In all special flood hazards areas where base flood elevation data is established, the provisions of this section shall be required:
A. Residential Construction:
1. Connection to a central sewage treatment system shall be required. Residential development within the regulatory floodplain may be clustered (through approval of the City) to facilitate the economics of the sewage infrastructure.
2. New construction, including installed manufactured homes, and substantial improvement of any residential structure shall have:
a. The lowest finished floor elevation a minimum of one foot (1') above the base flood elevation;
b. The lowest floor elevation at least one foot (1') above the base flood elevation;
c. All building utility systems, including electrical, heating, ventilation, plumbing, air conditioning, ductwork and other facilities elevated at least one foot (1') above the base flood elevation.
B. Nonresidential Construction: New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor elevation at least two feet (2') above the base flood elevation; or, together with attendant utility and sanitary facilities, shall:
1. Be floodproofed to a point two feet (2') 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; and
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 4-3-8A of this chapter.
4. 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 elevation will be rated as 1 foot below that level).
C. For new and substantially improved structures, fully enclosed areas below the lowest floor that are usable solely for parking vehicles, building access, or storage in an area other than a basement or crawl space and that are subject to flooding shall be elevated according to the requirements of this chapter or shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for this requirement must either be certified by a registered professional engineer or architect, or must meet or exceed the following minimum criteria:
1. A minimum of two (2) openings, having a total net area of at least one (1) square inch for every square foot of enclosed area subject to flooding, shall be provided.
2. The bottom of all openings shall be no higher than one foot (1') above adjacent grade.
3. Openings may be equipped with screens, louvers, or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters.
D. Elevation Certificates: Elevation certificates shall be required for all structures in the SFHA, special flood hazard area, or on land formerly in the SFHA, regardless of any LOMR-F, letter of map revision based on fill, 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 data prior to removal from SFHA.
E. 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.
F. 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 within the adopted regulatory floodway are prohibited unless it has been demonstrated through hydrologic and hydraulic analyses performed according to 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.
2. 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.
3. 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). Construction of bridges or culverts in floodways shall comply with the “no-rise” certification provisions of this chapter or, prior to construction, a Conditional Letter of Map Revision and follow-up Letter of May Revision, if needed, shall have been submitted to the Federal Emergency Management Agency for review and acknowledgment.
G. 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.
H. 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.
I. 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.
J. 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.
K. 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.
L. 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 FEMA-approved 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 modification of a FEMA-established base flood elevation, floodway or regulatory floodplain 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.
M. 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.
N. Recreational vehicles shall be either on-site fewer than one hundred eighty (180) consecutive days and be fully licensed and ready for highway use or in compliance with the elevation and anchoring requirements for manufacturers homes. 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.
(Ord. 531, 4-2-2014; amd. Ord. 568, 12-21-2015; Ord. 609, 7-3-2018; Ord. 618, 6-5-2019)