(A) Authority. The Legislature of the State of Iowa has, in I.C.A. Chapter 414, as amended, delegated the power to cities to enact zoning regulations to secure safety from floods and to promote health and the general welfare.
(B) Flooding. The flood hazard areas of the city are subject to periodic inundation which can 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 health, safety and general welfare of the community. These losses, hazards, and related adverse effects are caused by:
(1) The cumulative effect of floodplain construction on flood flows, which causes increases in flood heights and flood water velocities; and
(2) The occupancy of flood hazard areas by uses vulnerable to flood damages which create hazardous conditions as a result of being inadequately elevated or otherwise protected from flooding.
(C) Methodology. This Zoning Ordinance relies upon engineering methodology for analyzing flood hazards which is consistent with the standards established by the Iowa Department of Natural Resources.
(D) Intent. The provisions of this section are designed to:
(1) Reserve sufficient floodplain area for the conveyance of flood flows so that flood heights and velocities will not be increased substantially;
(2) Restrict or prohibit uses that are dangerous to health, safety, or property in times of flood or which cause excessive increases in flood heights or velocities;
(3) Require that uses vulnerable to floods, including public utilities which serve such uses, be protected against flood damage at the time of initial construction;
(4) Protect individuals from buying lands which are unsuited for intended purposes because of flood hazard; and
(5) Assure that eligibility is maintained for property owners in the community to purchase flood insurance through the National Flood Insurance Program.
(E) Applicability. The regulations of the Flood Hazard Districts shall apply to all lands within the jurisdiction of the city shown on the Floodway Boundary and Floodway Map to be within the 100-year flood boundaries.
(F) Establishment of Official Floodplain Zoning Map. The Flood Boundary and Floodway Maps prepared as part of the "Flood Insurance Study for the City of Marshalltown, Iowa", dated April 17, 1984, are hereby adopted by reference and declared to be the Official Floodplain Zoning Map. The flood profiles and all explanatory material provided with the "Flood Insurance Study" and the Flood Insurance Rate Maps are also declared to be a part of this section.
(G) Rules for Flood Hazard Overlay Districts boundaries interpretation. The boundaries of the Flood Hazard Overlay Districts shall be determined by scaling distances on the Official Floodplain Map. Where interpretation is needed as to the exact location of the boundaries of the district as shown on the Official Zoning Map, the Floodplain Administrator or Engineering Department shall make the necessary interpretation. The person contesting the location of the overlay boundary shall be given a reasonable opportunity to present their case and submit technical evidence.
(H) Compliance. No structure or land shall be used and no structure shall be located, extended, converted, or structurally altered without full compliance with the terms of this Zoning Ordinance and other applicable regulations which apply to uses within the jurisdiction of this Zoning Ordinance.
(I) Abrogation and greater restrictions. It is not intended by this section to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this section imposes greater restrictions, the provisions of this section shall prevail. All other ordinances inconsistent with this section are hereby repealed to the extent of the inconsistency only.
(J) Interpretation. In their interpretation and application, the provisions of this section shall be held to be minimum requirements and shall be literally construed in favor of the governing body and shall not be deemed a limitation or repeal of any other powers granted by state statutes.
(K) Warning and disclaimer of liability. The degree of flood protection required by this section is considered reasonable for regulatory purposes and is based on engineering and scientific methods of study. Larger floods may occur on rare occasions. Flood heights may be increased by human-made or natural causes, such as ice jams and bridge openings restricted by debris. This section does not imply that areas outside the floodplain districts or land uses permitted within such districts will be free from flooding or flood damages. This regulation shall not create liability on the part of the City of Marshalltown for any flood damages that result from reliance on this section or any administrative decision resulting from this section.
(L) Severability. If any section, clause, provision, or portion of this section is adjudged unconstitutional or invalid by a court of competent jurisdiction, the remainder of this section shall not be affected by such judgement.
(M) Flood Hazard Overlay Districts established. The floodplain areas within the jurisdiction of this Zoning Ordinance are divided into the following subdistricts:
(1) Floodway Overlay District. The Floodway Overlay District shall be consistent with the boundaries of the floodway as shown on the Official Floodplain Map.
(2) Floodway Fringe Overlay District. The Floodway Fringe Overlay District shall be those areas shown as floodway fringe on the Official Floodplain Zoning Map designated as Zones A2 - A4, A6, and A8.
(3) General Floodplain Overlay District. The General Floodplain Overlay District shall be those areas shown on the Official Floodplain Zoning Map as being within the approximate 100-year flood boundary designated as Zone A.
(N) Floodway Overlay District.
(1) Permitted uses. All uses within the Floodway Overlay District shall be permitted to the extent that they are not prohibited by any other ordinance (or underlying zoning district), and provided they meet applicable performance standards of the Floodway Overlay District.
(2) Performance standards. All floodway subdistrict uses allowed as a permitted or special use shall meet the following standards:
(a) No use shall be permitted in the floodway subdistrict that would result in any increase in the base flood elevation. Consideration of the effects of any development on flood levels shall be based upon the assumption that an equal degree of development would be allowed for similarly situated lands.
(b) All uses within the floodway subdistrict shall:
1. Be consistent with the need to minimize flood damage;
2. Use construction methods and practices that will minimize flood damage; and
3. Use construction materials and utility equipment that are resistant to flood damage. No use shall affect the capacity or conveyance of the channel or floodway or any tributary to the main stream, drainage ditch, swale, or any other drainage facility or system.
(c) Structures, buildings, and sanitary and utility systems, if permitted, shall meet the applicable performance standards of the floodway fringe subdistrict, and shall be constructed or aligned to present the minimum possible resistance to flood flows.
(d) If permitted, buildings, shall have a low flood damage potential, and shall not be for human habitation, and shall adhere to all applicable provisions of this section.
(e) Storage of equipment or materials that are buoyant, flammable, explosive, or injurious to human, animal, or plant life is prohibited. Storage of other material may be allowed if readily removable from the floodway subdistrict within the time available after flood warning.
(f) Watercourse alterations or relocations (channel changes and modifications) must be designed to maintain the flood carrying capacity within the altered or relocated portion. In addition, such alterations or relocations must be approved by the Iowa Department of Natural Resources, the United States Corps of Engineers, and other applicable agencies.
(g) Any fill allowed in the floodway must be permitted by the Iowa Department of Natural Resources and shall be shown to have some beneficial purpose and shall be limited to the minimum amount necessary.
(h) Subject to all applicable permits of regulating agencies, pipeline river or stream crossings shall be buried in the streambed and banks or otherwise sufficiently stabilized and protected to prevent rupture due to channel degradation and meandering or due to the action of flood flows.
(O) Floodway Fringe Overlay District.
(1) Permitted uses. All uses within the floodway fringe subdistrict shall be permitted to the extent that they are not prohibited by any other ordinance or underlying zoning district, and provided they meet applicable performance standards of the floodway fringe subdistrict.
(2) Performance standards. All uses must be consistent with the need to minimize flood damage and shall meet the following applicable performance standards.
(a) All structures. All structures shall:
1. Be adequately anchored to prevent flotation, collapse, or lateral movement of the structure;
2. Be constructed with materials and utility equipment resistant to flood damage; and
3. Be constructed by methods and practices that minimize flood damage.
(b) Residential buildings. All new or substantially improved residential structures shall have the lowest floor, including basements, elevated a minimum of one foot above the 100-year flood level. Construction shall be upon compacted fill which shall, at all points, be no lower than one foot above the 100-year flood level and extend at such elevation at least 18 feet beyond the limits of any structure erected thereon. Alternate methods of elevating (such as piers) may be allowed, subject to favorable consideration by the Floodplain Administrator, where existing topography, street grades, or other factors preclude elevating by fill. In such cases, the methods used must be adequate to support the structure as well as withstand the various forces and hazards associated with flooding. All new residential buildings shall be provided with a means of access that will be passable by wheeled vehicles during the 100-year flood.
(c) Non-residential buildings. All new or substantially improved non-residential buildings shall have the first floor (including basement) elevated a minimum of one foot above the 100-year flood level, or together with attendant utility and sanitary systems, be flood-proofed to such a level. When floodproofing is utilized, a professional engineer registered in the state shall certify that the flood-proofing methods used are adequate to withstand the flood depths, pressures, velocities, impact and uplift forces and other factors associated with the 100-year flood, and that the structure, below the 100-year flood level, is water-tight with walls substantially impermeable to the passage of water. A record of the certification indicating the specific elevation (in relation to National Geodetic Vertical Datum) to which any structures are floodproofed shall be maintained by the Floodplain Administrator.
(d) New and improved structures. All new and substantially improved structures:
1. Fully enclosed areas below the "lowest floor" (not including basements) 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 flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer or meet or exceed the following minimum criteria:
A. 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.
B. The bottom of all openings shall be no higher than one foot above grade.
C. Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided that, they permit the automatic entry and exit of flood waters.
2. New and substantially improved structures must be designed (or modified) and adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
3. New and substantially improved structures must be 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.
(e) Factory-built homes.
1. Factory-built homes including those placed in existing factory-built home parks or subdivisions shall be anchored to resist flotation, collapse, or lateral movement.
2. Factory-built homes including those placed in existing factory-built home parks or subdivisions shall be elevated on a permanent foundation such that the lowest floor of the structure is a minimum of one foot above the 100-year flood level.
(f) Utility and sanitary systems.
1. All new and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system as well as the discharge of effluent into flood waters. Wastewater treatment facilities shall be provided with a level of flood protection equal to or greater than one foot above the 100-year flood elevation.
2. On-site waste disposal systems shall be located or designed to avoid impairment to the system or contamination from the system during flooding.
3. New or replacement water supply systems and water supply treatment facilities shall be designed in accordance with Iowa DNR requirements and protected to a level equal to or greater than one foot above the 100-year flood elevation.
4. Utilities such as gas and electrical systems shall be located and constructed to minimize or eliminate flood damage to the system and the risk associated with such flood damaged or impaired systems.
(g) Flammable materials and the like. Storage of materials and equipment that are flammable, explosive or injurious to human, animal or plant life is prohibited unless elevated a minimum of one foot above the 100-year flood level. Other material and equipment must either be similarly elevated, or:
1. Not be subject to major flood damage and be anchored to prevent movement due to flood waters; or
2. Be readily removable from the area within the time available after flood warning.
(h) Flood control structural works. Private flood control structural works such as levees, private flood walls and the like shall provide, at a minimum, protection from a 100-year flood with a minimum of three feet of design freeboard and shall provide for adequate interior drainage. In addition, private structural flood control works shall be approved by the state’s Department of Natural Resources.
(i) Affect. No use shall affect the capacity or conveyance of the channel or floodway of any tributary to the main stream, drainage ditch or other drainage facility or system.
(j) Subdivisions. Subdivisions (including manufactured home parks and subdivisions) shall be consistent with the need to minimize flood damages and shall have adequate drainage provided to reduce exposure to flood damage. Development associated with subdivision proposals shall meet the applicable performance standards. Subdivision proposals shall meet city standard specifications in regards to flood protection and storm water conveyance.
(k) Detached structures. The exemption of detached garages, sheds and similar structures from the 100-year flood elevation requirements may result in increased premium rates for insurance coverage of the structure and contents, however, said detached garages, sheds and similar accessory type structures are exempt from the 100-year flood elevation requirements when:
1. The structure shall not be used for human habitation;
2. The structure shall be designed to have low flood damage potential;
3. The structure shall be constructed and placed on the building site so as to offer minimum resistance to the flow of flood waters;
4. Structures shall be firmly anchored to prevent flotation which may result in damage to other structures; and
5. The structure’s service facilities such as electrical and heating equipment shall be elevated or floodproofed to at least one foot above the 100-year flood level.
(l) Recreational vehicles. Recreation vehicles placed on sites within this district shall either:
1. Be on the site for fewer than 180 consecutive days;
2. Be fully licensed and ready for highway use; or
3. Meet the requirements the section.
(P) General Floodplain Overlay District.
(1) Permitted uses. The following uses shall be permitted within the general flood plain subdistrict to the extent they are not prohibited by any other ordinance or underlying zoning district; and provided they meet the applicable performance standards of the General Floodplain District:
(a) Any uses which involve placement of structures, factory-built homes, fill or other obstructions, storage of materials or equipment, excavation or alteration of a watercourse may be allowed only upon approval by the Floodplain Administrator.
(b) All such uses shall be reviewed by the Iowa Department of Natural Resources to determine: whether the land involved is either wholly or partly within the floodway or floodway fringe and the base flood elevation. The applicant shall be responsible for providing the Iowa Department of Natural Resources with sufficient technical information to make the determination.
(2) Bridges and culverts. Whereby the United States Army Corps of Engineers may require review, review by the Iowa Department of Natural Resources is not required for the proposed construction of new or replacement bridges or culverts where:
(a) The bridge or culvert is located on a stream that drains less than two square miles; and
(b) The bridge or culvert is not associated with a channel modification that constitutes a channel change as specified in 567-71.2(2), Iowa Administrative Code.
(3) Performance standards.
(a) All uses, or portions thereof, to be located in the floodway as determined by the Iowa Department of Natural Resources shall meet the applicable provisions and standards of the Floodway Overlay District.
(b) All uses, or portions thereof, to be located in the floodway fringe as determined by the Iowa Department of Natural Resources shall meet the applicable standards of the Floodway Fringe Overlay District.
(Q) Appeals.
(1) Appeals to Board of Adjustment. Where it is alleged there is an error in any order, requirement, decision, or determination made by an administrative official in the enforcement of this chapter, the aggrieved party may appeal such action. A request for an appeal shall be filed with the Zoning Administrator and shall set forth the specific reason for the appeal. The official from whom the appeal is taken shall transmit to the Board of Adjustment all the papers constituting the record upon which the action appealed from was taken.
(2) Appeals to the court. Any person or persons, jointly or severally, aggrieved by any decision of the Board of Adjustment may present to a court of record a petition, duly verified, setting forth that such decision is illegal, in whole or in part, specifying the grounds of the illegality. Such petition shall be presented to the court within 30 days after the filing of the decision in the office of the Board.
(R) Hearings. A public hearing is not required by the Board of Adjustment when acting on an appeal.
(S) Decisions. The Board shall arrive at a decision on an appeal, within a reasonable time. In passing upon an appeal, the Board may, so long as such action is in conformity with the provisions of this subchapter, reverse or affirm, wholly or in part, or modify the order, requirement, decision or determination appealed from and it shall make its decision, in writing, setting forth the findings of fact and the reasons for its decision.
(T) Floodplain Administrator decision factors. The Floodplain Administrator shall consider all relevant factors specified in other sections of this Zoning Ordinance and:
(1) The danger to life and property due to increased flood heights or velocities caused by encroachments.
(2) The danger that materials may be swept onto other lands or downstream to the injury of others.
(3) The proposed water supply and sanitation systems and the ability of these systems to prevent disease, contamination, and unsanitary conditions.
(4) The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner.
(5) The importance of the services provided by the proposed facility to the community.
(6) The requirements of the facility for a flood plain location.
(7) The availability of alternative locations not subject to flooding for the proposed use.
(8) The compatibility of the proposed use with existing development and development anticipated in the foreseeable future.
(9) The relationship of the proposed use to the comprehensive plan and flood plain management program for the area.
(10) The safety of access to the property in times of flood for ordinary and emergency vehicles. The expected heights, velocity, duration, rate of rise and sediment transport of the flood water expected at the site.
(11) The cost of providing governmental services during and after flood conditions, including maintenance and repair of public utilities (sewer, gas, electrical, and water systems), facilities, streets, and bridges.
(12) Such other factors which are relevant to the purpose of this chapter.
(U) Conditions.
(1) Upon consideration of the factors listed above, the Floodplain Administrator may attach such conditions to the approval as deemed necessary to further the purpose of this subchapter.
(2) Such conditions may include, but not necessarily be limited to:
(a) Modification of waste disposal and water supply facilities;
(b) Limitation on periods of use and operation;
(c) Imposition of operational controls, sureties, and deed restrictions; and
(d) Requirements for construction of channel modifications, dikes, levees, and other protective measures; provided, such are approved by the state’s Department of Natural Resources and are deemed the only practical alternative to achieving the purposes of this subchapter.
(V) Flood-proofing measures. Floodproofing measures shall be designed consistent with the flood protection elevation for the particular area, flood velocities, durations, rate of rise, hydrostatic and hydrodynamic forces, and other factors associated with the regulatory flood. The Floodplain Administrator shall require that the applicant submit a plan for document certified by a registered professional engineer or architect that the floodproofing measures are consistent with the regulatory flood protection elevation and associated flood factors for the particular area. Such floodproofing measures may include, but are not necessarily limited to the following:
(1) Anchorage to resist flotation and lateral movement.
(2) Installation of watertight doors, bulkheads, and shutters, or similar methods of construction.
(3) Reinforcement of walls to resist water pressures.
(4) Use of paints, membranes, or mortars to reduce seepage of water through walls.
(5) Addition of mass or weight structures to resist flotation.
(6) Installation of pumps to lower water levels in structures.
(7) Construction of water supply and waste treatment systems so as to prevent the entrance of flood waters.
(8) Pumping facilities or comparable practices for subsurface drainage systems for building to relieve external foundation wall and basement flood pressures.
(9) Construction to resist rupture or collapse caused by water pressure or floating debris.
(10) Installation of valves or controls on sanitary and storm drains which will permit the drains to be closed to prevent backup of sewage and stormwaters into the buildings or structures.
(11) Location of all electrical equipment, circuits, and installed electrical appliances in a manner that will assure they are not subject to flooding.
(W) Penalties for violations. Violations of the provisions of this article or failure to comply with any of the requirements shall be considered a municipal infraction punishable by civil penalty provided in § 10.999 of the Marshalltown Code of Ordinances.
(X) Amendments. The regulations, restrictions and boundaries set forth in this chapter may from time to time be amended, supplemented, changed, or repealed as provided in I.C.A. §§ 414.4, 414.5, and 414.21, 1977 as amended. No amendment, supplement, change, or modification to this chapter shall be undertaken without prior approval from the Iowa Department of Natural Resources.
(Ord. 15039, passed 4-11-2022)