Purpose. It is the purpose of this section to promote the public health, safety and general welfare by minimizing those flood losses described in subsection 2 below with provisions designed to:

1. A.
   Restrict or prohibit uses which are dangerous to health, safety or property in times of flood or which cause excessive increases in flood heights or flood water velocities;
2. B.
   Require that uses vulnerable to floods, including public utilities which service such uses, be protected against flood damage at the time of initial construction;
3. C.
   Assure that eligibility is maintained for property owners in the community to purchase flood insurance through the National Flood Insurance Program.

Findings of Fact. It is hereby declared that the flood plain 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 the occupancy of flood plain areas by uses vulnerable to flood damages which create hazardous conditions as a result of being inadequately elevated or otherwise protected from flooding and by the cumulative effect of flood plain construction on flood flows, which causes increases in flood heights and flood water velocities. This section relies upon engineering methodology for analyzing flood hazards which is consistent with the standards established by the Iowa Department of Natural Resources.

Compliance. No structure or land shall hereafter be used and no structures shall be located, extended, converted or structurally altered without full compliance with the terms of this section and other applicable regulations which apply to uses within the jurisdiction of this section.

Interpretation. In their interpretation and application, the provisions of these regulations shall be held to be minimum requirements for the promotion of the public health, safety, and general welfare.

Conflict. These regulations are not intended to interfere with, abrogate, or annul any other ordinance, rule or regulation, statute, or other provisions of law. Where any provision of these regulations imposes restrictions different from those imposed by any other provision of these regulations or regulations by any other ordinance, rules or regulations, or other provision of law, whichever provisions are more restrictive or impose higher standards shall control. These regulations are not intended to abrogate any easement, covenant or other private agreement or restriction provided that where the provisions of these regulations are more restrictive or impose higher standards or regulations than such easement, covenant, or other private agreement or restriction, the requirements of these regulations shall govern.

Warning and Disclaimer of Liability. The degree of flood protection required by these regulations 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 manmade or natural causes, such as ice jams and bridge openings restricted by debris. These regulations do not imply that areas outside the flood plain areas or land uses permitted within flood plain areas will be free from flooding or flood damages. These regulations shall not create liability on the part of the City or any officer or employee thereof for any flood damages that result from reliance on these regulations or any administrative decision lawfully made thereunder.

Amendments. Any regulations or provisions of this section may be changed and amended from time to time by the Council, after notice and hearings required by law. The Federal Insurance Administration and the Iowa Department of Natural Resources shall be notified of each amendment to the regulations or provisions of this section.

Flood Plain Management Overlay District Boundary.

1. A.
   These flood plain management regulations apply to all lands designated as special flood hazard areas. These special flood hazard areas are shown on the Flood Insurance Rate Maps for Polk County, Incorporated Areas, City of Grimes, Panels 19153C0155F, 0160F, 0165F, 0166F, 0167F, 0168F, 0169F, dated February 1, 2019, which were prepared as part of the Flood Insurance Study for Polk County, are hereby adopted by reference. The flood profiles and all explanatory material contained within the Flood Insurance Study are also declared to be a part of this ordinance.
2. B.
   The general location of the special flood hazard areas shall be determined by scaling distances on the Flood Insurance Rate Maps; however, in cases where a more precise determination is needed as to the exact location of the boundary in relation to a particular property, the determination shall be upon elevation, using the elevation reference mark set forth in the Flood Insurance Study.

Flood Plain Management Standards. All uses must be consistent with the need to minimize flood damage and shall meet the following applicable performance standards. Where 100-year flood data has not been provided in the Flood Insurance Study, the Department of Natural Resources shall be contacted to compute such data.

1. A.
   All structures shall be (1) 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.
2. B.
   Residential buildings. All new or substantially improved residential structures shall have the lowest floor (including basement) elevated a minimum of one (1) foot above the 100-year flood level. Construction shall be upon compacted fill which shall, at all points, be no lower than one (1) foot above the 100-year flood level and extend at such elevation at least eighteen (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 Council and the Department of Natural Resources, 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.
3. C.
   Non-residential structures. All new or substantially improved non-residential structures shall have the lowest floor (including basement) elevated a minimum of one (1) foot above the base flood elevation, or together with attendant utility and sanitary systems, be floodproofed to such a level. When floodproofing is utilized, a professional engineer registered in the State of Iowa shall certify that the floodproofing methods used are adequate to withstand the flood depths, pressures, velocities, impact and uplift forces and other factors associated with the base flood; and that the structure below the base flood elevation is watertight with walls substantially impermeable to the passage of water. A record of the certification indicating the specific elevation (in relation to North American Vertical Datum) to which any structures are floodproofed shall be maintained by the Administrator.
4. D.
   All new and substantially improved structures:

   1. 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 floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or meet or exceed the following minimum criteria:

      1. a.
         A minimum of two (2) openings having a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding shall be provided.
      2. b.
         The bottom of all openings shall be no higher than one (1) foot above grade.
      3. c.
         Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
      4. d.
         All such areas shall be used solely for parking of vehicles, building access and low damage-potential storage.
5. E.
   Factory-built homes:

   1. 1.
      All new and substantially improved 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 (1) foot above the 100-year flood level.
   2. 2.
      All new and substantially improved factory-built homes, including those placed in existing factory-built home parks or subdivisions, shall be anchored to resist floatation, collapse, or lateral movement. Anchorage systems may include, but are not limited to, use of over-the-top or frame ties to ground anchors as required by the State Building Code.

Utility and Sanitary Systems.

1. A.
   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 above the minimum floodproofing/flood protection elevation.
2. B.
   Onsite waste disposal systems shall be located or designed to avoid impairment to the system or contamination from the system during flooding.
3. C.
   New or replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system. Water supply treatment facilities shall be provided with a level of protection equal to or above the minimum floodproofing/flood protection elevation.
4. D.
   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.

Flood Control Structures. Flood control structural works such as levees and flood walls shall provide, at a minimum, protection from a 100-year flood with a minimum of three (3) feet of design freeboard and shall provide for adequate interior drainage. In addition, flood control structural works shall be approved by the Iowa Department of Natural Resources.

Subdivisions. Subdivisions (including factory-built 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 (including the installation of public utilities) shall meet the applicable performance standards of this ordinance. Subdivision proposals intended for residential use shall provide all lots with a means of access which will be passable by wheeled vehicles during the base flood. Proposals for subdivisions greater than five (5) acres or fifty (50) lots (whichever is less) shall include base flood elevation data for those areas located within the Special Flood Hazard Areas.

Storage of Materials. Storage of materials and equipment that are flammable, explosive or injurious to human, animal or plant life is prohibited unless elevated above the minimum floodproofing/flood protection elevation. 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.

Accessory Structures to Residential Uses.

1. A.
   Detached garages, sheds, and similar structures that are incidental to a residential use are exempt from the base flood elevation requirements where the following criteria are satisfied.

   1. 1.
      The structure shall be designed to have low flood damage potential. Its size shall not exceed six hundred (600) sq. ft. in size. Those portions of the structure located less than one (1) foot above the base flood elevation must be constructed of flood-resistant materials.
   2. 2.
      The structure shall be used solely for low flood damage potential purposes such as vehicle parking and limited storage. The structure shall not be used for human habitation.
   3. 3.
      The structure shall be constructed and placed on the building site so as to offer minimum resistance to the flow of floodwaters.
   4. 4.
      The structure shall be firmly anchored to resist flotation, collapse and lateral movement.
   5. 5.
      The structure’s service facilities such as electrical and heating equipment shall be elevated or floodproofed to at least one (1) foot above the base flood elevation.
   6. 6.
      The structure’s walls shall include openings that satisfy the provisions of Section 12-16-1(9)D1 of this chapter.
2. B.
   Exemption from the 100-year flood elevation requirements for such a structure may result in increased premium rates for flood insurance coverage of the structure and its contents.

Floodway Capacity. 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.

Channel Changes. 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.

Special Floodway Provisions. In addition to the General Flood Plain Standards, uses within the floodway must meet the following applicable standards. The floodway is that portion of the flood plain which must be protected from developmental encroachment to allow the free flow of flood waters. Where floodway data has been provided in the Flood Insurance Study, such data shall be used to define the floodway limits. Where no floodway data has been provided, the Iowa Department of Natural Resources shall be contacted to provide a floodway delineation.

1. A.
   No use shall be permitted in the floodway that would result in any increase in the 100-year flood level. Consideration of the effects of any development of flood levels shall be based upon the assumption that an equal degree of development would be allowed for similarly situated lands.
2. B.
   All uses within the floodway shall:

   1. 1.
      Be consistent with the need to minimize flood damage.
   2. 2.
      Use construction methods and practices that will minimize flood damage.
   3. 3.
      Use construction materials and utility equipment that are resistant to flood damage.
3. C.
   No use shall affect the capacity or conveyance of the channel or floodway or any tributary to the main stream, drainage ditch, or any other drainage facility or system.
4. D.
   Structures, buildings and sanitary and utility systems, if permitted, shall meet the applicable General Flood Plain Standards and shall be constructed or aligned to present the minimum possible resistance to flood flows.
5. E.
   Buildings, if permitted, shall have a low flood damage potential and shall not be for human habitation.
6. F.
   Storage of materials or equipment 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 within the time available after flood warning.
7. G.
   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 Department of Natural Resources.
8. H.
   Any fill allowed in the floodway must be shown to have some beneficial purpose and shall be limited to the minimum amount necessary.
9. I.
   Pipeline, river or stream crossings shall be buried in the stream bed and banks or otherwise sufficiently protected to prevent rupture due to channel degradation and meandering or due to the action of flood flows.

Duties and Responsibilities of Zoning Administrator. The Zoning Administrator shall administer and enforce the provisions of this section. Duties and responsibilities of the Zoning Administrator shall include, but not necessarily be limited to, the following:

1. A.
   Review all Flood Plain Development Permit applications to ensure that the provisions of this section will be satisfied.
2. B.
   Review all Flood Plain Development Permit applications to ensure that all necessary permits have been obtained from Federal, State or local governmental agencies.
3. C.
   Record and maintain a record of (1) the elevation (in relation to the North American Vertical Datum, 1988) of the lowest floor (including basement) of all new or substantially improved structures or (2) the elevation (in relation to the North American Vertical Datum, 1988) to which all new or substantially improved structures have been floodproofed.
4. D.
   Notify adjacent communities and/or Polk County and the Iowa Department of Natural Resources prior to any proposed alteration or relocation of a watercourse.
5. E.
   Keep a record of all permits, appeals, variances and such other transactions and correspondence pertaining to the administration of this section.

Flood Plain Development Permit Required. A Flood Plain Development Permit issued by the Administrator shall be secured prior to initiation of any flood plain development (any manmade change to improved or unimproved real estate, including, but not limited to, buildings or other structures, mining, filling, grading, paving, excavation or drilling operations) including the placement of factory-built homes.

Application for Permit. Application for a Flood Plain Development Permit shall be made on forms supplied by the Zoning Administrator and shall include the following information:

1. A.
   Description of the work to be covered by the permit for which application is to be made.
2. B.
   Description of the land on which the proposed work is to be done (i.e. – lot, block, tract, street address or similar description) that will readily identify and locate the work to be done.
3. C.
   Indication of the use or occupancy for which the proposed work is intended.
4. D.
   Elevation of the 100-year flood.
5. E.
   Elevation (in relation to the North American Vertical Datum, 1988) of the lowest floor (including basement) of buildings or of the level to which a building is to be floodproofed.
6. F.
   For buildings being improved or rebuilt, the estimated cost of improvements and market value of the building prior to the improvements.
7. G.
   Such other information as the Zoning Administrator deems reasonably necessary for the purpose of this section.

Action on Permit Application. The Zoning Administrator shall, within a reasonable time, make a determination as to whether the proposed flood plain development meets the applicable standards of this section and shall approve or disapprove the application. For disapprovals, the applicant shall be informed, in writing, of specific reasons therefore. The Zoning Administrator shall not issue permits for variances except as directed by the Board of Adjustment.

Construction and Use to be as Provided in Application and Plans. Flood Plain Development Permits issued on the basis of approved plans and applications authorize only the use, arrangement and construction set forth in such approved plans and application and no other use, arrangement or construction. Any use, arrangement, or construction at variance with that authorized shall be deemed a violation of this section. The applicant shall be required to submit certification by a professional engineer or land surveyor, as appropriate, registered in the State of Iowa, that the finished fill, building flood elevations, floodproofing, or other flood protection measures were accomplished in compliance with the provisions of this section, prior to the use or occupancy of any structure.

Variances. The Board of Adjustment may authorize upon request in specific cases such variances from the terms of this section that will not be contrary to the public interest where owing to special conditions, a literal enforcement of the provisions of this section will result in unnecessary hardship. Variances granted must meet the following applicable standards:

1. A.
   No variance shall be granted for any development within the floodway which would result in any increase in flood heights during the occurrence of the 100-year flood.
2. B.
   Variances shall only be granted upon:

   1. 1.
      Showing of good and sufficient cause;
   2. 2.
      A determination that failure to grant the variance would result in exceptional hardship to the applicant; and
   3. 3.
      A determination that the granting of the 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.
3. C.
   Variances shall only be granted upon a determination that the variance is the minimum necessary, considering the flood hazard, to afford relief.
4. D.
   In cases where the variance involves a lower level of flood protection for buildings than what is ordinarily required by this section, the applicant shall be notified in writing over the signature of the Zoning Administrator that:

   1. 1.
      The issuance of a variance will result in increased premium rates for flood insurance up to amounts as high as twenty-five dollars ($25.00) for one hundred dollars ($100.00) of insurance coverage; and
   2. 2.
      Such construction increases risks to lives and property.
5. E.
   All variances granted shall have the concurrence or approval of the Iowa Department of Natural Resources.

Factors upon Which the Decision of the Board of Adjustment Shall Be Based. In passing upon applications for variances, the Board of Adjustment shall consider all relevant factors specified in other parts of this section, and:

1. A.
   The danger to lives and property due to increased flood heights.
2. B.
   The danger that materials may be swept onto other lands or downstream to the injury of others.
3. C.
   The proposed water supply and sanitation systems and the ability of these systems to prevent disease, contamination and unsanitary conditions.
4. D.
   The susceptibility of the proposed facility and its contents to flood damage and the effect of such damage on the individual owner.
5. E.
   The importance of the services provided by the proposed facility to the City.
6. F.
   The requirements of the facility for a flood plain location.
7. G.
   The availability of alternative locations not subject to flooding for the proposed use.
8. H.
   The compatibility of the proposed use with existing development and development anticipated in the foreseeable future.
9. I.
   The relationship of the proposed use to the zoning and flood plain management program for the area.
10. J.
    The safety of access to the property in times of flood for ordinary and emergency vehicles.
11. K.
    The expected heights, velocity, duration, rate of rise and sediment transport of the flood water expected at the site.
12. L.
    Such other factors which are relevant to the purpose of this section.

Conditions Attached to Variances. Upon consideration of the factors listed above, the Board of Adjustment may attach such conditions to the granting of variances as it deems necessary to further the purpose of this section. Such conditions may include, but not necessarily be limited to:

1. A.
   Modification of waste disposal and water supply facilities.
2. B.
   Limitation on periods of use and operation.
3. C.
   Imposition of operational controls, sureties, and deed restrictions.
4. D.
   Requirements for construction of channel modifications, dikes, levees, and other protective measures, provided such are as approved by the Iowa Department of Natural Resources and are deemed the only practical alternative to achieving the purpose of this section.
5. E.
   Flood proofing measures.

The Legislator of the State of Iowa has in Chapter 414, Code of Iowa, as amended, delegated the power to cities to enact zoning regulations to secure safety from flood and to promote health and the general welfare.

Severability. If any section, clause, provision or portion of this ordinance is adjudged unconstitutional or invalid by a court of competent jurisdiction, the remainder of this ordinance shall not be affected thereby.