Regulatory Floodplain District (RFD)
Section 131. Regulatory Floodplain District - RFD.
(1) Purpose. The Regulatory Floodplain District is established for the following purposes:
(a) To reduce the potential danger and serious damage to life and property due to flooding;
(b) To control the alteration of, encroachment into and use of areas subject to flooding; and
(c) To reduce the financial burden imposed on the community as a result of flood damage.
(a) “Base Flood” – a flood that has a one percent chance of occurrence in any single year, as established by the Federal Emergency Management Agency (FEMA) data or the best available information. Also referred to as the “100-year flood”. (Added by Ord. No. 5523/6-05).
(b) “Base Flood Elevation” – the limits of the base flood are delineated by the City Engineer as identified on the most current National Flood Insurance Rate Maps (FIRM), and the Flood Insurance Study for the City of Hillsboro and for Washington County . (Added by Ord. No. 5523/6-05).
(c) “Channel” or “Watercourse ” - a natural or artificial depression of perceptible extent, with definite bed and banks to confine and conduct flowing water either continuously or periodically. (Amended by Ord. No. 3308/4-82).
(d) “Elevated Structure” - A structure constructed over the floodplain either on a permanent foundation or pilings to elevate the lowest floor above the base flood elevation. (Amended by Ord. No. 3308/4-82 and by Ord. No. 5523/6-05).
(e) “Fill” - any act by which earth, sand, gravel, rock, structures, or any similar material is deposited, erected, placed, pulled, or transported, including the conditions resulting there from, within the limits of the floodplain. (Amended by Ord. No. 3308/4-82).
(f) “Flood” - a temporary rise in stream flow or stage that results in inundation of the areas adjacent to the channel. (Amended by Ord. No. 3308/4-82).
(g) “Flood Fringe ” - that portion of the floodplain not contained in the floodway. (Amended by Ord. No. 3308/4-82).
(h) “Flood Insurance Rate Map (FIRM)” – means 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.
(i) “Flood Insurance Study (FIS)” – the official report provided by the Federal Insurance Administration that includes flood profiles, the Flood Boundary-Floodway Map, and the water surface elevation of the base flood. (Added by Ord. No. 5523/6-05).
(j) “Floodplain” - the flood hazard area adjoining a channel or watercourse that is subject to inundation by regional flood including both the floodway and flood fringe. (Amended by Ord. No. 3308/4-82).
(k) "Floodproofed Structure" - Any structure, together with its attendant utilities and sanitary facilities, which has been certified by a registered professional engineer or architect as having met the following criteria:
1) Below the 100-year Flood level, the structure is watertight, with walls substantially impermeable to the passage of water; and
2) The structure is built of structural components capable of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy; and
3) The design and construction methods of the structure shall be in accordance with accepted standards for meeting Section 131 (2)(k)(1), and 131 (2)(k)(2).
A record of such certification indicating specific elevations to which the structures are floodproofed shall be maintained with the Building Department of the City of Hillsboro.
(Amended by Ord. Nos. 3308/4-82; and 3707/6-87).
(l) “Floodway” – a channel or watercourse and the adjacent land areas that must be reserved in order to discharge the 100-Year flood without cumulatively increasing the water surface elevation more than one foot. The elevation and location of the floodway is identified on the most current National Flood Insurance Program Flood Boundary, Flood Insurance Study and Floodway Map for the City of Hillsboro, and for Washington County. (Added by Ord. No. 3308/4-82; Amended by Ord. No. 3707/6-87 and by Ord. No. 5523/6-05).
(m) “Lowest Floor” – is 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. (Added by Ord. No. 5523/6-05).
(n) "Structure" - For the purposes of Section 131 only, the definition of structure contained in Section 3 (84) of this Ordinance, No. 1945, includes manufactured homes used for residential, commercial, or industrial purposes. (Added by Ord. No. 3707/6-87; Amended by Ord. No. 5523/6-05).
(o) “Substantial Damage” – A structure has been substantially damaged if the cost of repairing the structure to its condition before the damage occurred equals or exceeds 50 percent of the market value of the structure prior to the damage. (Added by Ord. No. 5523/6-05).
(p) “Substantial Improvement” – means any repair, reconstruction, or improvement of an existing 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:
1) 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; or
2) Any alteration of a structure listed on the National Register of Historic Places or a State Inventory of Historic Places.
(Added by Ord. No. 5523/6-05)
(Subsection (2) Amended by Ord. No. 5523/6-05).
(3) Establishment of Regulatory Floodplain District (RFD)
(a) A Regulatory Floodplain District (RFD) is hereby created as a superimposed zone applied over existing zones, the boundaries of which encompass the Floodplain.
(b) Where provisions of this Section conflict with those of the underlying zone, the more restrictive provisions shall prevail.
(c) The areas of special flood hazard identified by the Federal Insurance Administration in a scientific and engineering report entitled “The Flood Insurance Study” for the City of Hillsboro, with accompanying Flood Insurance Rate Maps are hereby adopted by reference and declared to be a part of this ordinance. The City Engineer shall make interpretations where needed, as to exact location of the boundaries of the areas of special flood hazards (for example, where there appears to be a conflict between a mapped boundary and actual field conditions). The person contesting the location of the boundary shall be given a reasonable opportunity to appeal the interpretation. Any appeal of the City Engineer's interpretation under this section shall be made to the City Manager or the Manager's designee. (Added by Ord. No. 5523/6-05).
No structure, whether public or private, shall hereafter be located, extended, converted, expanded, enlarged, replaced, or structurally altered, and no change or alteration of use of land, public or private, and no encroachment or fill shall take place within the boundaries of the RFD without full compliance with the terms of this Ordinance.
(5) Uses Permitted Outright in Regulatory Floodplain District .
The following open space, utility, transportation, and environmental mitigation uses shall be permitted in the RFD to the extent that they are not prohibited by the provisions of any underlying zone. These uses shall be in compliance with applicable Federal, State, and local requirements, and shall not include any topographic alterations or encroachments. Uses permitted outright in the RFD shall be approved only upon certification by a registered professional civil engineer demonstrating that the alterations satisfy a no-rise analysis and will not reduce the capacity of the site to carry the base flood, or cause any increase in the base flood level: (Amended by Ord. No. 4642/1-98 and by Ord. No. 5523/6-05).
(a) Agricultural use, except for the raising of livestock, that is conducted without a structure other than a boundary fence; (Amended by Ord. No. 3294/1-82.)
(b) Temporary structures that will be removed during the period of flood risk;
(c) Recreational uses requiring only minor structures such as picnic tables and barbecues, which are firmly anchored and built of flood-resistant materials; (Amended by Ord. No. 3707/6-87.)
(d) Residential uses that do not contain buildings;
(e) Underground utility facilities adequately protected from water damage; and constructed to minimize infiltration by flood waters; (Amended by Ord. No. 3707/6-87.)
(f) Repair, reconstruction, or improvements of an existing structure, the cost of which is less than 50 percent of the market value of the structure prior to the improvement or damage requiring reconstruction. Such repairs, reconstruction, or improvements shall be constructed to minimize flood damage, by using flood-resistant materials, anchoring, and the protection of on-site public and private utilities where applicable. (Amended by Ord. Nos. 3308/4-82; and 3707/6-87.)
(g) Repair, reconstruction, or improvements of an existing structure including repair or replacement of underground water and/or sanitary systems necessary to correct existing code violations that cause unsafe living conditions or for any alteration of a structure listed on the National Register of Historic Places or a State Inventory of Historic Places. (Added by Ord. No. 5523/6-05).
(h) Public roadways, light rail transit tracks and associated bridges and crossings, bikeways, and footpaths, needed to implement Section 13 of the Transportation element of the Hillsboro Comprehensive Plan Ordinance No. 2793. Any construction, reconstruction, or repair of public roads, light rail transit tracks and associated bridges and crossings, bikeways, or footpaths shall require the approval of the City Engineer to assure compliance with the intent of this Ordinance. Said public roadway, light rail transit tracks and associated bridges and crossings shall have their travel surfaces elevated one foot above the elevation of the 100 year floodplain. (Added by Ord. No. 3460-A/5-84; and Amended by Ord. No. 4300/12-94.)
(i) Wetland or floodplain mitigation, restoration, or other enhancement that does not reduce floodplain carrying capacity, reduce floodplain storage capacity, or raise floodwater elevations. Mitigation and enhancement projects may be exempt from the provisions of Sections 131 (7) (b) and 131 (7) (c) (1) through (7) (c) (4), and (7) (c) (10), but shall comply with the provisions of Sections 131 (7) (c) (5) through (7) (c) (9). Mitigation and enhancement are also subject to review by the Oregon Division of State Lands and the US Army Corps of Engineers. (Added by Ord. No. 4642/1-98).
(Subsection (5) Amended by Ord. No. 5523/6-05).
(6) Uses Requiring Special Use Approval
The following uses may be permitted upon approval of the Planning Commission. The procedure for permitting these uses shall be the same as provided for in Sections 78 - 83, except the matter will be heard before the Planning Commission:
(a) Any roadway, excepting those roadways defined by Section 131 (5) (g), airport runway, dock, pier, and parking spaces not otherwise required by this Ordinance.
(b) Above-ground utility structures, only if constructed and installed to minimize flood damage and infiltration by flood waters;
(c) Storage of material or equipment that shall be either not subject to damage by a flood, or readily removable. If not readily removable, the material or equipment shall be anchored to prevent flotation resulting in damage to other structures or obstruction of the water flow;
(d) Recreation vehicle parks or camping areas shall be occupied fewer than 180 consecutive days, and not during the period of flood risk. Recreational vehicles placed on sites within Zones A1-30, AH, and AE on Hillsboro's FIRM must be fully licensed and ready for highway use, on wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached additions. All on-site improvements which are not to be removed during periods of flood risk shall be constructed to minimize flood damage in accordance with Section 131 (5)(c) and (5)(e); (Amended by Ord. No. 5523/6-05).
(e) Alteration of the topography, including cuts and fills, grading, paving, mining, dredging, drilling, or other similar operations.
(f) Elevated structure;
(g) Floodproofed structure;
(h) Recreational uses not included in Subsection (5)(e);
(i) Accessory structure or use not subject to flood damage;
(j) Radio transmission facilities;
(k) Raising of livestock;
(I) (Deleted by Ord. No. 5523/6-05).
(m) Reconstruction or improvements of an existing structure, including repair or replacement of private underground water and/or sanitary systems, to that structure, that has incurred substantial damage where damage of any origin was sustained by a structure whereby the cost of restoring the structure to it's before damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred. (Added by Ord. No. 5523/6-05).
(Subsection (6) Amended by Ord. No. 3707/6-87 and by Ord. No. 5523/6-05).
(7) Standards Governing Special Use Approvals in the Regulatory Floodplain District
A special use approval in the RFD shall comply with the Hillsboro Comprehensive Plan, with other applicable Federal, State and local requirements, and with the following:
(a) Those standards contained in Section 83;
(b) No encroachment, alteration, filling, construction of structures, or other similar activities shall be allowed in the floodway, with the exception of: (Amended by Ord. No. 5523/6-05).
1. those activities allowed outright in Section 131(5) , and
2. with the addition of above-ground utility structures as cited in Section 131 (6)(b) and (7)(e); bridges, and those activities intended for erosion control where:
a) Certification by a registered professional civil engineer is provided demonstrating that a no-rise analysis was completed and that the proposed activity shall not result in any increase in flood levels during the occurrence of the base flood,
b) If 2. a) is satisfied, then all applicable provisions of the RFD shall be met.
(c) Alteration of the topography, including cuts and fills, grading, paving, mining, dredging, drilling, or other similar operations in the flood fringe only if:
(1) No more than 30% of the lot area of the subject parcel(s) within the floodplain is impacted by fill, alteration or encroachment. (Amended by Ord. No. 4695/8-98.)
(2) All cuts and fills are made to a depth not to exceed 5 feet or made to a depth commensurate with the surrounding topography;
(3) There is no alteration of the topography below the lowest pre-existing elevation on the property;
(4) No impoundment of water occurs except in conjunction with the uses allowed in Section 131(5) and (6);
(5) All resultant slopes created by alteration of the topography are no greater than 20%;
(6) All impacted areas are stabilized from erosion with vegetation;
(7) All construction activity and stabilization be accomplished between May 1st and September 1st of the same year or as approved by the City Engineer;
(8) All fills are balanced by corresponding cuts so that the on-site storage capacity of the floodplain is retained;
(9) All cut and fill activity is conducted so as to avoid disturbing the topography or vegetation of floodplain areas adjacent to the alteration. Adjacent floodplain areas disturbed during cut and fill activity shall be restored to their natural state in accordance with the standards of Section 131 (7); and
(10) All other standards of Section 131 (7) are met.
(d) Elevated residential, commercial, and industrial structure, only if: (Amended by Ord. No. 5523/6-05)
(1) The lowest floor including the basement is at least one foot above the base flood elevation;
(2) Each unit directly accesses to and abuts land which is above the base flood elevation;
(3) All parking spaces required by this ordinance are above the base flood elevation;
(4) All construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage, using methods and practices that minimize flood damage.
(5) All new utility systems serving the structure are designed, elevated, or located to prevent floodwater from entering;
(6) All new water and sanitary sewer systems are designed and constructed to minimize flood damage and infiltration;
(7) On-site private waste disposal systems are located above the base flood elevation; (Added by Ord. No. 5523/6-05)
(8) The structure includes no fully enclosed areas below the elevation of the base flood which are not designed to allow the entry and exit of floodwater. Designs for meeting this requirement must be either certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:
(a) a minimum of two openings shall be provided, having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding; and
(b) the bottom of all openings shall be no higher than one foot above grade; and
(c) any screens, louvers, or other devices or coverings on the openings shall permit the automatic entry and exit of flood waters.
(9) The structure is firmly anchored, to prevent flotation, collapse and lateral movement;
(10) The use will not result in any increase in flood levels during the Base Flood;
(11) All other standards of Section 131(7) are met;
(12) Rebuilt residential uses shall be exempt from Section 131(7)(d)(2) and Section 131 (7)(d)(3)
(13) Crawlspace areas constructed under the building shall comply with the FEMA and Federal Insurance and Mitigation Administration guidelines as specified in the NFIP. (Added by Ord. No. 5523/6-05)
(e) Flood-proofed commercial and industrial structures only if:
(1) The structure and all associated utility systems, are floodproofed below an elevation 1' above the base flood elevation; (Amended by Ord. No. 5523/6-05)
(2) All construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage, using methods and practices that minimize flood damage.
(3) All utility systems serving the structure are designed, elevated, or located to prevent floodwater from entering;
(4) All water and sanitary sewer systems are designed and constructed to minimize flood damage and infiltration;
(5) The structure is firmly anchored to prevent flotation and lateral movement;
(6) The use will not result in any increase in flood levels during the Base Flood;
(7) Prior to issuance of a certificate of occupancy a FEMA Flood Proofing Certificate filed with the Building Department, the property insurer, and the building owner; and (Added by Ord. No. 5523/6-05)
(8) All other standards of Section 131(7) (a) and (b) are met. (Amended by Ord. No. 5523/6-05).
(f) Accessory structure or use only if:
(1) The structure is not used for human habitation;
(2) The structure is designed to have low flood damage potential;
(3) The structure is constructed and placed on the site so as to offer the minimum resistance to the flow of flood waters;
(4) The structure is firmly anchored to prevent flotation and lateral movement;
(5) Service facilities such as electrical and heating equipment shall be elevated or floodproofed;
(6) The use will not result in any increase in flood levels during the Base Flood.
(g) Raising of livestock only if:
(1) the subject property is adjacent to the Regional Urban Growth Boundary;
(2) the number of animals proposed does not exceed the carrying capacity of the floodplain area involved;
(3) a minimum of one acre is available and included for the use;
(4) the livestock is of a grazing variety, including, but not limited to, horses, cows, sheep, and swine;
(5) the use be carried out only during the dry season, usually between May 1 and October 1 of the calendar year, but subject to modification upon review of the Planning Director or as approved during the hearing process;
(6) all other applicable standards of Section 131 (7) are met.
(Subsection 7. Amended by Ord. No. 3707/6-87 and by Ord. No. 5523/6-05).
(8) Additional standards as required
(a) All new development proposals located within floodplain areas in the City shall identify in the application the Base Flood elevation, as established by the most current National Flood Insurance Rate Maps or the best available information for the City of Hillsboro, and for Washington County. If the Base Flood elevation is not available, it shall be provided to the City, by a registered professional engineer, architect, or land surveyor, for any development which is one (1) acre or 10 lots (whichever is less). No lot shall be created below the Base Flood elevation without first complying with the appropriate sections of this ordinance. When reviewing applications for development located in floodplain areas of the City, the Planning Commission shall consider the following additional criteria: (Amended by Ord. No. 5523/6-05).
(1) Consistency of the proposal with the need to minimize flood damage;
(2) Location and construction of public utilities and facilities such as sanitary sewer, natural gas, electrical and water systems, in a manner which minimizes flood damage;
(3) Provision of adequate storm drainage to reduce exposure to flood damage.
(b) The City Engineer shall verify the flood elevation on any floodplain land prior to the issuance of a building permit. A registered professional engineer, architect, or land surveyor shall further certify the specific as-built elevation of the finished floor, and that the finished floor is one foot above base flood level unless floodproofed. The record of such certifications and elevation verification shall be recorded on permanent record with the Planning Department of the City of Hillsboro. (Amended by Ord. No. 5523/6-05)
(c) The City shall obtain, review, and reasonably utilize any base flood elevation and floodway data available from a Federal, State, or other source, in order to administer Section 133.
(d) The City Building Official shall review all building permits to assure that the proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet above grade in these zones may result in higher insurance rates.
(e) Prior to issuance of final occupancy certificates floodproofed commercial and industrial structures built pursuant to Section 131(7)(e) shall have on file with the Planning Department a completed FEMA Floodproofing Certificate (FEMA form 81-65). (Added by Ord. No. 5523/6-05).
(f) The City shall notify Washington County , DLCD, Corps of Engineers, Clean Water Services, Department of State Lands and any other adjacent jurisdictions prior to any alteration or relocation of a watercourse within the City, and shall submit evidence of such notification to the Federal Insurance Administration. (Amended by Ord. No.5523/6-05).
(1) Watercourse alterations or relocations must be approved by the City Engineer prior to construction.
(2) Altered or relocated watercourses must be maintained so that the flood-carrying capacity of the watercourse is not diminished.
(Section 8 Amended by Ord. No. 3707/6-87and by Ord. No. 5523/6-05).
(Section 131 Added by Ord. No. 3123/7-80).