In all areas of special flood hazards where base flood elevation data has been provided as set forth in section 4-4-7 of this chapter, the following provisions are required:
A. Residential Construction:
1. New construction and substantial improvement of any residential structure shall have a finish floor elevation of one foot (1') above the base flood elevation and the lowest floor, including basement and crawl space, shall be elevated to a minimum of one foot (1') above the base flood elevation.
2. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or 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 must meet or exceed the following minimum criteria:
a. A minimum of two (2) 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 (1') above grade.
c. Openings may be equipped with screens, louvers or their coverings or devices, provided that they permit the automatic entry and exit of floodwaters.
B. Nonresidential Construction: New construction and substantial improvement of any commercial, industrial or any other nonresidential structure shall either have the finish floor elevation of the lowest floor, including basement, elevated to one foot (1') above the base flood elevation or, together with attendant utility and sanitary facilities, shall:
1. Be floodproofed to a point one foot (1') above the base flood elevation so that the structure is watertight with walls substantially impermeable to the passage of water;
2. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;
3. Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth in subsection 4-4-11C of this chapter.
4. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection A2 of this section.
5. Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot (1') below the floodproofed level (e.g., a building constructed to the base flood level will be rated as 1 foot below that level).
C. Manufactured Homes:
1. All manufactured homes to be placed or substantially improved within Zones A1-30, AH and AE, which meet one of the following location criteria, shall be elevated on a permanent foundation such that the finish floor elevation of the lowest floor of the manufactured home is one foot (1') above the base flood elevation and be securely anchored by methods constructed in conformance with sections 5-4-1 through 5-4-4 of this Code:
a. Outside a manufactured home park or subdivision;
b. In a new manufactured home park or subdivision;
c. In an expansion to an existing manufactured home park or subdivision; or
d. On a site in an existing manufactured home park or subdivision, which manufactured home has incurred substantial damage as a result of a flood.
2. All manufactured homes to be placed or substantially improved in an existing manufactured home park shall be elevated so that either:
a. The lowest floor of the manufactured home is elevated to the flood protection elevation or one foot (1') above the level of the base flood elevation, whichever is higher; or
b. The manufactured home chassis is elevated and supported by reinforced piers (or other foundation elements of at least an equivalent strength) of no less than thirty six inches (36") above the highest adjacent grade.
D. Recreational Vehicle Requirements: All recreational vehicles in Zones A1-30, AH and AE to be placed on a site must:
2. Be on the site for less than one hundred eighty (180) consecutive days; or
3. Be fully licensed and highway ready on its wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached structures or addition.
E. Elevation Certificates: Elevation certificates shall be required for all structures in the SFHA, special flood hazard area issued by FEMA, the Federal Emergency Management Agency and shall comply with all standards set forth in this chapter. When completing elevation certificates on properties removed from SFHA, use base flood elevation insurance prior to removal from SFHA.
F. Setback: All buildings shall be set back a minimum of fifty feet (50') from the floodway line except that when the area of special flood hazard boundary is fifty feet (50') or less from the floodway line, the boundary line shall be the setback line.
G. Floodways: Located within areas of special flood hazard are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles and erosion potential, the following provisions apply:
1. No Rise: Encroachments, including fill, new construction, substantial improvements and other development, are prohibited unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood. If this section is satisfied, development within the floodway shall comply with all applicable flood hazard reduction provisions of this chapter.
2. Mitigation To Achieve No Rise: Compensating excavation in accordance with an engineered plan for orderly conveyance of floodwater, or equivalent mitigating measures may be performed in the floodway when certified by a registered professional engineer or architect. Mitigation design shall include provisions to prevent relocation or diversion of flow paths from causing increased jeopardy to any off site property at any level of flooding from the 1-year flood up to the base flood. Provisions shall be made in a recorded development agreement between the City and the applicant to maintain excavated areas prone to fill from sediment and other debris as follows:
a. A plan and schedule for the future maintenance of the floodway for the period of the expected lifetime thereof and a cost estimate therefor prepared by a licensed professional engineer in the State, together with a proposed method for funding the same including, but not limited to, the creation and maintenance of a Reserve Fund for that purpose, shall be submitted to the City Council for review and approval prior to the execution of the final plat by the City. The location of the floodway to be maintained shall be clearly depicted on the face of the final plat.
b. A restrictive covenant for maintenance of the floodway shall be recorded at the time of recording the plat which said covenant shall create a homeowners'/property owners' association or substantially similar entity and make provision for the perpetual maintenance of the floodway. Said restrictive covenant shall also provide that the covenant shall run with the land and that said covenant cannot be modified or the homeowners'/property owners' association or other entity cannot be dissolved without the express consent of the City.
c. The Council may, in the reasonable exercise of its discretion, order the owners or the entity responsible for the maintenance of the floodway to undertake such maintenance activities as it may determine are necessary to protect the public health, safety and welfare and make such expenditures from the funds reserved therefor as may be required thereby; and the owner or responsible entity shall, as a condition of approval of floodway excavation, be deemed to have agreed to comply with any such order and to reimburse the City all its costs, including attorney fees, incurred in obtaining or enforcing any such order. Any order entered by the Council pursuant to this subsection may be enforced by a court of competent jurisdiction and the City shall be entitled to recover its costs and attorney fees incurred in connection therewith.
3. Emergency Access: Where setback from the floodway line is less than one hundred feet (100') but more than fifty feet (50'), compensating measures shall be designed to protect a fifty foot (50') wide access strip for emergency construction equipment. Compensating measures shall be constructed as designed and certified by a professional engineer.
4. Parks And Open Spaces: In the design of public and private parks and open space areas, fixed structures or equipment that would impede floodwaters shall not be permitted within the floodway.
5. Access: Any nonfloodway area surrounded by floodway shall be accessed by at least one road with suitable structures or culverts to pass floodwaters. If a bridge is required, it shall be elevated one foot (1') above the base flood elevation, have scour resistant footings extending to five feet (5') below the bottom of the channel and be capable of supporting an H-15 load as defined by the American Association of State Highway and Transportation Officials (AASHTO).
H. Map And Narrative Required: All subdivision proposals and development permit applications shall provide a map and detailed narrative describing any abutting or on site manmade topographic features, current or proposed, that increase flood damage potential above the natural level, including road fills and other manmade embankments, prior stream channelization, existing and/or proposed landscaping features, and evident agricultural land leveling that has altered the floodplain from its original topography.
I. Fill Requirements: For fill placed in the regulatory special flood hazard area:
1. The slope of fill adjacent to the floodway line, hereinafter called the floodway boundary slope, shall not be steeper than five horizontal to one vertical (5:1). Where a five to one (5:1) slope is not feasible due to lot dimensions, compensating measures to protect against floodway encroachment through erosion shall be constructed as designed and certified by a professional engineer, architect, or landscape architect.
2. The floodway boundary slope shall be maintained with adequate ground cover to prevent erosion.
J. Roadways And Manholes: Roadways and manholes within the regulatory floodplain shall be a minimum of one-half foot (0.5') above base flood elevation at centerline and manhole ring respectively.
K. Flow Paths Maintained: New roads built above the base flood elevation shall not block or restrict conveyance of floodwater into sections of the floodplain that may be cut off by the proposed road and shall have culverts or bridges for flood conveyance paths.
L. Open Areas: Except for required berms, open areas such as parks, golf courses, greenbelt areas, parking lots, etc., within the area of special flood hazard shall be designed and operated so that they may flood and maintain existing natural flood paths for waters during the base flood event.
M. Flood Study: When a new flood study is provided by the developer:
1. The study shall be performed using the U.S. Army Corps of Engineers Hydrologic Engineering Center's HEC-2, HEC-RAS (river analysis system), or equivalent programs to calculate water surface elevations.
2. Describe methods to detain drainage contribution to the base flood event discharge.
3. The study report shall include field survey data and relevant bench marks used as bases of calculations as cross sections, stream profile and plan showing cross section locations.
4. The study report shall attach HEC-2, HEC-RAS, or equivalent input and output reports as an appendix.
5. Any floodway or regulatory floodplain modification shall not be effective until approved by FEMA.
6. The study shall include a reach of stream extending beyond the property boundaries of the development upstream and downstream as required to comply with FEMA guidelines.
7. Demonstrate that the cumulative effect of any proposed development, when combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than one foot (1') at any point.
N. Critical Facilities: Critical facilities shall not be allowed within any special flood hazard area, including areas designated as subject to inundation by the 0.2 percent annual chance flood event, also known as the 500-year flood and shown as shaded Zone X areas on FIRM maps. (Ord. 593, 5-13-2019)