Flood Definitions & Standards

The City of Cottage Grove Development Code establishes policy for development within Areas of Special Flood Hazard. (For an entire Flood Damage Prevention Code, see Development Code Chapter 14.37.200.) The following definitions are provided by the Flood Damage Prevention Ordinance as of August 24, 2020.

Accessory Structure means a structure on the same parcel of property as a principal structure, the use of which is incidental to the use of the principal structure.
Appeal means a request for a review of the interpretation of any provision of this ordinance or a request for a variance.
Area of Shallow Flooding means designated Zone AO, AH, AR/AO or AR/AH on a community’s Flood Insurance Rate Map (FIRM) with a one percent or greater annual chance of flooding to an average depth of one to three feet where a clearly defined channel does not exist, where the path of flooding is unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow.
Area of Special Flood Hazard means the land in the floodplain within a community subject to a 1 percent or greater chance of flooding in any given year. It is shown on the Flood Insurance Rate Map (FIRM) as Zone A, AO, AH, A1-30, AE, A99, AR. “Special flood hazard area” is synonymous in meaning and definition with the phrase “area of special flood hazard”.
Base Flood means a flood having a one percent chance of being equaled or exceeded in any given year.
Base Flood Elevation (BFE) means the elevation to which floodwater is anticipated to rise during the base flood.
Basement means any area of the building having its floor subgrade (below ground level) on all sides.
Below-grade Crawlspace means an enclosed area below the Base Flood Elevation in which the interior grade does not exceed 2 feet below the lowest adjacent exterior grade and the height, measured from the interior grade of the crawlspace to the bottom of the lowest horizontal structural member of the lowest floor, does not exceed 4 feet at any point.
Conditional Letter of Map Revision (CLOMR) means a letter from FEMA commenting on whether a proposed project, if built as proposed, would meet the minimum NFIP standards or proposed hydrology changes. If the project, built as proposed, revises the Flood Insurance Rate Map and/or Flood Insurance Study, a LOMR is required to be submitted no later than 6 months after project completion.
Datum means the vertical control datum from which all vertical elevations are determined. Historically, Flood Insurance Rate Maps have used the National Geodetic Vertical Datum of 1929 (NGVD29). The vertical datum currently adopted by the federal government as a basis for measuring heights is the North American Vertical Datum of 1988 (NAVD88). (See Mean Sea Level.)
De Minimis Development means development that is exempt under this code provided impacts of the development are negligible or insignificant. Examples include: paving or hardscaping of flat areas; certain types of fencing per Table 14.37.210; and raised garden beds.
Development means any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment or materials.
Elevated Building means a non-basement building which has its lowest elevated floor raised above ground level by foundation walls, shear walls, post, piers, pilings, or columns.
Encroachment means the activities or construction within the Floodway including, fill, excavation, grading, new construction, substantial improvements and other development.
Essential Facility or Critical Facility means:

i.    Hospitals and other medical facilities having surgery and emergency treatment areas;

ii.   Fire and police stations;

iii. Tanks or other structures containing, housing or supporting water or fire-suppression materials or equipment required for the protection of essential or hazardous facilities or special occupancy structures;

iv. Emergency vehicle shelters and garages;

v.   Structures and equipment in emergency-preparedness centers;

vi. Standby power generating equipment for essential facilities; and

vi. Structures and equipment in government communication centers and other facilities required for emergency response.
Flood or Flooding means:

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

1. The overflow of inland or tidal waters.

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

3. Mudslides (i.e. mudflows) which are proximately caused by flooding as defined in i(2) of this definition and are akin to a river of liquid and flowing mud on the surfaces of normally dry land areas, as when earth is carried by a current of water and deposited along the path of the current.

ii. The collapse or subsidence of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in flooding as defined in paragraph (i)(1) of this definition.
Flood elevation study means an examination, evaluation and determination of flood hazards and, if appropriate, corresponding water surface elevations, or an examination, evaluation and determination of mudslide (i.e., mudflow) and/or flood-related erosion hazards.
Flood Insurance Rate Map (FIRM) means the official map of a community, on which the Federal Insurance Administrator has delineated both the special hazard areas and the risk premium zones applicable to the community. A FIRM that has been made available digitally is called a Digital Flood Insurance Rate Map (DFIRM).
Flood Proofed or Flood Proofing means any combination of structural and nonstructural additions, changes, or adjustments to structures which reduce or eliminate risk of flood damage to real estate or improved real property, water and sanitary facilities, structures, and their contents.
Floodway means 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 a designated height. Also referred to as "Regulatory Floodway."
Functionally dependent use means a use which cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and ship building and ship repair facilities, and does not include long term storage or related manufacturing facilities.
Highest adjacent grade means the highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.
Historic Structure means a structure that is:
1. Listed individually in the National Register of Historic Places (a listing maintained by the U.S. Department of Interior) or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;
2. Certified or preliminarily determined by the Secretary of the Interior as contributing to the historical significance of a registered historic district or to a district preliminarily determined by the Secretary to qualify as a registered historic district;
3. Individually listed on a state inventory of historic places which have been approved by the Secretary of the Interior, or;
4. Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:
  1. By an approved state program as determined by the Secretary of the Interior, or;
  2. Directly by the Secretary of the Interior in states without approved programs.
Letter of Map Change (LOMC) means an official FEMA determination, by letter, to amend or revise effective Flood Insurance Rate Maps and/or Flood Insurance Studies. LOMCs are issued in the following categories:
1. Letter of Map Amendment (LOMA) means an amendment to the FIRM based on technical data showing that an existing structure or parcel of land that has not been elevated by fill (natural grade) was inadvertently included in the special flood hazard area because of an area of naturally high ground above the base flood.
2. Letter of Map Revision (LOMR) is a letter from FEMA stating that an existing structure or parcel of land that has been elevated by fill would not be inundated by the base flood. A LOMR revises the current FIRM and/or FIS to show changes to the floodplains, Floodways or flood elevations. LOMRs are generally based on manmade alterations that affected the hydrologic or hydraulic characteristics of a flooding source and thus result in modification to the existing regulatory Floodway, the effective Base Flood Elevation or the Special Flood Hazard Area. It is recommended that a Conditional Letter of Map Revision be approved by FEMA prior to issuing a permit to start a project that has a potential to affect the special flood hazard area.
Lowest Floor means the lowest floor of 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 is not built so as to render the structure in violation of the applicable non-elevation design requirements of this Chapter.
Manufactured Dwelling or Home means a structure, transportable in one or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when attached to the required utilities. The term "manufactured dwelling" does not include a "recreational vehicle" and is synonymous with “manufactured home”.
Manufactured Dwelling Park or Subdivision means a parcel (or contiguous parcels) of land divided into two or more manufactured dwelling lots for rent or sale.
Mean Sea Level means for purposes of the National Flood Insurance Program, the National Geodetic Vertical Datum (NGVD) of 1929 or other datum, to which Base Flood Elevations shown on a community's Flood Insurance Rate Map are referenced.
New Construction means floodplain management purposes, “new construction” means structures for which the “start of construction” commenced on or after the effective date of a floodplain management regulation adopted by Cottage Grove (November 11, 1985) and includes any subsequent improvements to such structures.
Oregon Specialty Codes means the combined specialty codes adopted under ORS 446.062, 446.185, 447.020 (2), 455.020 (2), 455.496, 455.610, 455.680, 460.085, 460.360, 479.730 (1) or 480.545, but does not include regulations adopted by the State Fire Marshal pursuant to ORS chapter 476 or ORS 479.015 to 479.200 and 479.210 to 479.220. The combined specialty codes are often referred to as building codes.
Recreational Vehicle means a vehicle that is built on a single chassis; is 400 square feet or less when measured at the largest horizontal projection; is designed to be self-propelled or permanently towed by a light duty truck; and designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel, or seasonal use.
Special Flood Hazard Area: See “Area of Special Flood Hazard” for this definition.
Start of Construction includes substantial improvement and means the date the building permit was issued, provided the actual start of construction, repair, reconstruction, 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 stage 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 foundations 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. For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor or other structural part of a building whether or not the alteration affects the external dimensions of a building.
Structure means for floodplain management purposes, a walled and roofed building, including a gas or liquid storage tank, which is principally above ground, as well as a manufactured dwelling.
Substantial Damage means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed 49 percent of the market value of the structure before the damage occurred.
Substantial improvement means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 49 percent of the market value of the structure before the "start of construction" of the improvement. This term includes structures which have incurred "substantial damage," regardless of the actual repair work performed. The term does not, however, include any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions.
Variance means a grant of relief by the City of Cottage Grove from the terms of a flood plain management regulation.
Violation means the failure of a structure or other development to be fully compliant with the community’s flood plain management regulations. A structure or other development without the elevation certificate, other certifications or other evidence of compliance of this Chapter is presumed to be in violation until such time as that documentation is provided.
Water Surface Elevation means the height, in relation to a specific datum, of floods of various magnitudes and frequencies in the flood plains of coastal or riverine areas.

Flood Definitions & Standards

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