7.75.010 Purpose. The purpose of the Flood Hazard Overlay is to promote the public health, safety and general welfare; protect human life and health; minimize expenditure of public money and costly flood control projects; minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public; minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in areas of special flood hazard; ensure that the public has access to information that property is in an area of special flood hazard; and maintain compliance with the National Flood Insurance and Hazard Mitigation Program

7.75.020 Definitions. For the purpose of this chapter, the following words, terms and expressions shall be interpreted in accordance with the following definitions, unless the context requires otherwise.

A. Area of Shallow Flooding: Area designated AO or AH on the Flood Insurance Rate Map (FIRM). The base flood depths range from one to three feet; a clearly defined channel does not exist; the path of flooding is unpredictable and indeterminate; and velocity flow may be evident. AO is characterized as sheet flow and AH indicates ponding.

B. Area of Special Flood Hazard: The land in the floodplain within a community subject to a one percent or greater chance of flooding in any given year.

C. Base Flood: The flood having a one percent chance of being equaled or exceeded in any given year. The base flood is also referred to as the "100-year flood."

D. Flood or Flooding: A general and temporary condition of partial or complete inundation of normally dry land areas from:

The overflow of inland or tidal waters; and/or

The unusual and rapid accumulation of runoff of surface waters from any source.

E. Food Insurance Rate Map (FIRM): The official map on which the Federal Insurance Administration has delineated both the areas of special flood hazards and the risk premium zones applicable to the community.

F. Floodway: The channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot.

G. Lowest Floor: The lowest enclosed area (including basement). An unfinished or flood resistant enclosure, usable solely for parking of vehicles, building access or storage, in an area other than a basement area is not considered a building's lowest floor, provided that such enclosure allows the entry and exit of flood waters.

H. New Construction: Structures for which the start of construction commenced on or after the adoption date of this ordinance.

I. Start of Construction: Includes substantial improvement, and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, placement or other improvement was within 180 days of the permit date. The actual start means either the first placement of permanent construction of a structure on a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the state of excavation; or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading and filling; nor does it include the installation of streets and/or walkways; nor does it include excavation for a basement, footings, piers, or foundation or the erection of temporary forms; nor does it include the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or not part of the main structure.

J. Structure: A walled and roofed building including a gas or liquid storage tank that is principally above ground.

K. Substantial Improvement: Any allowed repair, reconstruction, or improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure either:

1. Before the improvement or repair is started, or

2. If the structure has been damaged and is being restored, before the damage occurred. For the purposes of this definition, "substantial improvement" is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure. The term does not, however, include either any project for improvement of a structure to comply with existing state or local health, sanitary or safety code specifications which are solely necessary to assure safe living conditions, or any alteration of a structure listed on the National Register of Historic Places or a State Inventory of Historic Places.

7.75.030 Applicability. The Flood Hazard Overlay shall be applicable to all properties which are identified as areas of special flood hazard identified by the Federal Insurance Administration on the Flood Insurance Maps dated August 16, 1988. These maps are hereby adopted by reference and declared to be a part of this Ordinance. The City shall utilize all authoritative information available in determining the location of special flood hazard areas.

7.75.040 Permitted Uses. For all properties located outside the riparian corridor as defined by the OAR 660-023-0090, uses within the Flood Hazard Overlay shall be as permitted in the base zoning. For properties located inside the riparian corridor, uses shall be as permitted by OAR 660-023.

7.75.045 Conditional Uses. For all properties located outside the riparian corridor as defined by the OAR 660-023-0090, conditional uses within the Flood Hazard Overlay shall be the conditional uses in the base zoning. For properties located inside the riparian corridor, conditional uses shall be as permitted by OAR 660-023.

7.75.050 Disclaimer of Liability. The degree of flood protection required by this ordinance is considered reasonable for regulatory purposes and is based on scientific and engineering flood plain standards prepared by the Federal Insurance Administration. Larger floods can and will occur on rare occasions. Flood heights may be increased by man-made or natural causes. This ordinance does not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages. This ordinance shall not create liability on the part of the Columbia City, any officer or employee thereof, or the Federal Insurance Administration, for any flood damages that result from reliance on this ordinance or any administrative decision lawfully made thereunder.

7.75.060 Administration.

A. The City Administrator shall review all development applications including fill permits, subdivision and partition applications to determine if the property is subject to this chapter. Upon determination that the property is located within the Flood Hazard Zone, the applicant shall be required to satisfy the requirements of this chapter.

B. The Planning Director shall make interpretations where needed as to exact location of the boundaries of the areas of flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions).

C. The City Administrator shall notify all applicants flood-proofing nonresidential buildings that flood insurance premiums will be based on rates that are one foot below the flood-proofed level (e.g., a building constructed to the base flood level will be rated as one foot below that level).

D. When an alteration to a waterway is proposed, the Planning Director shall notify adjacent communities, the Division of State Lands and the Oregon Department of Land Conservation and Development prior to any alteration or relocation of a watercourse, and submit evidence of such notification to the Federal Insurance Administration.

E. The City Administrator shall maintain for public inspection the following records:

1. Where base flood elevation data is provided through the Flood Insurance Map or by the applicant, a record of the actual elevation (in relation to mean sea level) of the lowest habitable floor (including basement) of all new or substantially improved structures, and whether or not the structure contains a basement.

2. For all new or substantially improved floodproofed structures, a record the actual elevation (in relation to the mean sea level) and the floodproofing certifications.

3. For all new or substantially improved non residential structures, the certification that the floodproofing methods and elevations meet the floodproofing criteria in Section 7.75.070 (H).

7.75.070 Standards. Approval of applications for development in the Flood Plain Overlay Zone shall be based upon the following findings:

A. All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure.

B. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

C. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.

D. Electrical, heating, ventilation, plumbing, air-conditioning equipment and other service facilities shall be elevated one (1) foot above the 100 year flood plain so as to prevent water from entering or accumulating within components during conditions of flooding.

E. All new and replacement water supply systems shall be designed to prohibit infiltration of flood waters into the system;

F. New and replacement sanitary sewage systems shall be designed to prohibit infiltration of flood waters into the systems and discharge from the systems into flood waters. No on-site disposal systems shall be allowed.

G. Where base flood elevations data has been provided:

1. Substantial improvement of any existing residential structure shall have the lowest floor, including basement, elevated to one foot above base flood elevations. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited. Parking, crawl spaces and storage is allowed below the lowest floor provided the area is designed to permit the entry and exit of floodwaters.

2. Substantial improvement of any existing commercial, industrial or other nonresidential structure, or new construction, under the permitted and conditional use of Section 7.75.030 and 7.75.040 above, located within number A zones (as defined by the Federal Emergency Management Agency) shall either have the lowest floor, including basement, elevated to one foot above the base flood elevation; or, together with attendant utility and sanitary facilities, shall:

d. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water;

e. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and

f. Be certified by a registered professional engineer or architect that the design and methods of construction in accordance with accepted standards of this subsection based on their development and/or review of the structural design, specifications and plans.

3. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in 7.75.070 H (1).

H. In all areas where base flood elevation data is not available, either through the Flood Insurance Map, the Federal Emergency Management Agency or from another authoritative source, applications shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgement and includes use of historical data, high water marks, photographs of past flooding, etc., where available. All structures shall be elevated at least two feet above grade in these areas.

I. Within areas of designated as floodways on the FIRM maps, encroachments are prohibited.

7.75.080 Application submission requirements.

A. All applications for development in the Flood Hazard Overlay shall be accompanied by:

1. A registered professional engineer's certification that the proposed project will not cause a rise in base flood elevation during a one hundred-year event as it exists on the FIRM Flood Insurance Rate Map effective August 16, 1988 or create additions that would be detrimental to adjacent or neighboring properties.

2. Three copies of the development plan(s) and necessary data or narrative which explains how the development conforms to the standards. Sheet size for three sets of the development plan(s) and required drawings shall be eighteen inches by twenty-four inches. The fourth set shall shall be 11" x 17". The scale for all development plans shall be an engineering scale.

B. The development plan and narrative shall include the following information. Items may be combined on one map.

1. Existing site conditions including vicinity map showing the location of the property in relation to adjacent properties and including parcel boundaries, dimensions and gross area;

2. The location, dimensions and names of all existing and platted streets and other public ways, railroad tracks and crossings, and easements on adjacent property and on the site and proposed streets or other public ways, easements on the site;

3. The location, dimensions and setback distances of all existing structures, improvements, utility and drainage facilities on adjoining properties and existing structures, water, sewer, improvements, utility and drainage facilities to remain on the site; and proposed structures, water, sewer, improvements, utility and drainage facilities on the site;

4. Existing contour lines at two-foot intervals for slopes from zero to ten percent and five-foot intervals for slopes over ten percent;

5. The drainage patterns and drainage courses on the site and on adjacent lands;

6. Potential natural hazard areas including:

a. Floodplain areas,

b. Areas having a high seasonal water table within zero to twenty-four inches of the surface for three or more weeks of the year,

c. Unstable ground (areas subject to slumping, earth slides or movement). Where the site is subject to landslides or other potential hazard, a soils and engineering geologic study based on the proposed project may be required which shows the area can be made suitable for the proposed development,

d. Areas having a severe soil erosion potential, and

e. Areas having severe weak foundation soils;

7. Identification information, including the name and address of the owner, developer, and project designer, and the scale and north arrow;

8. A grading and drainage plan at the same scale as the site conditions and including the following:

a. The location and extent to which grading will take place indicating general contour lines, slope ratios, and slope stabilization proposals,

b. A statement from a registered engineer supported by factual data that all drainage facilities are designed in conformance A.P.W.A standards and as reviewed and approved by the public works director.

9. Elevation in relation to mean sea level of the lowest floor (including basement) of all structures and elevation in relation to mean sea level to which the structure has been floodproofed.

7.75.090 Storage, placement or stockpiling buoyant or hazardous materials in flood hazard areas.

A. The transportation of buoyant or hazardous materials from rising floodwaters contributes to the community's flood hazard. Accordingly, the placement, storage or stockpiling of buoyant or hazardous materials in a flood hazard area or floodway is prohibited, except as required for a period not to exceed 30 days during the months of May, June, July, August or September as part of a public works project.

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