OR 2001-952 New floodplain maps dated 8-23-2001AN ORDINANCE OF THE CITY OF COPPELL
ORDINANCE NO. 2001-952
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 94-639 AND
ALL ORDINANCES IN CONFLICT; PROVIDING A SEVERABILITY CLAUSE;
PROVIDING A SAVINGS CLAUSE; AND PROVIDING AN EFFECTIVE DATE.
BE IT ORDAINED 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.
SECTION B. Statutory Authority
The Legislature of the State of Texas has in the Local Government code 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 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;
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
floodplains in order to reduce the losses incurred
flooding takes place.
manage the riverine
when the inevitable
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.
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;
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;
Minimize damage to public facilities and utilities such as water and gas mains,
electric, telephone and sewer lines, streets and bridges;
Help maintain a stable tax base by providing for secondary uses and development
of floodplain areas (the primary use being conveyance of floodwaters);
Insure that potential buyers are notified that property is in an area of special flood
hazard;
Insure that those who occupy the areas of special flood hazard assume
responsibility for their actions;
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 "development" within the City is subject to the provisions of
this ordinance.
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.
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.
"Administrator" 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 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.
"Appurtenant 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.
"Area 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.
"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, 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 (commonly referred to as the "100-year" flood). 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."
"Baseflood 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," "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 wall" 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."
"Certified Floodplain Manager" A person who has met all requirements established by
the State of Texas to be designated a Certified Floodplain Manager, including passing a
written test and maintaining continuing education credits.
"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 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. A Floodplain Development Permit is required for all development within a
floodplain.
"Development permit" 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 could hinder the passage of water or
otherwise affect flood flows; e.g. fill, buildings, fences and so on. A Floodplain
Development Permit is required for all encroachments.
"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 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."
"Existing structures" See "Existing construction."
"Federal Emergency Management Agency" (FEMA) The Federal agency which
administers the National Flood Insurance Program.
"Flood" or "flooding" 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 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 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", "floodplain land" or "flood-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.
"Floodplain Administrator" The City Engineer of the City of Coppell is the floodplain
administrator for all purposes of this ordinance. The Floodplain Administrator shall be a
"Certified Floodplain Manager".
"Floodplain Development Permit" A permit which must be obtained by any person
before any development begins on land within a floodplain. See "Development" and
"Encroachment".
"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" 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.
"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, 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 riverine 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
floodplain management regulations.
"Floodway" See "Regulatory floodway."
"Floodway encroachment lines" The lines marking the limits of the regulatory floodway
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 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.
"Functionally dependent 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.
"Lacustrine" Of or pertaining 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 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
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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.
"Maximum 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 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" 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."
"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.
"Probable Maximum Flood" (PMF) The most severe flood likely to occur from a
combination of the most critical meteorological and hydrological conditions that are
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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 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.
"Riverine" 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 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).
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"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/or 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
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.
"Usepermit" 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.
"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
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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 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 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 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 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 Dallas County, Texas and
Incorporated Areas," dated August 23, 2001 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.
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SECTION C. Establishment of a 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 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. 94-639 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,
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,
3. Deemed neither to limit nor repeal any other powers granted under State statues.
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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.
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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.
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
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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;
b. 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. This includes the use of detention
basins to limit runoff to predevelopment levels.
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 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
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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 and 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 and the Texas Natural Resource Conservation
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 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. A Floodplain Development Permit will be
required for the initial reclamation of all floodplain lands. Application for a Floodplain
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 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.
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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 developments:
Will not increase the water surface elevations of the design base flood
(fully urbanized watershed);
b. 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.
Prepare technical data for the Floodplain Administrator's review and 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
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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.
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.
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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.
4. 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.
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 riverine 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 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.
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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 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.
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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 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 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 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 shall be
filed with the Floodplain Administrator.
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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 meet or exceed the following minimum criteria:
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.
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.
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Roadways and parking lots shall be designed to remain usable and
accessible with adequate elevation above the base flood as follows:
(1)
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.
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
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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 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:
"Floodplain Development Permit Application No. has been
filed with the City of Coppell Floodplain Administrator on
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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:
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"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 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 Texas
Department of 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.
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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.
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Design of lakes, ponds, stock tanks, detention, or detention/retention facilities
shall be based on the discharges and other requirements of the Texas Natural
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.
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.
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ARTICLE 6
Effective Date
This ordinance shall take effect August 23, 2001, after its passage and the
publication of the caption as the law and charter in such cases provide."
DULY PASSED by the City Council of the City of Coppell, Texas, on the
26th day of June, 2001.
APPROVED:
CANDY SHEEHAN, MAYOR '"---
ATTEST:
LIBBY BALL, CITY SECRETARY
APPROVED AS TO FORM
CITY ATTORNEY-
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