§ 18-74. Building standards for streams without established base flood elevations (approximate A-zones).

Located within the areas of special flood hazard established in section 18-22, where streams exist but no base flood data have been provided (approximate A-zones), the following provisions apply:

(1)

Base flood elevation data shall be provided for subdivision proposals and all other proposed development, including manufactured home parks and subdivisions, greater than 50 lots or five acres, whichever is the lesser.

(2)

When base flood elevation data or floodway data have not been provided in accordance with section 18-22 then the floodplain administrator shall obtain, review, and reasonably utilize any scientific or historic base flood elevation and floodway data available from a federal, state, or other source, in order to administer the provisions of article IV. Only if data are not available from these sources, then subsections 18-74(5) and (6) shall apply.

(3)

No encroachments, including structures or fill material, shall be located within an area equal to the width of the stream or 25 feet, whichever is greater, measured from the top of the stream bank, unless certification by a registered professional engineer is provided demonstrating that such encroachment shall not result in any increase in flood levels during the occurrence of the base flood discharge.

(4)

All development in zone A must meet the requirements of section 18-71 and subsections 18-72(1)—(4).

(5)

In special flood hazard areas without base flood elevation data, new construction and substantial improvements of existing structures shall have the lowest floor (for the lowest enclosed area; including basement) elevated no less than three feet above the highest adjacent grade.

(6)

In the absence of a base flood elevation, a manufactured home must also meet the elevation requirements of subsection 18-72(4)b.2. in that the structure must be elevated to a maximum of 60 inches (five feet).

(7)

Openings sufficient to facilitate automatic equalization of flood water hydrostatic forces on exterior walls shall be provided in accordance with standards of subsection 18-72(3)a. The floodplain administrator shall certify the lowest floor elevation level and the record shall become a permanent part of the permit file.

(8)

Fill within the area of special flood hazard shall result in no net loss of natural floodplain storage. The volume of 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. Any excavation or other measures taken for compensatory storage shall be properly designed to provide protection against erosion or overgrowth of vegetation in order to preserve the storage volume. Proper maintenance measures shall also be undertaken to ensure the intended storage volume remains in perpetuity.

(Ord. No. 2018-9 , Art. 4(§ D), 8-6-2018)