation event will produce a 100-year runoff event.
"Development" Any manmade change to improved or unimproved real estate
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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 permR" See "Floodplain development permit."
"Elevated building' A building located in SFHA Zones A1-99, AE, A, AO, AH, 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 the 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 unimpeded movement of flood waters.
"Encroachment" Any activity in a floodplain which hinders the passage of water or
othenvise affects flood flows; e.g. fill, buildings, fences and so on. A Floodplain
Development Permit is required for all encroachments.
"Enc/osure" 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 which will begin to
cause erosion of the parent materials of the channels, overbanks, or areas of shallow
flooding. See "Maximum permissible velocity."
"Equal conveyance alteration" 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.
"Existing conditions" The floodplain conditions established by a flood elevation study
based on land use as of the date of the study completion.
"Existing construction" Structures for which the "start of construction" commenced
before August 1, 1980. "Existing construction" may also be referred to as "existing
structures."
"~ structures" See "Existing construction."
"Federal Emergency Management Agency" (FEMA) The Federal agency which
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administers the National Flood Insurance Program.
"Hood" or ']/ood/ng" A general and temporary condition of partial or complete
inundation of normally dry land areas from water from any source causing:
The overflow of waters normally contained within stream banks, open or
closed channels, lakes, ponds, tanks or other storage areas; and/or
2. The unusual and rapid accumulation or runoff of surface waters.
"Flood elevation detertn/na//on" 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 existing 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
regulatory 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 which the Federal Insurance
Administration has delineated both the areas of special flood hazards and the risk
premium zones applicable to the City.
"Flood Insurance 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" ')7.oodplain land" or 'ytood-prone area" Any normally dry 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.
"FloodplainAdministratot' The City Engineer of the City of Coppell is the floodplain
administrator for all purposes of this ordinance.
"Floodplain Development Permit" A permit which must be obtained by any person
before any development begins on land within a floodplain. See "Development" and
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"Encroachment".
"Floodt'tm_"~ 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.
"F/oodp/a/n management area" The combination of all floodplain and regulatory
floodways within the jurisdiction of the City, including floodplain land that is not
identified on Flood Hazard Boundary Maps or Flood Insurance Rate Maps.
"F/oodp/a/n management regu/at/ons" 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, or 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, changes,
or adjustments to structures which reduce or eliminate flood damage to real estate
or improved real property, water and sanitary facilities, structures and their contents.
"Flood-related erosion" The collapse or subsidence of land along the rivefine 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 rivefine 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 floodplain management regulations.
"Hoodway" See "Regulatory floodway."
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"Floodway encroachment lines" The lines marking the limits of the regulatory floodway
on Federal, State and City floodplain maps.
"44 CFR" The National Hood Insurance Program Regulations, Chapter 1, Subchapter
B, of 44 Code of Federal Regulations. Copies are available from the Texas Natural
Resource Conservation 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 than 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.
"Funct/ona//y depetu/ent use" A use which cannot 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.
"Independent scientific body" A non-federal technical or scientific organization
involved in the study of land use planning, floodplain management, hydrology,
geology, geography, or any other related field of study concerned with flooding.
"Lacustr/ne" Of or pertaining to natural or manmade lakes, ponds, or reservoirs.
"Land use zon/noa' 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 F/oor" The lowest floor of the lowest enclosed area of a building (including
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basement). An unfinished or flood resistant enclosure, usable solely for parking of
vehicles or building 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.
"Manufactured Home Park or Subdivision" A parcel (or contiguous 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
(FIRM) or other official floodplain map of the City approved by the Administrator
or issued by the Federal Emergency Management Agency.
"Maffmum permissible 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 shall be based
on the maximum permissible velocities of the City of Coppell Subdivision Ordinance.
"Mean annual flood' Generally defined as the flood having a mean recurrence
interval of approximately 2.33 years; defined for purposes of this ordinance as the
discharge having a 50% probability of being equaled or exceeded in a given year (the
2-year mean recurrence interval).
"Mean sea lever' The National Geodetic Vertical Datum (NGVD) of 1929 or other
datum, to which floodplain elevations shown on the City floodplain maps are
referenced.
"New comn" 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" 100-year flood" The flood
magnitude 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."
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"Person" Any individual or group of individuals, corporation, partnership, association,
utility, or any other entity, including State, County, City, districts or other
governmental agencies and departments thereof.
"Probab/e Max/mum F/oat/" (PMF) 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 lO0-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
cumulatively increasing the water surface elevation more than a designated 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.
"R/vet/he" Relating 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 shallow flooding."
"Special Flood Hazard Area" (SFHA) The land in the floodplain 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 U.S. Army Corps of Engineers 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 PMF 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 footings, the installation of piles,
the construction of columns, or any work beyond the stage of excavation; or the
placement of a manufactured home on a foundation, 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
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land preparation, such as clearing, grading and filling; nor does it include excavation
for a basement, footings, piers or foundations or the 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 Flood
Control and Insurance Act (Subchapter I of the Texas Water Code).
"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 actMty.
"Structure" A walled and roofed building, a manufactured home, a utility substation,
or a gas or liquid storage tank that is principally above ground.
"Substantial 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
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 the alteration affects the external dimensions
of the structure. The term does not, however, include either:
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
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
planning land use maps in all cities and jurisdictions affecting the watershed.
"Use" Any purpose for which a building or other structure or a tract of land may be
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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 permit" 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.
"Fto/at/on" 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 charmel in which a flow of water occurs either
continually or intermittently.
"Watershed' The area from which water drains to a single 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 riverine areas.
ARTICLE 3
General Provisions
SECTION A.
Lands to Which This Ordinance Applies
This ordinance shall apply to ail 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 map revision
(CLOMR) 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 CLOMR from FEMA. Projects which have received a CLOMR from
FEMA, but have not begun reclamation, shall be considered by the City solely on the
basis of regulations in effect at the time of the issuance of the CLOMR, provided
that the reclamation begins within two years of the date of the CLOMR. If the
reclamation does not begin within two years, the initial CLOMR will be ruled invalid
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and a new CLOMR will be required from FEMA that is in compliance with this
ordinance.
SECTION B.
Basis for Establishing Floodplain 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 April 15, 1994 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.
Establishment of a Floodplain Development Permit
A Floodplain Development Permit shall be reqnired for all new construction,
development, and encroachment 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 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 five hundred
dollars ($500.00) 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
Coppell Ordinance No. 87390 and 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,
15 A6005228
covenants or deed restrictions. However, where this ordinance and other ordinances,
easements, covenants or deed restrictions 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,
Deemed neither to limit nor repeal any other powers granted under State
statues.
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 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 Coppell.
SECTION J.
Savings Clause
An offense committed before the effective date of this ordinance is governed by the
prior law and the provisions of the Code of Ordinances, as amended in effect when
the offense was committed and the former law is continued in effect for this purpose.
16 AGG05228
ARTICLE 4
Administration
SECTION A.
Designation of the Floodplain Administrator
The City Engineer is hereby appointed Floodplain Administrator to administer and
implement this ordinance and other appropriate sections of 44 CFR (National Flood
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:
Assure compliance with the minimum floodplain management requirements
of the State and Federal governing agencies.
Establish, evaluate, disclose and maintain procedures for implementation and
enforcement of this ordinance and compliance with these floodplain
management regulations.
Permit only that development within floodplain management areas which
meets planning considerations that:
a. Meet the minimum criteria and requirements of this ordinance;
Are appropriate in light of the probability of flood damage and the
need to reduce flood losses;
Meet acceptable social and economic use of the land in relation to the
hazards involved, and;
d. Do not increase the danger to human life.
Prohibit nonessential or improper installation of public utilities and public
facilities in floodplain areas.
Prohibit the placement of any nonessential storage, manufacturing, industrial
plants or facilities within a floodplain management area.
17 AGG05228
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 environmentally 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;
Variances have been granted for certain developments or structures;
and
Data is available which shows special flood hazard area and floodplain
management area information for the City.
Prepare and maintain flood warning and emergency preparedness plans which
include:
a. Provision for alternative vehicular access and escape routes; and
Minimum floodproofing and access requirements for schools, hospitals,
nursing homes, orphanages, penal institutions, fire stations, police
stations, communications centers, water and sewage pumping stations,
and other public or quasi-public facilities to enable them to withstand
flood damage, and to facilitate emergency operations.
Enforce 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 management programs.
11.
Require floodplain development permits for all new construction or
development in floodplain management areas of the City.
Assure that conditional approvals are received from FEMA before a
Floodplain Development Permit is issued. Upon written
acknowledgement 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
18 AG005228
assume the cost of any modifications noted by FEMA, as a result of
their technical reviews, to be required for proper completion.
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 FEMA in compliance with the provisions of this ordinance
and the provisions of 44 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 applications for development permits required
by adoption of this ordinance.
15.
Make interpretations as needed to determine the exact location of the
boundaries of floodplain management areas or special flood hazard areas.
16.
Notify the affected communities
Conservation Commission prior to
watercourse, and submit evidence
Emergency Management Agency.
and the Texas Natural Resource
any alteration or relocation of a
of such notification to the Federal
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 Development Permit
A Floodplain Development Permit shall be required for all new construction,
development, and encroachment, including the placement of manufactured homes,
within the floodplain management areas of the City. Application for a Floodplaln
Development Permit shall be presented to the Floodplain Administrator on City
permit forms or facsimiles thereof, which include drawings (to scale) 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 developments on the
floodplain, including impacts on the floodplains, floodways, flood elevations, and
19 AGG~2~
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 shall:
Show the lowest floor 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 minimum lowest floor elevations.
2. Furnish delineations of existing and post-development floodplains.
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. Generally, the following requirements shall be met:
For drainage areas of 0 to 100 square miles the valley storage
reduction shall not exceed 15% for the 100-year flood and 20% for the
standard project flood;
For drainage areas in excess of 100 square miles the valley storage
reduction shall not exceed 0% for the 100-year flood and 5%, for the
standard project flood.
Demonstrate with technical data that the flood carrying capacity within the
altered or relocated portion of any watercourse is maintained.
Demonstrate with technical 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:
Will not increase the water surface elevations of the design base flood
(fully urbanized watershed);
Will not increase the effective FIS base flood (existing condition
watershed) elevations by more than one foot;
Will not increase the base flood water surface elevations of the FIS
regulatory floodway in effect at the time of application for a floodplain
development permit; and
d. Otherwise meets the provisions of Article 5 of this ordinance.
6. Prepare technical data for the Floodplain Administrator's review and
20 AGG05228
submittal to the FEMA.
Affirm that all necessary permits have been obtained from those Federal
(including Section 404 of the Federal Water Pollution Control Act), State, and
other local governmental agencies from which prior approval is required.
SECTION D.
Variances
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
ordinance.
2. Variance Procedures
The Appeal Board shall hear and render judgment on an appeal when
it is alleged there is an error in any requirement, decision or
determination made by the Floodplain Administrator in the
enforcement or administration of this ordinance.
Any person aggrieved by the decision of the Appeal Board may appeal
such decision in the courts of competent jurisdiction.
The Floodplain Administrator shall report any variances, including the
justification for their issuance, to the Federal Emergency Management
Agency upon request.
3. Variance Conditions
Variances shall not be issued within any designated floodway if any
increase in flood levels during the effective FIS base flood discharge
would result.
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.
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 existing structures
constructed below the base flood level for cases of exceptional
hardship, providing the other relevant factors in Subsection 60.6 of 44
CFR 1.1 have been fully considered. Variances for lot sizes greater
than one-half acre contiguous to, and surrounded by, non-complying
lots will only be considered with appropriate technical justification.
Upon consideration of the factors noted, and the intent of this
ordinance, the Appeal Board may attach such conditions to the
granting of variances as it deems necessary to further the purpose and
objectives of this ordinance.
Prerequisites for Granting Variances
Variances shall only be issued upon a determination that the variance
is the minimum necessary, considering the flood hazard, to afford
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
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,
extraordinary public expense, create nuisances, cause fraud on
or victimization of the public, or a conflict with existing local
laws or ordinances.
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 flood elevation, and that the cost of
flood insurance will be commensurate with the increased risk resulting
from the reduced lowest floor elevation.
22 AGG~2~
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 rivefine 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 drawings and technical submittals for work within floodplain management areas
shall be accompanied by certifications by a registered engineer, architect, or surveyor,
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:
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;
Constructed with electrical, heating, ventilation, plumbing, and air
conditioning equipment and 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 (including all replacement systems) shall be designed
to minimize or eliminate infiltration of flood 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 i.e., waste disposal
23 AGG~2~
systems shall not be located within a floodplain management area; and
Design standards of all facilities shall be in accordance with the provisions of
the "Subdivision Ordinance of the City of Coppell."
SECTION B.
Specific Standards
In all floodplain management areas where base flood, design base flood 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 a technical 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,
1985.
1. Residential Construction
The lowest floor (including basement) shall be elevated 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 minimum lowest floor elevations.
In areas of shallow flooding (AO/AH Zones), the lowest floor
(including basement) shall be elevated above the highest adjacent
grade at least as high as the depth number specified in feet on the
FIRM or a minimum of 2 feet, whichever is higher.
A registered professional engineer, architect, or land surveyor shall
submit a certification to the Floodplain Administrator that the
standards of this subsection are satisfied.
2. Nonresidential Construction
Any commercial, industrial or 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 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
24 AGG05228
having the capability of resisting hydrostatic and hydrodynamic loads
and effects of buoyancy.
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 FIRM 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 have the capability of resisting hydrostatic and
hydrodynamic loads and effects of buoyancy.
A registered professional engineer or architect, as applicable, shall
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.
A record of the certification by a registered professional engineer or
architect shall be filed with the Floodplain Administrator.
3. Enclosures
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.
Designs for meeting this requirement must be certified by a registered
professional engineer or architect, or meet or exceed the following
minimum criteria:
(D
A minimum 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 shall be provided.
(2)
The bottom of all openings shall be no higher than one foot
above grade.
(3)
Openings may be equipped with screens, louvers, valves, or
other coverings or devices provided that they permit the
automatic entry and exit of floodwaters.
25 Aooos228
Manufactured Homes
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 minimum of 2 feet above the base flood elevation or to 1
foot above the design base flood, whichever is greater, and be securely
anchored to an adequately anchored foundation system in accordance
with the provisions of Section A of this Article 5.
Manufactured homes shall be in compliance with Section B. 1 of this
Article 5.
Utilities, Bridges, Roadways and other Public Use Facilities
All public utilities including operational pumps, transformers, switching
equipment, and related mechanical and electrical equipment and
facilities for sewer, water, gas, electrical, and communication systems
shall be located and constructed to minimize or eliminate infiltration
and damage during flooding conditions.
All public utility equipment and bridges shall be designed to remain
operable and accessible with a minimum of 2 feet of freeboard above
adjacent FIS base flood elevations or the design base flood, whichever
is greater.
Roadways and parking lots shall be designed to remain usable and
accessible with adequate elevation above the base flood as follows:
(D
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 one foot in the
effective FIS base flood or the design base flood, whichever
elevation is greater, for Collector Streets.
(3)
A minimum pavement flow-line 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.
26 AGG05228
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.
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 required by
Article 4.
6. Floodways
Encroachments 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 encroachments 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.
When a floodway has not been designated, no new construction,
substantial improvements, or other development (including fill) shall
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
more than one foot above the August, 1980, FIS, or above the
most current effective Flood Insurance Study base flood
elevations, whichever is less, at any point within the stream; or,
(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
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
27 AGG05228
sections of this Article 5.
Base flood (including design base flood) elevation data shall be generated for
subdivision proposals and other proposed development including
manufactured home parks and subdivisions if not otherwise provided.
All subdivision proposals including manufactured home parks and subdivisions
shall have adequate drainage provided to reduce exposure to flood hazards.
All subdivision proposals must have the following note placed on the
preliminary and final plat:
"Hoodplain Development Permit Application No. has been
filed with the City of Coppell Floodplain Administrator on
, 19
, Floodplain Administrator,
· Date."
All subdivision proposals shall have the boundaries of the 100-year floodplain
and floodway clearly shown on the preliminary and final plat.
All lots within or adjacent to the 100-year floodplain shall have the lowest
floor elevation for each building site shown on the final plat.
When any part of a subdivision lies within or adjacent to the 100-year
floodplain, a permanent bench mark tied to a designated National Geodetic
Vertical Datum marker shall be established within 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.
When any part of a completed subdivision is within or adjacent to the 100-
year floodplain, the following note must be placed on the final plat:
"The developer, builder, seller, or agent shall inform in
writing, each prospective buyer of subdivision lots or
property located within special flood hazard areas of this
site that such property is in an identified flood hazard
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
28 AGG05228
and a copy of the notice must accompany the application for development
permit.
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 FIRM
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 shall apply to all development within riverine or
lacustrine floodplains of the City:
Design discharges for evaluation of riverine 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:
The "mean annual flood;" defined 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
determined by historical data or regional regression equations of the
State Department of Highways and Public Transportation;
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
than 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 6 acres of
contributing area.
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.
The standard project flood; defined in this ordinance as the flood
which would occur in the event of a 50% PMF as determined by an
evaluation of the probable maximum precipitation as outlined in
Hydrometeorological Reports 51, "Probable Maximum Precipitation
Estimates. United States East of the 105th Meridian" and 52,
"Application of Probable Maximum Precipitation - United States East
of the 105th Meridian."
Alterations of the channel or adjacent floodplain shall not cause the average
channel velocities during the mean annual flood to exceed maximum
permissible velocities upstream or downstream of the project site.
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.
No alterations shall occur to the low-flow channel in park or greenbelt 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.
Flood protection offered by proposed levees shall be designed based on the
standard project flood plus three feet of freeboard.
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.
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.
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.
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.
Design of lakes, ponds, stock tanks, detention, or detention/retention facilities
shall be based on the discharges and other requirements of the Texas Natural
30 AGG05228
Resource Conservation Commission.
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:
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.
A site grading and drainage plan showing proposed cut slopes, fill
slopes, on-site contours, returns to adjacent property contours, existing
contours, and the existing and proposed 100-year flood inundation lines
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.
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.
A narrative describing maintenance requirements to sustain the
assumed Manning'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.
Evidence of water rights and dam safety permits from the Texas
Natural Resource Conservation Commission shall be submitted to the
Floodplain Administrator before water can be impounded in any
lacustrine system.
31 Aoo~2~
ARTICLE 6
Effective Date
This ordinance shall take effect April 15, 1994, after its passage and the publication
of the caption as the law and charter in such cases provide."
DULY,_~tj~y, SED by the City Council of the City of Coppell, Texas, on the
day of J c;/-; , 1994.
APPROVED:
TOM MORTON, MAYOR
ATYEST:
APPROVED AS TO FORM:
CITY ATYORNEY
(RLD/jd 2-28-94)
32 AGG052~