HomeMy WebLinkAboutChapter_58 FloodplainRegulations
Title 18
Chapter 58
FLOODPLAIN REGULATIONS
Sections:
18.58.010 Title
18.58.020 Purpose
18.58.030 Jurisdictional Area
18.58.040 Floodplain Regulation Establishment and Applicability
18.58.050 Abrogation and Greater Responsibility
18.58.060 Floodplain Administrator
18.58.070 Regulation Interpretation
18.58.080 Compliance with Regulations
18.58.090 Flood Hazard Evaluation
18.58.100 Rules for Interpretation of Floodplain District Boundaries
18.58.110 Warning and Disclaimer of Liability
18.58.120 Disclosure Provision
18.58.130 Administration of Regulations
18.58.140 Permit Applications
18.58.150 Emergency Waiver
18.58.160 Review - Variances - Appeals
18.58.170 Floodplain Development - Compliance
18.58.180 Emergency Preparedness - Planning
18.58.190 Applications - Specific Standards
18.58.200 Floodway - Uses Allowed Without Floodplain Permits
18.58.210 Floodway - Uses Requiring Floodplain Permits
18.58.220 Floodway - Permits for Flood Control Works
18.58.230 Floodway - Permits for Water Diversions
18.58.240 Floodway - Prohibited Uses
18.58.250 Floodway Fringe - Uses Allowed Without Permits
18.58.260 Floodway Fringe - Uses Requiring Permits
18.58.270 Floodway Fringe - Prohibited Uses
18.58.280 Floodplain Areas with Flood Elevations and No Delineated Floodway
18.58.290 Shallow Flooding (AD Zones)
18.58.300 Applicability to Unnumbered A Zones
18.58.310 A Zones - Uses Allowed Without Permits
18.58.320 A Zones - Uses Requiring Permits
18.58.330 A Zones - Prohibited Uses
18.58.340 A Zones - Floodplain Boundary Interpretation
18.58.350 Floodproofing Requirements - Certification
18.58.360 Floodproofing Requirements - Conformance
18.58.370 Floodproofing Requirements - Electrical Systems
18.58.380 Floodproofing Requirements - Heating Systems
18.58.390 Floodproofing Requirements - Plumbing Systems
18.58.400 Violation - Notice
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18.58.410 Violation - Penalty
18.58.010 Title
These regulations shall be known and cited as the Bozeman floodplain regulations. This
chapter is in accordance with the authority of the laws of the State of Montana exercised by the
City, and other authority as may be possessed by the City of Bozeman. (Ord. 1645 S 1, 2005)
18.58.020 Purpose
This title has established regulations to prohibit development within floodplains in order to
protect public health and safety, safeguard water quality, provide for wildlife habitat, and
accomplish other public purposes. However, there are certain limited circumstances where
development within the floodplain either currently exists or may be permitted from time to time
to advance a public purpose. This chapter provides standards which must be met in order to
promote the public health, safety, and general welfare, to minimize flood losses in areas subject
to flood hazards, and to promote wise use of the floodplain when those limited circumstances
occur. This chapter has been established with the following purposes intended:
A. To guide development of the 100-year floodplain within the Bozeman city limits
consistent with the enumerated findings by:
1. Establishing zoning regulations coincident with and applicable to those
areas at risk of flooding with special requirements and regulations to
protect the public welfare;
2. Recognizing the right and need of water courses to periodically carry more
than the normal flow of water;
3. Participating in coordinated efforts of federal, state, and local management
activities for 1 DO-year floodplains;
4. Ensuring the regulations and minimum standards adopted, insofar as
possible, balance the greatest public good with the least private injury; and
5. Carry out the provisions of this chapter in a fashion consistent with the
remainder of this title and the public policies set forth in the City's growth
policy consistent with the authority of Title 76, Chapter 5, Part 3, MCA.
B. Specifically, it is the purpose of this chapter to:
1. Restrict or prohibit uses that are dangerous to health, safety, and property
in times of flood or that cause increased flood heights and velocities;
2. Require that uses vulnerable to floods, including public facilities, be
provided with flood protection at the time of initial construction;
3. Identify lands unsuitable for certain development purposes because of
flood hazards;
4. Minimize the need for rescue and relief efforts associated with flooding
undertaken at the expense of the general public;
5. Ensure that potential buyers are notified that property is within a 1 DO-year
floodplain and subject to the provisions of these regulations;
6. Ensure that those who occupy 1 OO-year floodplains assume responsibility
for their actions; and
7. Protect water quality and persons and property located downstream. (Ord.
1645 S 1, 2005)
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18.58.030 Jurisdictional Area
This chapter shall apply to all lands within the boundaries of the City of Bozeman, State of
Montana, shown on the official floodplain maps, including any amendments or revisions, as being
located within a 1 OO-year floodplain district or that may otherwise be identified as lying within a
1 OO-year floodplain through additional floodplain delineation, engineering analysis, topographic
survey, or other objective and factual basis. (Ord. 1645 S 1, 2005)
18.58.040 Floodplain Regulation Establishment and Applicability
These floodplain regulations are hereby established and are applicable in all areas defined
by the base flood elevations and 1 OO-yearfloodplains as delineated in the Flood Insurance Study
or other means specified in S 18.58.030. The basis for the Flood Insurance Study is a scientific
and engineering report entitled "The Flood Insurance Study for the City of Bozeman, Montana,"
dated July 15, 1988, with accompanying Flood Insurance Rate Maps and Flood
Boundary/Floodway Maps. The official floodplain maps, together with the Flood Insurance Study
are on file in the office of the City Floodplain Administrator. The floodplain regulations are hereby
established in all areas subject to flooding. Depiction on the official zoning map of the city is not
required for this district. (Ord. 1645 S 1, 2005)
18.58.050 Abrogation and Greater Responsibility
It is not intended by this chapter to repeal, abrogate, or impair any existing easements,
covenants, deed restrictions, or underlying zoning. However, where this chapter imposes greater
restrictions, the provisions of this chapter shall prevail. (Ord. 1645 S 1, 2005)
18.58.060 Floodplain Administrator
The City Floodplain Administrator has been designated to be the City Engineer. The
responsibilities of this position are outlined in S 18.58.130. (Ord. 1645 S 1, 2005)
18.58.070 Regulation Interpretation
The interpretation and application of the provisions of these regulations shall be considered
minimum requirements and liberally construed in favor of the governing body and not deemed
a limitation or repeal of any other powers granted by state statute or self-government status. (Ord.
1645 S 1,2005)
18.58.080 Compliance with Regulations
No structure or land use shall be located, extended, converted, or structurally altered without
full compliance with the provisions of this title, these specific regulations, and other applicable
regulations. These regulations meet or exceed the minimum floodplain development
requirements as set forth by the Montana Board of Natural Resources and Conservation and the
National Flood Insurance Program. (Ord. 1645 S 1, 2005)
18.58.090 Flood Hazard Evaluation
A. General. Land subject to being flooded by a flood of 1 DO-year frequency as defined
by Title 76, Chapter 5, MCA, or land deemed to be subject to flooding by the City of
Bozeman, shall not be subdivided or developed for building or residential purposes,
or other uses that may increase or aggravate flood hazards to life, health, or
welfare, or that may be prohibited by state or local floodplain or floodway
regulations.
B. Requirement for Study
1. If any portion of a proposed subdivision or other development is:
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a. Within 1,000 horizontal feet and less than 10 vertical feet of a
watercourse draining an area of 25 square miles or more; and
b. No official floodplain or floodway delineation study of the
watercourse has been made; then
c. The subdivider or other developer shall provide a floodplain
analysis report establishing the calculated 1 DO-year frequency
water surface elevations and 1 DO-year floodplain boundaries. The
analysis and report shall be prepared by a licensed professional
engineer qualified in this field of work.
2. If any portion of a proposed subdivision or other development is:
a. Within 1,000 horizontal feet and less than 10 vertical feet of a
watercourse draining an area less than 25 square miles; and
b. No official floodplain or floodway delineation study of the
watercourse has been made; then
c. The subdivider or other developer shall:
(1) Demonstrate to the satisfaction of the City Engineering
Department that the 1 DO-year peak runoff of the
watercourse will not affect the subdivision; or
(2) Delineate the existing and proposed 1 DO-year flood limits
of the stream or streams within 1,000 feet of the
proposed subdivision and specify any mitigation that may
be required to protect the proposed subdivision and
adjacent properties from potential flooding and erosion
damage due to any proposed changes within the
delineated flood limits;
d. The developer's professional engineer, licensed in the State of
Montana, shall provide written certification to the City that the
mapped flood locations and proposed mitigation shall protect
against damage by the 1 OO-year flood.
3. Submission of Report. The report shall be submitted at the time of
preliminary plat or plan application. The report may be submitted, upon the
request of the City Commission or Development Review Committee, to the
Floodplain Management Section, Water Resources Division, and the
Montana Department of Natural Resources and Conservation, for review
and concurrence.
4. Contents of Report. The required report shall include the following
information:
a. Certification. Certification of the report by a registered
professional engineer.
b. Overall Plan View. An overall scaled plan view (project map) with
identified scale for vertical and horizontal distance showing the
following:
(1) Watercourse;
(2) Floodplain boundaries;
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(3) Location of property;
(4) Contours;
(5) Cross sections;
(6) Bridges or other constrictions in the floodplain; and
(7) USGS gauging stations (if any).
c. Benchmark( s). The location and elevation of a temporary
benchmark(s) established within the subdivision and referenced
to mean sea level with appropriate elevation adjustment.
d. Cross Sectional Information
(1) Cross sections shall follow the applicable guidelines
established by the Montana Department of Natural
Resource Conservation. If applicable guidelines are not
available, cross section information shall be as follows:
(a) Cross section elevations and stations should be
determined at points representing significant
breaks in ground slope and at changes in the
hydraulic characteristics of the floodplain (e.g.,
points where ground cover, soil, or rock
conditions change). Elevations must be
reported in NAVD88 or NGVD29 datum.
(b) Each cross section shall cross the entire
floodplain. The cross section alignment should
be perpendicular to the general flow of the
watercourse, the slope of the channel and the
hydraulic characteristics of the reach. A
minimum of four cross sections are required
over the entire reach with at least two cross
sections at the property where the elevations
are desired. Additional cross sections must be
taken at bridges, control structures, or natural
constrictions in topography.
(2) Photogrammetric methods may be used in lieu of cross
sections whenever appropriate and when reviewed and
approved by the City Engineer.
e. Bridges. Descriptions and sketches of all bridges within the
reach, showing unobstructed waterway openings and elevations.
f. Water Surface. Elevations of the water surface determined by
survey as part of each valley cross section.
g. Supporting Documentation. Engineering report of computer
computations, calculations, and assumptions that may include:
(1) Hydrology (research of published hydrology or
calculations showing how hydrology was derived);
(2) Input files (hard copy and on diskette or CD-ROM); and
(3) Output files (hard copy and on diskettes or CD.ROM).
C. Waiver of Requirement. The City Engineer may waive this requirement where the
subdivider contacts the Water Resources Division, of the Montana Department of
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Natural Resources and Conservation, and that agency states in writing that the data
indicate that the proposed subdivision is not in the flood hazard area as defined in
this chapter. (Ord. 16459 1, 2005)
18.58.100 Rules for Interpretation of Floodplain District Boundaries
The boundaries of the 1 DO-year floodway shall be determined by scaling distances on the
official floodplain maps and using the floodway data table contained in the flood insurance study
report. The maps may be used as a guide for determining the 1 OO-year floodplain boundary, but
the exact location of the floodplain boundary shall be determined where the base flood elevation
intersects the natural ground. The floodplain administrator may require an on-site survey and
staking of the floodplain boundary prior to issuance of any permit or any development undertaken
following issuance of a permit. (Ord. 1645 9 1, 2005)
18.58.11 0 Warning and Disclaimer of Liability
This chapter does not imply that areas outside the delineated floodplain boundaries or
permitted land uses will always be totally free from flooding or flood damages. These regulations
shall not create a liability or cause of action against the City or any officer or employee thereof
for flood damages that may result from reliance upon these regulations. (Ord. 1645 S 1, 2005)
18.58.120 Disclosure Provision
All owners of property in an identified 1 OO~year floodplain as indicated on the official
floodplain maps must notify potential buyers or their agents that such property is subject to the
provisions of this chapter. (Ord. 1645 S 1, 2005)
18.58.130 Administration of Regulations
A. As provided in S 18.58.060, the City Floodplain Administrator has been designated
by the City Commission, and has the responsibility of such position as outlined in
this chapter.
B. Section 18.42.100 has established a public policy to avoid development within
floodplains, along with certain exceptions. The administration of these regulations
shall be done in a fashion consistent with both the letter and spirit of that section.
C. The City Floodplain Administrator is appointed with the authority to review floodplain
development permit applications, proposed uses and construction to determine
compliance with these regulations. The City Floodplain Administrator is required to
assure all necessary permits have been received from those governmental
agencies from which approval is required by federal and state law and local codes,
including Section 404 of the Federal Water Pollution Control Act of 1972, 33 use
1334, and under the provisions of the Natural Streambed and Land Preservation
Act.
1. Additional Factors. Floodplain development permits shall be granted or
denied by the City Floodplain Administrator on the basis of whether the
proposed establishment, alteration or substantial improvement of an
artificial obstruction meets the requirements of this chapter and other
requirements of this title. Additional factors that shall be considered for
every permit application are:
a. The danger to life and property due to increased flood heights,
increased flood water velocities or alterations in the pattern of
flood flow caused by encroachments;
b. The danger that materials may be swept onto other lands or
downstream to the injury of others;
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c. The proposed water supply and sanitation systems and the ability
of these systems to prevent disease, contamination, and
unsanitary conditions;
d. The susceptibility of the proposed facility and its contents to flood
damage and the effects of such damage on the individual owner;
e. The importance of the services provided by the facility to the
community;
f. The requirement of the facility for a waterfront location;
g. The availability of alternative locations not subject to flooding for
the proposed use;
h. The compatibility of the proposed use with existing development
and anticipated development in the foreseeable future;
i. The relationship of the proposed use to the growth policy and
floodplain management program for the area;
j. The safety of access to property in times of flooding or for
ordinary and emergency services; and
k. Such other factors as are in harmony with the purposes of this
title, these regulations, the Montana Floodplain and Floodway
Management Act and the National Flood Insurance Program.
D. A floodplain development permit application is considered to have been
automatically granted 60 days after the date of receipt of the application by the City
Floodplain Administrator unless the applicant has been notified that the permit is
denied, conditionally approved, or that additional information pertinent to the permit
review process is required. A floodplain permit shall not act as a waiver or variance
from the other requirements of this title.
E. The City Floodplain Administrator shall adopt such administrative procedures as
may be necessary to efficiently administer the provision of these regulations.
F. The City Floodplain Administrator shall maintain such files and records as may be
necessary to document nonconforming uses, base flood elevations, floodproofing
and elevation certifications, fee receipts, the issuance of permits, agenda, minutes,
records of public meetings, and any other matters related to floodplain management
in the City of Bozeman. Such files and records shall be open for public inspection.
In matters of litigation, the City Attorney may restrict access to specific records.
G. The City Floodplain Administrator may require whatever additional information is
necessary to determine whether the proposed activity meets the requirements of
these regulations. Additional information may include hydraulic calculations
assessing the impact on base flood elevations or velocities, level surveyor
certification by a registered land surveyor, professional engineer, or licensed
architect that the requirements of these regulations are satisfied.
H. Upon receipt of an application for a permit or a variance, the City Floodplain
Administrator shall prepare a notice according to the requirements of Chapter 18.76.
I. Copies of all permits granted must be sent to the Montana Department of Natural
Resources and Conservation in Helena, Montana.
1. In riverine situations, notifications by the City Floodplain Administrator must
be made to adjacent communities, the Floodplain Management Section
(DNRC) and FEMA prior to any alteration or relocation of a stream. The
flood-carrying capacity within the altered or relocated portion of any stream
must be maintained. Erosion control measures shall be incorporated to
ensure stability of altered channels and stream banks. (Ord. 1645 S 1,
2005)
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18.58.140 Permit Applications
A. Activities or uses that require the issuance of a permit, including the expansion or
alteration of such uses, shall not be initiated, established, or undertaken until a
permit has been issued by the City Floodplain Administrator.
B. Permit applicants shall be required to furnish the fOllowing information as deemed
necessary by the City Floodplain Administrator for determining the suitability of the
particular site for the proposed use:
1. Plans in duplicate drawn to scale (including dimensions) showing the
nature, location, and elevation of the lot; existing and proposed structure
locations; fill, storage, or materials site; floodproofing measures; mean sea
level elevation of first floor of proposed structures; and location of the
channel and limits of 1 OO-year floodplain boundary.
2. A plan view of the proposed development indicating external dimensions
of structures; street or road finished grade elevations; well locations;
individual sewage treatment and disposal sites; excavation and/or fill
quantity estimates; and site plan and/or construction plans.
3. Specifications for f1oodproofing, filling, excavating, grading, bank
stabilization, storage of materials, and location of utilities.
4. A professional engineer's or registered architect's design calculations and
certification that the proposed activity has been designed to be in
compliance with these regulations.
5. Certification of floodproofing and/or elevation shall be provided on a
standard form available from the City Floodplain Administrator.
C. To determine that the permit specifications and conditions have been completed,
applicants who have received permits are required to furnish the following at the
time of an on-site conformance inspection:
1. Certification by a registered professional engineer or licensed land
surveyor of the actual mean sea level elevation of the lowest floor
(including basement) of all new, altered, or substantially improved
buildings.
2. If floodproofing techniques were used for buildings, the mean sea level
elevation to which the floodproofing was accomplished must be certified
by a structural engineer or licensed architect in the same manner.
3. Certification shall also be required for artificial obstructions other than
buildings, that the activity was accomplished in accordance with these
regulations and the design plans submitted with the application for the
permit activity. This certification may be waived by the City Floodplain
Administrator if it can be clearly ascertained by a site inspection that the
activity was accomplished in accordance with these regulations.
4. Certification of floodproofing and/or elevation shall be provided on a
standard form available from the City Floodplain Administrator. (Ord. 1645
S 1 , 2005)
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18.58.150 Emergency Waiver
A. Emergency repair and replacement of severely damaged public transportation
facilities, public water and sewer facilities, public utility electricity and natural gas
distribution facilities, and flood control works may be authorized. Floodplain
development permit requirements may be waived if:
1. Upon notification and prior to emergency repair and/or replacement, the
City Floodplain Administrator determines that an emergency condition
exists warranting immediate action; and
2. The City Floodplain Administrator agrees upon the nature and type of
proposed emergency repair and/or replacement.
S. Authorization to undertake emergency repair and replacement work may be given
verbally if the City Floodplain Administrator feels that such a written authorization
would unduly delay the emergency works. Such verbal authorization must be
followed by a written authorization describing the emergency condition, and the type
of emergency work agreed upon and stating that a verbal authorization had been
previously given. (Ord. 16459 1, 200S)
18.58.160 Review - Variances - Appeals
Appeals and variances from this chapter may be taken as set forth in Chapter 18.66. The City
Floodplain Administrator shall maintain records of the variance notification and actions, including
justification for their issuance and forward copies of all variance actions to the Montana
Department of Natural Resources and Conservation and the Federal Emergency Management
Agency. (Ord. 16459 1,2005)
18.58.170 Floodplain Development - Compliance
Any use, arrangement, or construction not in compliance as authorized by permit, shall be
deemed a violation of this chapter and punishable as provided in Chapter 18.64. An applicant
is required to submit certification by a registered professional engineer, architect, land surveyor
or other qualified person designated by the City Floodplain Administrator that finished fill and
lowest building floor elevations, flood proofing, hydraulic design, or other flood protection
measures were accomplished in compliance with these regulations. (Ord. 1645 9 1, 200S)
18.58.180 Emergency Preparedness - Planning
In formulating community development goals, the community shall consider the development
of a plan for evacuating users of all development located within flood prone areas. This plan
should be developed, filed with, and approved by appropriate community emergency
management authorities. (Ord. 16459 1, 2005)
18.58.190 Applications - Specific Standards
The minimum floodplain development standards listed in this chapter apply to the floodway
and floodway fringe portions of the 1 DO-year floodplain as delineated on the flood hazard area
maps or other flood hazard areas as may be determined by 9 18.58.040. (Ord. 1645 9 1, 2005)
18.58.200 Floodway - Uses Allowed Without Floodplain Permits
When a site specific exemption or relaxation of the standards of 9 18.42.100 allow utilization
of a portion of the floodplain, the following uses shall be allowed without a permit within the
floodway, provided that such uses conform to the provisions of 9918.58.350 through 18.S8.390;
are not prohibited by any other ordinance, resolution, or statute; and do not require fill,
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excavation, permanent storage of materials, or equipment or structures other than portable
structures:
A. Agricultural uses;
B. Accessory uses such as loading and parking areas associated with industrial and
commercial facilities;
C. Private and public recreational uses such as golf courses, driving ranges, archery
ranges, picnic grounds, boat-launching ramps, parks, wildlife management and
natural areas, fish hatcheries, fishing areas, and hiking or horseback riding trails;
D. Residential uses such as lawns, gardens, parking areas, and play areas;
E. Irrigation and livestock supply wells, provided that they are located at least SOD feet
from domestic water supply wells; and
F. Fences, except permanent fences crossing channels. (Ord. 1645 9 1, 2005)
18.58.210 Floodway - Uses Requiring Floodplain Permits
When a site specific exemption or relaxation of the standards of 9 18.42.100 allow utilization
of a portion of the floodplain, the following artificial obstructions may be permitted in the floodway
subject to the issuance of a permit by the City Floodplain Administrator:
A. Excavation of material from pits and pools provided that:
1. A buffer strip of undisturbed land is left between the edge of the channel
and the edge of the excavation. This buffer strip must be of sufficient width
to prevent flood flows from channeling into the excavation;
2. The excavation meets all applicable laws and regulations of other local and
state agencies; and
3. Excavated material is disposed of or stockpiled outside the floodway;
B. Railroad, highway, and street stream crossings provided the crossings are designed
to offer minimal obstruction to flood flow. Stream crossings shall not increase the
elevation of the 1 DO-year flood more than one-half foot nor cause a significant
increase in flood velocities;
C. Limited filling for highway, street, and railroad embankments not associated with
stream crossings, provided that:
1. Reasonable alternate transportation routes outside the designated
floodway are not available; and
2. Such floodway encroachment is located as far from the stream channel as
possible and shall not result in a cumulative increase in base flood
elevations, after allowable encroachments into the floodway fringe,
exceeding one-half foot;
D. Buried or suspended utility transmission lines, provided that:
1. Suspended utility transmission lines are designed so the lowest point of the
suspended line is at least 6 feet higher than the base flood elevation;
2. Towers and other appurtenant structures are designed and placed to
withstand and minimally obstruct flood flows; and
3. Utility transmission lines carrying toxic or flammable materials are buried
to a depth of at least twice the calculated maximum depth of scour for a
1 DO-year flood. The maximum depth of scour shall be determined by
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hydraulic engineering methods acceptable to the City Floodplain
Administrator;
E. Storage of materials and equipment, provided that:
1. The material or equipment is not subject to major damage by flooding and
is properly anchored to prevent floatation or downstream movement; or
2. The material or equipment is readily movable within the limited time
available after flood warning. Storage of flammable, toxic, hazardous, or
explosive materials shall not be permitted;
F. Domestic water supply wells, provided that:
1. They are driven or drilled wells located on ground higher than the
surrounding ground to assure positive drainage from the well;
2. Well casings are watertight to a distance of at least 25 feet below the
ground surface;
3. Water supply and electrical lines have a watertight seal where the lines
enter the casing;
4. All pumps, electrical lines, and equipment are either submersible or
adequately flood-proofed; and
5. Check valves are installed on main water lines at wells and at all building
entry locations;
G. Substantial improvements to any structure provided that the provisions of
Subsections C, D, or E of 9 18.58.260 are met. In the floodway, the structure must
be flood proofed or elevated on a permanent foundation rather than on fill; and
H. All other artificial obstructions, substantial improvements or nonconforming uses not
specifically listed or prohibited by these regulations. (Ord. 1645 9 1, 2005)
18.58.220 Floodway - Permits for Flood Control Works
It is desired that flood control be primarily accomplished by on-site stormwater management,
protection of bank stabilizing vegetation, preserving an unobstructed floodplain, and keeping
development away from areas prone to flooding. In the event that adequate flood control can not
be achieved by these methods, flood control works shall be allowed within floodways subject to
the issuance of a permit by the City Floodplain Administrator with the following conditions:
A. Levees and floodwalls are permitted if:
1. The proposed levee or f100dwall is designed and construed to safely
convey a 1 OO-year flood; and
2. The cumulative effect of the levee or floodwall combined with allowable
floodway fringe encroachments does not increase the unobstructed base
flood elevation more than one-half foot. The City Floodplain Administrator
may establish either a lower or higher permissible increase in the base
flood elevation for individual levee projects only with concurrence from the
Montana Department of Natural Resources and Conservation and the
Federal Emergency Management Agency based upon consideration of the
following criteria:
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a. The estimated cumulative effect of any anticipated future
permissible uses; and
b. The type and amount of existing flood~prone development in the
affected area;
3. The proposed levee or floodwall, except those to protect agricultural land,
is constructed at least 3 feet higher than the base flood elevation;
B. Bank stabilization methods provided that:
1. When selecting a bank stabilization method, best management practices
consistent with the intent of this title shall be used;
2. The bank stabilization method is designed to withstand a 1 OO-year flood;
3. The bank stabilization method does not increase the base flood elevation;
and
4. The bank stabilization method will not increase erosion upstream,
downstream or adjacent to the stabilization site;
C. Channelization projects if they do not significantly increase the magnitude, velocity
or base flood elevation in the proximity of the project;
D. Dams provided that:
1. They are designed and constructed in accordance with the Montana Dam
Safety Act and applicable safety standards; and
2. They will not increase flood hazards downstream, either through
operational procedures or improper hydraulic design. (Ord. 16459 1,2005)
18.58.230 Floodway - Permits for Water Diversions
Permits for the establishment of a water diversion or change in place of diversion shall not
be issued if, in the judgment of the City Floodplain Administrator:
A. The proposed diversion will significantly increase the upstream base flood elevation
to the detriment of neighboring property;
B. The proposed diversion is not designed and constructed to minimize potential
erosion from a 1 OO-year flood; and
C. Any permanent diversion structure crossing the full width of the stream channel is
not designed and constructed to safely withstand a 1 OO~year flood. (Ord. 16459 1,
2005)
18.58.240 Floodway - Prohibited Uses
The following artificial obstructions and nonconforming uses are prohibited within the
floodway:
A. New construction of any residential, commercial or industrial structure including
manufactured homes;
B. Encroachments including fill, new construction, alterations, substantial
improvements, and other development within the adopted regulatory floodway that
would result in erosion of the embankment, obstruction of the natural flow of waters
or increase in flood levels within the community during the occurrence of the
1 DO-year flood;
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C. The construction or permanent storage of an object subject to floatation or
movement during flooding;
D. Solid and hazardous waste disposal, sewage treatment, and sewage disposal
systems;
E. Storage of toxic, flammable, hazardous, or explosive materials; and
F. Alterations of structures unless it can be shown the alteration will not raise flood
heights. (Ord. 1645 9 1, 200S)
18.58.250 Floodway Fringe - Uses Allowed Without Permits
All uses allowed in the floodway, according to the provisions of 9 18.58.210 of these
regulations, shall also be allowed without a permit in the floodway fringe. (Ord. 1645 9 1, 200S)
18.58.260 Floodway Fringe - Uses Requiring Permits
When a site specific exemption or relaxation of the standards of 918.42.100 allows utilization
of a portion of the floodplain, the uses allowed in the floodway subject to the issuance of a
permit, according to the provisions of 9918.58.220 through 18.58.240, shall also be allowed by
permit within the f100dway fringe. In addition, new construction, substantial improvements, and
alterations to structures are allowed by permit. This includes but is not limited to residential,
commercial, and industrial construction and suitable fill to be allowed by permit from the City
Floodplain Administrator, subject to the following conditions:
A. Such structures or fill must not be prohibited by any other statute, regulation,
ordinance, or resolution;
B. Such structures or fill must be compatible with local growth policies;
C. The new construction, alterations, and substantial improvements of residential
structures including manufactured homes must be constructed on suitable fill such
that the lowest floor elevation (including basement) is 2 feet or more above the base
flood elevation. The suitable fill shall be at an elevation no lower than the base
flood elevation and shall extend for at least 1S feet, at that elevation, beyond the
structure(s) in all directions;
D. The new construction, alteration and substantial improvement of commercial and
industrial structures can be constructed on suitable fill as specified in Subsection C
of this section. If not constructed on fill, commercial and industrial structures must
be adequately flood proofed to an elevation no lower than 2 feet above the base
flood elevation. Floodproofing must be certified by a registered professional
engineer or architect that the floodproofing methods are adequate to withstand the
flood depths, hydrodynamic, and hydrostatic pressures, velocities, impact, buoyancy
and uplift forces associated with the 1 DO-year flood;
1. If the structure is designed to allow internal flooding of areas below the
lowest floor, use of this space shall be limited to parking, loading areas,
building access, and storage of equipment or materials not appreciably
affected by flood waters. The floors and walls shall be designed and
constructed of materials resistant to flooding to an elevation no lower than
2 feet above the base flood elevation. Walls shall be designed to
automatically equalize hydrostatic forces by allowing for entry and exit of
floodwaters. Openings may be equipped with screens, louvers, valves,
other coverings, or devices which permit the automatic entry and exit of
floodwaters;
2. Structures whose lowest floors are used for a purpose other than parking,
loading, or storage of materials resistant to flooding shall be f1oodproofed
to an elevation no lower than 2 feet above the base flood elevation.
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Floodproofing shall include impermeable membranes or materials for floors
and walls and watertight enclosures for all windows, doors, and other
openings. These structures shall also be designed to withstand the
hydrostatic, hydrodynamic, and buoyancy effects of a 1 OO.year flood; and
3. Floodproofing of electrical, heating, and plumbing systems shall be
accomplished in accordance with SS 18.58.350 through 18.58.390;
E. All manufactured homes placed in the floodway fringe must have the chassis
securely anchored to a foundation system that will resist floatation, collapse or
lateral movement. Methods of anchoring may include, but are not limited to,
over.the-top or frame ties to ground anchors. The following conditions also apply:
1. When a manufactured home is altered, replaced because of substantial
damage as a result of a flood, or replaced on an individual site, the lowest
floor must be elevated 2 feet above the base flood elevation. The home
can be elevated on fill or raised on a permanent foundation of reinforced
concrete, reinforced mortared block, reinforced piers, or other foundation
elements of at least equivalent strength.
2. Replacement or substantial improvement of manufactured homes in an
existing manufactured home community or subdivision must be raised on
a permanent foundation. The lowest floor must be at least 36 inches
above the ground or raised 2 feet above the base flood elevation,
whichever is less. The foundation must consist of reinforced concrete,
reinforced mortared block, reinforced piers, or other foundation elements
of at least equivalent strength.
3. Manufactured homes proposed for use as commercial or industrial
structures must be elevated and anchored, rather than flood proofed;
F. Fill material placed in the floodway fringe must be stable, compacted, well graded,
pervious, generally unaffected by water and frost, devoid of trash or similar foreign
matter, devoid of tree stumps or other organic material, and appropriate for the
purpose of supporting the intended use and/or permanent structure;
G. Roads, streets, highways, and rail lines shall be designed to minimize increase in
flood heights. Where failure or interruption of transportation facilities would result
in danger to the public health or safety, the facility shall be located 2 feet above the
base flood elevation; and
H. Agricultural structures that have a low damage potential, such as sheds, barns,
shelters, and hay or grain storage structures must be adequately anchored to
prevent floatation or collapse and all electrical facilities shall be placed above the
base flood elevation;
1. Recreational vehicles, if they are on the site for more than 180 consecutive
days or are not ready for highway use, must meet the elevating
requirements of Subsection C of this section. (Ord. 1645 S 1, 2005)
18.58.270 Floodway Fringe - Prohibited Uses
The following artificial obstructions and nonconforming uses are prohibited within the
floodway fringe:
A. Solid and hazardous waste disposal; and
B. Storage of highly toxic, flammable, hazardous, or explosive materials. Storage of
petroleum products may be allowed by permit if stored on compacted fill at least 2
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feet above the base flood elevation and anchored to a permanent foundation to
prevent downstream movement. (Ord. 1645 9 1, 2005)
18.58.280 Floodplain Areas with Flood Elevations and No Delineated Floodway
A. A development proposed for a 1 DO-year floodplain, where water surface elevations
are available but no floodway is delineated, may not significantly increase flood
velocities or depths or generally alter patterns of flood flow. The provisions of 99
18.58.250 through 18.58.270 shall apply to these areas. The City Floodplain
Administrator may require a permit applicant to furnish additional hydraulic data
before acting on a permit application for such a floodplain. The data may include,
but are not limited to, any of the following:
1. A hydraulic study documenting probable effect on upstream, downstream,
or adjacent property owners caused by the proposed development; or
2. The calculated increase in the 1 OO-year flood water surface profile caused
by the proposed development.
S. Permits for such proposed development may be modified or denied if the additional
information shows that the proposed use would cause an additional flood hazard to
adjacent property or significantly increase flood heights. A significant increase in
flood height is one-half foot unless existing or anticipated development in the area
dictates a lesser amount of allowable increase. (Ord. 16459 1,2005)
18.58.290 Shallow Flooding (AO Zones)
A. Shallow flooding areas are delineated as AO zone floodplains on the Flood
Insurance Rate Maps. The provisions of 9 18.58.260 shall apply to any AO zone
floodplains. The depth of the 1 DO-year flood is indicated as the depth number on
the Flood Insurance Rate Maps. The 1 OO-year flood depth shall be referenced to
the highest adjacent grade or stream flow line in determining which fill or
flood proofing heights to use in applying the provisions of Subsections C and D of
9 18.58.260. In the absence of depth or elevation information, a minimum 2-foot
flood depth shall be used.
B. Floodplain Boundary Interpretation. The City Floodplain Administrator shall make
interpretations where needed as to the exact location of an AO zone floodplain
boundary when there is a conflict between a mapped boundary and actual field
conditions. (Ord. 1645 9 1, 2005)
18.58.300 Applicability to Unnumbered A Zones
The minimum floodplain development standards listed in this section apply to the 1 DO-year
floodplains delineated by approximate methods and identified as unnumbered A zones on the
Flood Insurance Rate Maps. (Ord. 1645 9 1, 2005)
18.58.310 A Zones - Uses Allowed Without Permits
All uses allowed in a floodway, according to the provisions of 9 18.58.210 shall also be
allowed without a permit in unnumbered A zone floodplains. (Ord. 1645 9 1, 2005)
18.58.320 A zones - Uses Requiring Permits
All uses allowed in the floodway and floodway fringe subject to the issuance of a permit
according to the provisions of 9 18.58.260 shall require permits from the City Floodplain
Administrator for unnumbered A zone floodplains. Also, the provisions of 9 18.58.260 apply to
the A zone floodplains with no floodway delineated or water surface profile computed. Since
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there are no 1 DO-year flood water surface profiles computed for A zone floodplains, the following
conditions also apply:
A. Elevation data on the 100-year flood shall be provided for subdivision proposals
according to the definitions and rules of the Montana Sanitation in Subdivisions Act,
Title 76, Chapter 4, Part 1, MCA, and the rules adopted by Department of
Environmental Quality under this Act. These data shall be used in applying
Subsections C, D, and E of 9 18.58.270. Subdivision proposals shall also provide
for adequate drainage to minimize potential flood hazards.
B. The City Floodplain Administrator may obtain, review, and reasonably use any base
flood elevation and floodway data available from federal, state, or other sources,
until such data have been provided by FEMA, to enforce Subsections C and D of
S 18.58.270.
C. The City Floodplain Administrator may use historical flood elevations to determine
suitable fill or floodproofing elevations as required by Subsections C and D of 9
18.58.270.
D. If historical flood evidence is not available, then the City Floodplain Administrator
shall determine, from a field review at the proposed development site, an
appropriate fill or floodproofing elevation to use in applying Subsections C and D of
9 18.58.270. In the absence of depth or elevation information, a minimum 2 foot
flood depth shall be used.
E. Proposed structures must be anchored to prevent floatation or collapse and must
be located as far from stream channels as practicable. (Ord. 16459 1, 2005)
18.58.330 A Zones - Prohibited Uses
Those uses prohibited in the floodway fringe, in accordance with 9 18.58.270 shall also be
prohibited within the A zone floodplain boundaries. (Ord. 1645 9 1, 2005)
18.58.340 A Zones - Floodplain Boundary Interpretation
The City Floodplain Administrator shall make interpretations where needed as to the exact
location of the unnumbered A zone floodplain boundary when there is a conflict between a
mapped boundary and actual field conditions. (Ord. 1645 9 1, 2005)
18.58.350 Floodproofing requirements - Certification
If the following floodproofing requirements are to be applied to a proposed structure, as
stipulated by the City Floodplain Administrator in accordance with these regulations, the methods
used must be certified as adequate by a registered professional engineer or architect. (Ord. 1645
9 1, 2005)
18.58.360 Floodproofing Requirements - Conformance
Permitted floodproof systems shall conform to the conditions listed in 99 18.58.370 through
18.58.390 and the floodproofing standards listed in Subsection D of 9 18.58.260 for commercial
and industrial structures. (Ord. 1645 9 1, 2005)
18.58.370 Floodproofing Requirements - Electrical Systems
A. All incoming power service equipment, including all metering equipment, control
centers, transformers, distribution and lighting panels, and all other stationary
equipment must be located at least 2 feet above the base flood elevation;
B. Portable or movable electrical equipment may be placed below the base flood
elevation, if the equipment can be disconnected by a single submersible
plug-and-socket assembly;
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C. The main power service line shall have automatic or manually operated electrical
disconnect equipment located at an accessible location outside the 100-year
floodplain and above the base flood elevation; and
D. All electrical wiring systems installed at or below the elevation of the 1 OO.year flood
shall be suitable for continuous submergence and may not contain fibrous
components. (Ord. 1645 S 1, 200S)
18.58.380 Floodproofing Requirements - Heating Systems
A. Float operated automatic control valves must be installed in gas furnace supply
lines so that the fuel supply is automatically shut off when flood waters reach the
floor level where the furnace is located;
B. Manually operated gate valves must be installed in gas supply lines. The gate
valves must be operable from a location above the elevation of the 1 OO-year flood;
and
C. Electric heating systems must be installed in accordance with the provisions of
International Building Code and any other applicable regulations. (Ord. 1645 S 1,
2005)
18.58.390 Floodproofing Requirements - Plumbing Systems
A. Sewer lines, except those to be buried and sealed in vaults, must have check valves
installed to prevent sewage backup into permitted structures; and
B. All toilet stools, sinks, urinals, and drains must be located so the lowest point of
possible water entry is at least 2 feet above the elevation of the 100.year flood.
(Ord. 1645 S 1, 2005)
18.58.400 Violation - Notice
The City Floodplain Administrator shall bring any violation of this chapter to the attention of
the local governing body, its legal council and the Montana Department of Natural Resources and
Conservation. (Ord. 1645 S 1, 2005)
18.58.410 Violation - Penalty
Violation of the provisions of this chapter or failure to comply with any of the requirements,
including permit approval prior to development of floodprone lands, and conditions and
safeguards established shall be subject to the provisions of Chapter 18.64. (Ord. 1645 S 1, 200S)
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