City of Duquesne, MO Article IV Provisions For Flood Hazard Reduction

Section 430.150 General Standards.

[Ord. No. 211 § 1, 12-12-2012; Ord. No. 550, 7-21-2025]

A. No permit for floodplain development shall be granted for new construction, substantial improvements, and other improvements, including the placement of manufactured homes, within any unnumbered or numbered A zones and AE zones, unless the conditions of this Section are satisfied.

B. All areas identified as unnumbered A zones on the FIRM are subject to inundation of the 100-year flood; however, the base flood elevation is not provided. Development within unnumbered A zones is subject to all provisions of this Chapter. If Flood Insurance Study data is not available, the community shall obtain, review, and reasonably utilize any base flood elevation or floodway data currently available from Federal, State, or other sources.

C. Until a floodway is designated, no new construction, substantial improvements, or other development, including fill, shall be permitted within any numbered A zone or AE zone on the FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one (1) foot at any point within the community.

D. All new construction, subdivision proposals, substantial improvements, prefabricated structures, placement of manufactured homes, and other developments shall require:

1. Design or adequate anchorage to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy;

2. Construction with materials resistant to flood damage;

3. Utilization of methods and practices that minimize flood damages;

4. All electrical, heating, ventilation, plumbing, air-conditioning equipment, and other service facilities be designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding;

5. New or replacement water supply systems and/or sanitary sewage systems be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters, and on-site waste disposal systems be located so as to avoid impairment or contamination; and

6. Subdivision proposals and other proposed new development, including manufactured home parks or subdivisions, located within special flood hazard areas are required to assure that:

a. All such proposals are consistent with the need to minimize flood damage;

b. All public utilities and facilities, such as sewer, gas, electrical, and water systems are located and constructed to minimize or eliminate flood damage;

c. Adequate drainage is provided so as to reduce exposure to flood hazards; and

d. All proposals for development, including proposals for manufactured home parks and subdivisions, greater than five (5) acres or fifty (50) lots, whichever is lesser, include within such proposals base flood elevation data.

E. Agricultural Structures. Structures used solely for agricultural purposes in connection with the production, harvesting, storage, drying, or raising of agricultural commodities, including the raising of livestock, may be constructed at-grade and wet-floodproofed, provided there is no human habitation or occupancy of the structure, the structure is of single-wall design, there is no permanent retail, wholesale, or manufacturing use included in the structure, a variance has been granted from the floodplain management requirements of this Chapter, and a floodplain development permit has been issued.

F. Storage, Material, And Equipment.

1. The storage or processing of materials within the special flood hazard area that are in time of flooding buoyant, flammable, explosive, or could be injurious to human, animal, or plant life is prohibited.

2. Storage of other material or equipment may be allowed if not subject to major damage by floods, if firmly anchored to prevent flotation or if readily removable from the area within the time available after a flood warning.

G. Accessory Structures. Structures used solely for parking and limited storage purposes, not attached to any other structure on the site, of limited investment value, and not larger than four hundred (400) square feet, may be constructed at-grade and wet-floodproofed provided there is no human habitation or occupancy of the structure, the structure is of single-wall design; a variance has been granted from the standard floodplain management requirements of this Chapter, and a floodplain development permit has been issued.

H. Hazardous Materials. All hazardous material storage and handling sites shall be located out of the special flood hazard area. Refer to Section 430.290 for the definition of a hazardous material.

I. Compensatory Storage Required For Fill. Fill within the special flood hazard area shall result in no net loss of natural floodplain storage or increase in water surface elevations during the base flood. The volume of the loss of floodwater storage due to filling in the special flood hazard area shall be offset by providing an equal volume of flood storage by excavation or other compensatory measures at or adjacent to the development site.

J. Critical Facilities.

1. All new or substantially-improved critical non-residential facilities, including, but not limited, to governmental buildings, Police stations, fire stations, hospitals, orphanages, penal institutions, communication centers, water and sewer pumping stations, water and sewer treatment facilities, transportation maintenance facilities, places of public assembly, emergency aviation facilities, and schools shall be elevated above the 500-year flood level or together with attendant utility and sanitary facilities, be floodproofed so that below the 500-year flood level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy. A registered professional engineer or architect shall certify that the standards of this Subsection are satisfied. Such certification shall be provided to the Floodplain Administrator as set forth in the National Flood Insurance Program (NFIP) regulations.

2. All critical facilities shall have access routes that are above the elevation of the 500-year flood.

3. No critical facilities shall be constructed in any designated floodway.

K. Non-Conforming Use. A structure, or the use of a structure or premises that was lawful before the passage or amendment of this Chapter, but which is not in conformity with the provisions of this Chapter, may be continued subject to the following conditions:

1. If such structure, use, or utility service is discontinued for six (6) consecutive months, any future use of the building shall conform to this Chapter.

2. If any non-conforming use or structure is destroyed by any means, including flood, it shall not be reconstructed if the cost is more than fifty percent (50%) of the pre-damaged market value of the structure. This limitation does not include the cost of any alteration to comply with existing State or local health, sanitary, building, safety codes, regulations or the cost of any alteration of a structure listed on the National Register of Historic Places, the State Inventory of Historic Places, or local inventory of historic places upon determination.

L. Fill Standards. The following standards apply to all fill activities in special flood hazard areas:

1. Fill sites, upon which structures will be constructed or placed, must be compacted to ninety-five percent (95%) of the maximum density obtainable with the Standard Proctor Test method or an acceptable equivalent method;

2. Fill slopes shall not be steeper than one (1) foot vertical to two (2) feet horizontal;

3. Adequate protection against erosion and scour is provided for fill slopes. When expected velocities during the occurrence of the base flood are greater than five (5) feet per second, armoring with stone or rock protection shall be provided. When expected velocities during the base flood are five (5) feet per second or less, protection shall be provided by covering them with vegetative cover;

4. Fill shall be composed of clean granular or earthen material.

M. Temporary Structures. A temporary structure is strictly permitted only by special use permit issued by the Governing Body of the community. Any application for a special use permit to allow a temporary structure will be reviewed for compliance with all existing ordinances and Codes, including the special use permit regulations.

Section 430.160 Specific Standards.

[Ord. No. 211 § 1, 12-12-2012; Ord. No. 550, 7-21-2025]

A. In all areas identified as unnumbered and numbered A Zones, AE and AH Zones, where base flood elevation data have been provided, as set forth in Article IV, Section 430.150(B), the following provisions are required:

1. Residential Construction. New construction or substantial-improvement of any residential structures, including manufactured homes, shall have the lowest floor, including basement, elevated to two (2) feet[1] above base flood level. The elevation of the lowest floor shall be certified by a Missouri licensed land surveyor, engineer, or architect.

[1] Note: The FEMA, Region VII office recommends elevating to one (1) foot above the base flood elevation to qualify for flood insurance rates based upon floodproofing.

2. Non-Residential Construction. New construction or substantial-improvement of any commercial, industrial, or other non-residential structures, including manufactured homes, shall have the lowest floor, including basement, elevated to two (2) feet above the base flood level or, together with attendant utility and sanitary facilities, be floodproofed so that below the base flood elevation the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. A registered professional engineer or architect shall certify that the standards of this Subsection are satisfied. Such certification shall be provided to the Floodplain Administrator as set forth in Article III, Section 430.130(7), (8) and (9).

3. Require, for all new construction and substantial improvements, that fully enclosed areas below lowest floor used solely for parking of vehicles, building access, or storage in an area other than a basement and 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 architect or meet or exceed the following minimum criteria:

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; and

b. The bottom of all openings shall be no higher than one (1) foot above grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters.

Section 430.170 Manufactured Homes.

[Ord. No. 211 § 1, 12-12-2012; Ord. No. 550, 7-21-2025]

A. All manufactured homes to be placed within all unnumbered and numbered A Zones and AE Zones on the community's FIRM shall be required to be installed using methods and practices that minimize flood damage. For the purposes of this requirement, manufactured homes must be elevated and anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors.

B. Require manufactured homes that are placed or substantially improved within unnumbered or numbered A Zones, AE and AH Zones on the community's FIRM on sites:

1. Outside of a manufactured home park or subdivision;

2. In a new manufactured home park or subdivision;

3. In an expansion to an existing manufactured home park or subdivision; or

4. In an existing manufactured home park or subdivision on which a manufactured home has incurred substantial damage as the result of a flood,

be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to two (2) feet above the base flood elevation and be securely attached to an adequately anchored foundation system to resist flotation, collapse, and lateral movement. The elevation of the lowest floor shall be certified by a Missouri licensed land surveyor, engineer, or architect.

C. Require that manufactured homes be placed or substantially improved on sites in an existing manufactured home park or subdivision within all unnumbered and numbered A Zones, AE and AH Zones, on the community's FIRM, that are not subject to the provisions of Article IV, Section 430.170(B) of this Chapter, be elevated so that either:

1. The lowest floor of the manufactured home is two (2) feet above the base flood elevation; or

2. The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than thirty-six (36) inches in height above grade and be securely attached to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

Section 430.180 Determination Of Floodways; Standards.

[Ord. No. 211 § 1, 12-12-2012]

A. If a community determines there are areas of special flood hazard that may be defined as floodway through the use of base flood elevation and floodway data available from a Federal, State, or other source, including data developed pursuant to Article IV, Section 430.150(D)(6)(d), and determines this data is suitable as criteria for requiring that new construction, substantial improvements, or other development in Zone A, the community must meet the standards below:

1. Adopt a regulatory floodway based on the principle that the area chosen for the regulatory floodway must be designed to carry the waters of the base flood without increasing the water surface elevation of that flood more than one (1) foot at any point.

2. Prohibit encroachments, including fill, new construction, substantial improvements, and other development within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels within the community during the occurrence of the base flood discharge.

Section 430.190 Recreational Vehicles.

[Ord. No. 211 § 1, 12-12-2012; Ord. No. 550, 7-21-2025]

A. Require that recreational vehicles placed on sites within all unnumbered and numbered A Zones AO, AE, and AH Zones on the community's FIRM either:

1. Be on the site for fewer than one hundred eighty (180) consecutive days;

2. Be fully licensed and ready for highway use*; or

3. Meet the permitting, elevation, and anchoring requirements for manufactured homes of this Chapter.

*	A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick-disconnect type utilities and security devices and has no permanently attached additions.