Article 24 — FH (Flood Hazard) Overlay Zone

The Flood Hazard Overlay Zone identifies areas where terrain characteristics would present new developments and their users with potential hazards to life and property from potential inundation by a 100 year frequency flood or other known flood hazards. These standards are also intended to minimize the effects of development on drainage ways and watercourses.

(Ord. 68 § 9-3.601, 1983)

All uses proposed within a Flood Hazard Overlay Zone are subject to the standards of Sections 9-3.602 through 93.604 , except:

• (a) Temporary Uses. With the approval of the City Engineer, the Planning Department may authorize construction or placement of a temporary structure or use within a Flood Hazard Overlay Zone pursuant to the required approval without meeting these standards, provided that the structure or use will not be in place from October 15th to April 15th.

• (b) Emergency Work. Emergency work may be undertaken where necessary to preserve life or property. Within 48 hours after commencement of such work, the City Engineer is to be notified and an application filed with the Planning Department in compliance with the provisions of Section 9-3.603 .

• (c) Existing Uses. The continuance, operation, repair, or maintenance of any lawful use of land existing on the effective date of this title is permitted. Any expansion of an existing structure or use, or grading of a site, shall be conducted in accordance with all applicable provisions of this title.

• (Ord. 68 § 9-3.602, 1983)

Drainage plan approval is required where any portion of the proposed development of the site is located within a Flood Hazard Overlay Zone. In addition to the information called for in Section 9-4.149 the drainage plan is to include:

• (a) A normal depth analysis or other equivalent engineering analysis that demonstrates to the satisfaction of the City Engineer that proposed structures will not be located within the floodway. The following information is required to determine the location of the floodway, except where waived or modified by the City Engineer:

  • (1) Plans drawn to scale showing the location, dimensions, and elevation of the lot, existing or proposed structures, fill, storage of materials, floodproofing measures, and the relationship of the above to the location of the floodway.

  • (2) Typical valley cross-sections showing the normal channel of the stream, elevation of the land areas adjoining each side of the channel, cross-sections of areas to be occupied by the proposed development, and highwater information sufficient to define the 100 year storm flood profile level.

  • (3) A profile showing the slope of the bottom of the channel or flow line of the stream.

• (b) Where data required by subsection (a) of the section indicates proposed structures are located outside the floodway but within the flood fringe, a structural plan is to be provided for review and approval by the City Engineer. The plan is to demonstrate that proposed structures are designed to be flood free or be able to withstand partial inundation, and that proposed uses will not subject occupants to undue risk of flooding. Such structural plans are to include, where applicable, specifications for building construction, dredging, grading, channel improvement, storage of materials, water supply, and sanitary facilities.

• (Ord. 68 § 9-3.603, 1983)

Any structure or construction activities within a Flood Hazard Overlay Zone are subject to the following:

• (a) Construction, General.

  • (1) No construction or grading is to limit the capacity of the floodway or increase flood heights above that allowed under the Federal Flood Insurance Program.

  • (2) Structures are to be anchored to prevent flotation that could result in damage to other structures, or restriction of bridge openings and narrow sections of the stream or river.

  • (3) Service facilities such as electrical and heating equipment are to be floodproofed or constructed at a minimum of one foot above the one hundred (100) year storm flood profile level for the site.

• (b) Structures for Human Occupancy. All structures intended for human occupancy are subject to the following standards, in addition to the provisions of subsection (a) of this section:

  • (1) A structure intended for human occupancy is to be approved only where the City Engineer certifies that all portions of the structure are located outside the floodway on the basis of the depth analysis submitted in accordance with Section 9-3.603 .

  • (2) On the basis of structural plans and the depth analysis the ground floor of all structures is to be constructed at a minimum of one foot above the 100 year storm flood profile level.

• (c) Storage and Processing. The storage or processing of materials that in time of flooding are buoyant, inflammable or explosive; that could be injurious to human, animal, or plant life; or that may unduly affect the capacity of the floodway or unduly increase flood heights is not permitted. Storage of other material or equipment may be allowed if not subject to major damage by floods and if firmly anchored to prevent flotation, or if readily removable from the area within the time available after flood warning.

• (Ord. 68 § 9-3.604, 1983)