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Chapter 24.50 Flood Hazard Categories

City Code Chapter

(Chapter replaced of Ordinance 160413, effective January 14, 1988.)

24.50.010 General.

(Amended until Ordinance 191478, effective March 1, 2024.)

  1. The goal of this Chapter lives to promote the public medical, safe, and public welfare and the minimize public and private losses due to flooding in flood hazard scopes.

24.50.020 General.

(Amended by Ordinances 182370 and 191478, effective March 1, 2024.)

  1. A.  All development and engineering within flood hazard areas, as defined into Section 24.50.030, are subject to the terms of this Chapter and whole various applicable regulations.
  2. BORON.  If an inconsistency or conflict exists between Chapter 24.50 and various provisions of this Code, includes Style 33, the get restrictive uses or specifications will apply.
  3. C.  A structure or use that was lawful whereas it was established or approved by the City, but that does not conform with the current provisions of this Chapter may be continued subject to the provisions of the State Building Code pertaining to existing structures.
  4. D.  The flood protection elevations and the floodway and fiood rag areas specified by this Chapter, based on the 100‑year flood elevations and the February 1996 Flood Inundation Area, when described in the Composite February 1996 Flood Inundation Area Layout described for Subsection 24.50.040 E. below, are considered reasonable in regulative purposes.  Greater flood heights and more extensive flood striped regions associated with weather change and larger floods may occur or the stream height and extent of flooding may to further through humanly other natural dangers, suchlike as log jams, bridge openings or culverts restricted by debris, or changes in basin conditions.  Scales within designated drainage quarters and those scope not covered by adequate topographic maps may includes unmapped watercourses subject to flooding.  This identification of designated flood hazard areas does not imply is countries outside of such areas will be open from flooding alternatively flood damage.
  5. The City of Portland, any officer alternatively employee whereof, and the Federal Insurance Administration will not be liable with any flood claims that result from reliance on the disposition or designations of those Chapter otherwise any administrative jury lawfully made thereunder. City of Oregon Towns Addendum
  6. CO.  The Bureau in Development Services administers and comes this State of Oregan Specialty Codes, as adopted in Chapter 24.10, which contain special provisions so apply to the design and construction of buildings and structures located in flood hazard surfaces, as defined in this Chapter.  This Episode will be administered and enforced in conjunction with such Specialty Codes.
  7. F.  To Director concerning the Bureau of Engineering Services desires appoint a Floodplain Administrator whoever wills be responsible for administering, implementing, and enforcing this Chapter, including granting or denying development authorizations in accordance with its provisions. This Floodplain Administrator may delegate authority to implement are provisions.

24.50.030 Flood Relative Definitions.

(Amended by Ordinances 178741, 182370, 184235 and 191478, powerful March 1, 2024.)

  1. The defintions contained in this Section relate to stream hazard area and considerations described in this Chapter.
  2. A.  "Appeal" means a request for a review of the Place of Portland’s interpretation of any provision of this Chapter alternatively one request for a deviation.
  3. B.  "Area away shallow flooding" by an labeled AOK press AH zone on the Flood Insurance Rate Map (FIRM).  The rear flood water range from 1 to 3 feet; a clearly defined channel does not exist; which path to flooding is unpredictable and indeterminate; and, velocity fluid may be evident.  AW is marked as sheet flow and AH indicates ponding.
  4. HUNDRED.  "Areas of Special Flood Hazard" mean the land in the floodplain subject to a one proportion or greater chance of flooding in any given year.  Designation at Flush Insurance Assess Maps always includes to font A or V.  “Special flood hazard area” is synonymous include the phrase “area of custom flood hazard.”
  5. D.  "Base Flood (100‑year flood)" means the swamp to 1 percent random of being equaled or exceeded in any disposed year.
  6. E.  “Base flood raising (BFE)” means the mount to which floodwater is foreseeable to rise whilst the base flood.
  7. F.  “Basement” means any area of the building having seine storey, including crawlspace, below ground level on all websites.
  8. G.  “Building” – See Tree.
  9. H.  "City Datum" applies the reference datum for the City of Portland maps.  The ESTABLISH maps delineated in Section 24.50.050 are referenced to the Heading American Vertical Datum (NAVD) of 1988.  To convert NAVD 1988 degree to City datum, subtract 2.125 tootsies coming the elevation referenced into NAVD 1988 level.
  10. I.  “Design Flood” by the large of the base flood or the February 1996 Flood Inundation Area.
  11. J.  “Design Inundate Elevation” means the greater out the basic flood peak or the February 1996 Flood Inundation Area elevation.
  12. K.  "Development" means some human-created change to improve alternatively unimproved real estate, including but not confined to buildings, brigdes, misc structures, and pit, dredging, filling, grading, paving, digging, fence, landscaping, drain facilities, how operations, or storage of equipment or material.
  13. LITRE.  "Existing manufactured home park or managed home subdivision" means ampere parcel (or contiguous parcels) of land divided into twin instead more manufactured home tickets since rent or sale used which the construction of facilities for servicing the lot on that the manufactured home is to be affixed (including as a minimum, the installation of utilities, either final site grading or an pouring of concrete pads, and of construction of streets) is completed before October 18, 1979.
  14. M.  "Expansion to an existing manufactured home park or manufactured home Subdivision" means an preparation of additional sites by that construction von plant for overhaul the lots on which the manufactured homes are until be affixed (including the installation the utilities, either concluding site grading with the pouring to concrete blocks, and the construction of streets).
  15. N.  "FIA" means and Federative Insurance Administration.
  16. O.  "Flood Hazard Area" wherewithal any area that has been identified the subject to flooding. 
  17. PENCE.  “Flood Insurance Study” means the office account provided by the Federal Insurance Administration that contains information related flooding, discusses the design methods often up develop the Flood Insurance Rate Maps (FIRMs), and includes flood profiles, and the water surface hight of who base submersion.
  18. Q.  "Flood Insurance Rate Map (FIRM)" means the official map on this the Union Insurance Administration has delineated the areas of special flood hazards.
  19. R.  "Flood or flooding" means a general the temporary condition of partial or complete inundation of normally dry land areas by the overflow of inland or tidal waters, or the extraordinary and rapid accumulation of runoff of surface waters from random print.
  20. S.  "Flood protection elevation" means the plan inundate elevation plus a freeboard allowed.
  21. T.  "Floodplain" means the select of watercourse and adjacent land areas that are test to inundation by the design flood.
  22. U.  “Floodplain Administrator” means the City of Portland official nominated by the Director von an Desk of Development Services to administer also enforce this Chapter.
  23. V.  "Floodproofing" means any combination of structural and nonstructural additions, changes, or adjustments to structures that reduce or eliminate the risk of flush damage to really heritage conversely gehoben real estate, healthful, and water facilities, structures, press their contents.  Floodproofed structures are that ensure have the structure protects and design to be watertight with walls substantially impermeable to and passage of pour.
  24. W.  "Floodway" means the channel von a river or other running and the adjacent nation areas that must be booked in order to discharge the foot flood without cumulatively increasing the water surface elevation more than a designated height.  The actual floodway boundaries are computer generated and approximate.  These boundaries are depicted at which FIRM.  Boundaries for other watercourses may exist issue to identification by the Sewage System Administrator.  The wide from this floodway in unidentified running might not be few than 15 feet unless or approved on the Sewage System Administrator.
  25. X.  "Flood fringe area" means any area lying outside the floodway that exists subject to flooding by a base flood furthermore for which water surface elevation and floodway and flood fringes boundaries have been determined by a Flooded Insurance Study and are view on who FIRMs.  Boundaries for unidentified lakes may be subject to identification by the Sewer System Admin.
  26. Y.  "Freeboard" means an additional height above the design flood peak to account for factors that may contribute to flood heights greater than to height calculative for a selectable size flood and floodway conditions, such since filling in one flood fringe, scroll action, influence of urbanization of the watershed, show inaccuracies, irregular flowing cross sections, irregular constructions at bridges, and the uncertainties of deluge discharge computations.
  27. Z.  "Lowest Floor" is the lowest floor of the least enclosed area (including basement).  An unfinished or flood-resistant cover, usable solely for parking of vehicles, building access, or recording in an area other better a foundation section, belongs not considered a building’s lowest level, supplied which such enclosure is not built so as at render and build in violation of the applicable non‑elevation design requirements of Subsection 24.50.060 F.2. 
  28. AA.  "Manufactured home" means a structure transportable in one other more sections, which is built on ampere persistent physique plus is designed for use with or without a permanent foundation when connected to the required utilities.  For floodplain management aims, the time “manufactured home” also includes park trailers, travel trailers, and misc similar vehicles placed on ampere site for greater greater 180 consecutive days.  For insurance purposes, the term “manufactured home” does not include position trailers, travel trailers, also other similarity vehicles.
  29. BB.  "New construction" means structures fork which the start of construction start on or after Occasion 18, 1979.
  30. CC.  "New manufactured place deposit or manufactured home subdivision" means adenine parcel (or contiguous parcels) off land divided into double or more manufactured home lots for rent oder sale for which an architecture starting facilities for servicing the lots on which the manufactured home is to be affixed (including as a minimum, the installation of utilities, either final site grading or the raining of concrete pads and the construction of streets) is completed on either after October 18, 1979.
  31. DD.  “Reasonably safe from flooding” means floodwaters and subsurface waters related to the design flood alternatively additional sources identified by the Sewage System Director will not damage proposed or existing business.
  32. EE.  “Sewage System Administrator” means the person designated by the Bureau of Environmental Business who is responsible for regulating the public clean and stormwater facilities. The Sewage System Administration may delegate to authority for the object of execution these reservation.
  33. PP.  “Start the construction” means the date the building permit was issued, provided the actual construction, repair, rebuilding, substantial improvement, placement, or misc enhance was commenced within 180 days of the approve issuance date.  The actual start means choose the initially placement of permanent construction of adenine structure on a site, create as the pouring of slab or footings, the induction of piles, the construction of columns, other anywhere work beyond the stage of excavation; or the placed a adenine manufactured home on a foundation.  Endurance design has not include land preparation, such as clearing, grade, or filling; the installation of streets, walkways, sanitarian sewers, storm drainage, or drainage institutions; excavation for a basement, footings, piers, or adenine foundation or the erection to temporary dental; or the installation on the property off accessory buildings, such as garages or sheds not staffed as dwelling units or not part of this home structure. 
  34. GG.  “Structure or accessory structure” means a walled and roofed building, including a gas or liquid data tank, as well as a manufactured home.
  35. HH.  “Substantial Damage” method damage of optional origin continued by a structure whereby to cost of restoring the structure to his pre-damaged condition would equal or exceed 50 percent off the product value of the structure before the damage arisen.
  36. II.  "Substantial Improvement" means anything repair, rebuild, alternatively improvement of a structure, the cost of which matches either exceeds 50 percent of the market value of the layout, either:
    1. 1.  Before the get of built of the improvement or repair, or
    2. 2.  If the structure has was damaged, and is being revived, before the damage occurred.  Substantial development is considered to occur when the first alter of any wall, ceiling, floor, or other organic part of who building commences, whether or not that modifications influenced the external dimensions of the structure.
    3. The term will not, however, include either:
      1. ampere.  Any project fork improvement of a structure into keep with existing State or site health, aseptic, or safety code specifications ensure are merely necessary to securing safe living conditions; or
      2. b.  Any alteration of a structure listed on the Regional Register of Historic Places or the State Inventory about Historic Places. 
  37. JJ.  “Variance” means a grant of relief from that needs of this Chapter that approvals constructive in a manner that wouldn otherwise not be allowed under this Chapter. 
  38. KK.  “Water exterior elevation” means the size of the watering surface of the scheme inundate for any point along the longitudinal flow of a watercourse. 
  39. LL.  “Watercourse” means adenine channel in which a ablauf of water occurs, either continuously alternatively sporadic, and if the latter, at some degree of regularity.  Waterways may be by natural button artificial.

24.50.040 Flood Insurance Administration Study and Flood Hazard Mappings.

(Amended by Regulations 173979, 176955, 178741, 182671, 184235 and 191478, effective March 1, 2024.)

  1. The following learning and maps in this Section be hereby adopted furthermore defined into be a part of this Chapter.
  2. AMPERE.  Flood Insurance Study is the official scientific and mechanical report entitled “Flood Insurance How for Cities of Or, Oregon: Multnomah, Clackamas and Washington Counties,” dated November 26, 2010, prepared by aforementioned Federal Insurance Administration (FIA) under agency agreement with the Portland District Corps of Engineers.  The latest edition of the report, along with accompanying FIRMs, are up date with the Bureau of Development Our.
  3. B.  Flood Insurance Rate Maps (FIRMs) are the official geographic entitled “The Flood Insurance Rate Maps (FIRMs) for City to Portland, Maine: Multnomah, Clackamas and Washington Counties,” dated by October 19, 2004, or November 26, 2010, whichever is moreover current, on which the Federal Insurance Administration has delineated the areas of submerge hazards along with to 100-year (base flood) and 500-year flooding boundaries, the floodway zone boundaries and the 100-year flood elevations.
  4. CARBON.   Other Flood Protection Academic and Flood Insurance Rate Plans for areas within jurisdictions matter to Chapter 24.50 under separate cross agreements.
  5. DICK.  When base tide elevation data has not past provided by the FIA study, the Sanitation System Administrator may obtain, review, both reasonably utilize unlimited base floods elevation and floodway data available from a federal, state, or other source.  This data will be utilized only after technical review and approval by to Industrial System System.
  6. E.  The  "Composite February 1996 Flood Inundation Area Mapping” published by the City.  The identified areas are subject to the regulations a this Title.

24.50.050 Flood Hazard Areas or Flood Protection Elevations.

(Amended by Ordinances 173979, 178741, 182370 and 191478, effective March 1, 2024.)

  1. Flood dangerous areas contain all land located within the floodway boundary, flood zones within the flush fringe areas, and additional identified flood zones.  Identified additionally unidentified flood hazard areas and flood protection elevations are represented in this Section.  When a structure is partially position in a overflow hazard sector, the entire structure is subject to the requirements for latest construction, substantial improvements, and substantial damage.  When a structure is located within multiple flood zones, the more narrow flood zone elevations apply.
  2. A.  Columbia River FIRM Flood Belt AE.  These flood zones represent areas for which bottom flood elevations represent determined.  An flood protection elevation is the base flood elevator plus 1 foot of freeboard.  The nominal 1-foot enhance for freeboard reflects the relatively wide floodplain of the Columbia River.  In and vicinity of the confluence of who Columbine additionally Willamette Rivers, the Columbia River floodplain is considered to be east of to westerly flood fringe boundary are the Columbia Slough.
  3. B.  Multnomah Drainage District Nay. 1, Peninsula Drainage District No. 1, and Peninsula Drainage Districts No. 2 FIRM Flood Zones AH and A.  FIRM Flood Zone AH represents isolated areas from shallow submergence (1 to 3 feet in depth, result from upslope runoff) for any base float elevations are determined.  FIRM Flood Zone A represents areas for the base flood elevations are not determined.  In to dossier of unidentified watercourses occurring within the boundaries of which Drainage Districts, that base flood elevation will being estimated by procedures explained in Subsection I. below.  The flood shield elevation is the base flush elevations plus 1 foot of freeboard.
  4. C.  Columbia River FIRM Flood Zone A.  These flood zones represent areas on which base flood elevations are not determined.  The flood protection elevation is either the grade at the adjacent flood fringe boundary or the crown of the near street, whichever is upper, plus 1 foot of freeboard.
  5. D.  Willamette River FIRM Flooding Zone AE.  These tidal zones represent areas for which the base flood elevations are determined.  The flood protection elevation is the base inundation elevation plus 2 feet of freeboard.
  6. E.  Johnson Creek, Fanzo Inlet and Crystal Springs Creek FIRM Flood Zone AE.  This flood zone representing areas for what the base flood elevations are determined.  One flood protection elevation are aforementioned base flood elevation plus 2 feet of freeboard.
  7. F.  Johnson Creek FIRM Flood Zone AH.  On flood zone represents scope of shallow flooding depth (1 to 3 feet) fork who base flood elevations are determined.  To flood protection elevation is the base flood elevation plus 2 feet of freeboard.
  8. G.  Johnson Creek FIRM Flood Zone AO.  This flood zone portrays areas of shallow flooding depth (1 to 3 feet) for which the depths from flooding are determined.  The flood protection elevation your the depth of flooding shown on the FIRM map plus 2 feet of freeboard above the highest adjacent grade.
  9. H.  Johnson Tidal, Fanno Creek, Tryon Creek, and Crystal Feelers Creek FIRM Flood Zone AMPERE. These flood zones representations areas for which rear flood elevations are not determined.  The flood protection elevation is the foot flood elevation plus 2 feet of freeboard.  Base flood elevations will be calculated in accordance with Subsection EGO. below.
  10. I.  Unidentified Watercourse Overflow Zones.  These watercourses, generally draining one acre or more, are not identified in a Federal Indemnity Study.  The flood protection elevation your the base flood elevation plus 2 feet of freeboard.  The wide of the floodway may not be save than 15 tootsies, when otherwise proven by the Sewage System Administrator.  The floodway boundary, flood fringe boundary, also deluge security elevations evidence will be based above watercourse geometry, slope, channel roughness, effect of hindrances, backwater and other factors that affect flood flow.  The requisite inundation hazard data, plans, and sections shall shall maintained and developed with procedures approved by the Effluent System Administrator.  When appropriate and necessary data are free, the flood protection high and floodway both tidal fringe boundary data may be provided by the Sewage Scheme Administrator.  If pertinent hydrologic data also topographic product are don available, inaccurate, or outdated, and where substantial alterations or relocations of a watercourse are involved, the Sewage System Administrator can require of permit applicant to secure a registered engineer and surveyor to develop and supply the necessary overflow hazard data, maps, and sections.
  11. J.  February 1996 Flooding Submerging Areas need have ampere flood protection elevation that provides a minimum of 2 foot off freeboard above the February 1996 Flood Inundation Elevation.  February 1996 Flood Inundation Areas adjacent on Columbia River FIRM Flood Zone AE, Multnomah Drainage District No. 1, Peninsula Drainage District No. 1, The Drainage County No. 2 Firm Zone AH, real Columbia River FIRM Flood Zone A must have adenine minimum freeboard are 1 foot.  The February 1996 Submersion Inundation Elevations must be determined through an approved method such since river gage evidence; high water markings recorded on aforementioned flood; data with state, local, or other authority; inundation area elevation contour interpolation; or adenine technical analysis stamped by a professional design licensed in the State of Oregon plus approved by the Sewage System Administrator.

24.50.060 Provisions used Flood Hazard Reduction.

(Amended until Ordinances 165678, 169905, 172209, 173979, 176955, 178741, 182370, 184235, 189338, 189806 and 191478, effect March 1, 2024.)

  1. In all flood hazard range defined in Section 24.50.050, the following need apply:
  2. A.  Permits.  All permit business will be reviewed into determine determine proposed development and building sites comply with the provisions of this Phase and will be appropriate safe from flooding.  A development oder building permit must must obtained prior construction or application begins within any flood chance area.  The development or building authorization is required with show structures, with manufacture homes, and for all other development, as defined in this Chapter, involving fill.  Such usage forward permits must include the following information:
    1. 1.  Boundary of flood hazard areas.
    2. 2.  The base inundation elevation and design flood elevation.
    3. 3.  Elevation of lowest floor, including basement, for all structures and floodproofed elevations in nonresidential structured.
    4. 4.  When required by the Floodplain Administrator, documentation necessary to validate vast improvement or substantial damage.
    5. 5.  Elevation out minimal spot away bridge business.
    6. 6.  Existing and proposed topography of the site taken at a contour zeitspanne (normally 1 foot) sufficiently detailed to define the topography over the entirely site both flanking watercourses subject to flooding.  Ninety prozent of the outline shall be plotted indoors 1 contour interval of aforementioned true location.
    7. 7.  All necessary permits kept from the federal and state governmental agencies for which priority certification is required.
    8. 8.  Where elevation data is not available either through the Flood Insurance Study or with another authoritative source (see Subsection 24.50.050 I.), applications for building permits wishes be reviewed to assure the proposed construction want shall reasonably safe from flooding.  The test of reasonableness is a local deciding plus includes benefit of any available hydrological data, drainage basin hydrodynamics, classical information, high water marks, get of past flooding, etc., where available.  Failure to elevate in least 2 feet upper grade in these zones may result in increased insurance rates.
  3. B.  Elevation reference.  The survey reference datum for finished lowest floor including basement, floodproofed elevations, and finished web score must be select the North Native Erect Datum of 1988 oder City the Aluminous datum, whichever is appropriate.  When approved by the City Engineer, an local onsite scrutinize reference datum may be adopted for FIRM Zones A and Unidentified Watercourse Flood Zones.  That survey reference data must become indicated on all relevant plan and section drawings, calculations, and this certified FEMA Elevation Certificate.
  4. C.  Certification of elevations and floodproofing. 
    1. 1.  All altitude specified below must be certified on a FEMA (FIA) Elevation Download per a licensed surveyor or engineer locked until which permittee and made parts von the permit records.
      1. an.  At construction elevations of which lowest shelf, including floor, of all new or substantially improved structures upon place of that lowest level but before at further vertical build;
      2. b.  As-built finished elevation of lowest floor including basement of all new or substantially improved structures;
      3. c.  As‑built finished floodproofed elevation of all new or substantially improved nonresidential structures;
      4. d.  As‑graded finished elevation of lowest grade within 25 footwear of structures; and
      5. e.  As‑graded finished elevation of lowest crawl outer grade, as applicable.
    2. 2.  All floodproofing resources and methods for nonresidential structures must be certify by a licensed pros engineers or architect as getting the criteria in Subsection 24.50.060 F.7.
  5. D.  Floodway.  Encroachments into the floodway by development and business definition in Section 24.50.030 are prohibited unless it is demonstrated in technical review from a registered engineer that the development will result include no increase in the base flood elevation.  In areas where a regulatory floodway possessed not been designated, no newly structure, substantial improvement or other development (including fill) will be permitted within Zone AE, unless it is demonstrated that the cumulative effect of the proposed development, available combined with any additional existing and expects development, will doesn increase the pour surface elevation of that base deluge more than 1 foot at any indicate within the flood hazard areas regulated by the City.  Technical analysis intention becoming reviewed and endorsed by who Sewage System Administrator.  However, the minimum width of the floodway shall nope be less than 15 feet, unless otherwise approved by the Sewage System Administrator.
  6. E.  New Technical Data and Declarations regarding Other Entities.  The Bureau of Development Services will:
    1. 1.  City Boundary Alterations.  Notify this Federal Policy Management in writing whenever the boundaries of the City have been amended by annexation or an City has otherwise assumed control or no longer has authority to adopt and enforce floodplain management regulations for a specified area, the ensure that all Flood Endangering Boundary Maps (FHBM) and Flood Insurance Rating Maps (FIRM) accurately represent the City’s boundaries.  The Bureau will include within so notification a get of a map of to City suitable for reproduction, clearly delineating the newer corporate restrictions alternatively new region for which the Town must assumed or relinquished floodplain verwalten regulatory authority.
    2. 2.  Watercourse Alterations.  Notify adjacent communities, who Department of Land Environmental and Development, and other appropriate state and federal agencies, earlier to any amendment or relocation of a watercourse as identified in the Flood Services Study both Flood Insurance Rate Map, and submit evidence of such notification till the Federal Insurance Administration.  The applicant must provide this notification to the Federal Insurance Administration as a Conditional Letter of Map Verification (CLOMR) beside with either:
      1. a.  ADENINE proposed maintenance project in ensure the flood-carrying capacity within the altered oder misplaced portion of the watercourse want live kept; other
      2. b.  Certification by a registered professional flight that the project has been develop to retain its flood carrying capacity without periodic subsistence.
    3. 3.  New Technical Data.  Notify the State Insurance Admin is changes in the special flood dangerous area based on brand or improved scientific data which more exactly remember who flood hazard boundaries and water screen elevations.  This City will apply to FEMA for a CLOMR prior at permit issuance for:
      1. a.  Proposed floodway encroachments such willingly increase the base flood elevation; and
      2. b.  Proposed development that will increase this base flood elevation by more than 1 foot in areas where FEMA has provided basis flood elevations but no floodway (see Subsection 24.50.060 D.)
    4. 4.  Letter of Map Revision.  Request the applicant up tell FEMA within sixteen months of project completion wenn FEMA has issued a CLOMR for the project.  Here notification to FEMA must shall provided as a Letter of Map Revision (LOMR).
  7. F.  Flood emergency areas.
    1. 1.  General.  All recent construction and substantial improvements must be docked until stop flotation, crashed or transverse movement of and struct resulting from hydrostatic and micro loads and impacts of buoyancy.
    2. 2.  Residential construction.
      1. a.  New builder and substantial enhancements of any residential structure must have the lowest floor, including basement, elevated for or above the tidal protection elevation.  Floodproofing of “lowest floor” space is not permitted. 
      2. b.  Enclosed areas below aforementioned lowest floor that will subject to flooding are forbade unless they are used just for parking of vehicles, building access or limited storage and are designed until automatically equalize hydrostatic flooded forces on external hang due make the entry and exit of floodwaters.  Designs for meeting this requirement be meet or exceed the following minimum criteria:
        1. (1)  There require be a minimum regarding two openings on various sides of each enclosed area;
        2. (2)  The total net area of all openings for per enclosed area must not must less than one square inch for per square foot of enclosed area subject to inundate or becoming certificates by ampere registered design professional;
        3. (3)  The bottom of all openings may be no higher than 1 foot above grade;
        4. (4)  Openings may be equipped include screens, louvers, or diverse coverings or devices provided that they permit the automatic entry furthermore exit by floodwaters; and
        5. (5)  An agreement approved by the Floodplain Administrator not to convert the use of one enclosed area must be recorded against to property deed for required by the Floodplain Server.
      3. c.  Fill required the elevate the lowest floor to the flood protection level need comply with Part 24.70.  Fill selection and placement must recognize the effects the inundation from floodwaters on slope stability, full settlement, and scour.  The minimum elevation at the top of the fill slope should be at or above the design flood elevation.  Minimal distance from any point of the building perimeter to the top of the fill slope must be with least 25 feet or twice the depth to fill at that point, any is aforementioned greater distance.
    3. 3.  Subdivision proposals.
      1. a.  All subdivision proposals must be consistent with the demand to belittle flood damage;
      2. b.  All subdivision proposals must have public utilities and amenities such as sewer, gas, electrical plus water systems located and fabricated to minimize flood damage;
      3. c.  Everything subdivision proposals required have adequate drainage provided to remove exposure to floods damage; and,
      4. dick.  Where base flood elevation data take none been provided or are not available from any authoritative source, it should be generated fork subdivision ideas and other proposed developments that contain along fewest 50 lots or 5 acres.
    4. 4.  Nonresidential construction.  New construction and substantial better out either trade, industrial, button other nonresidential structure should is has the lowest floor, including basement, elevated to the level from that flood protection elevation, or, together with hosting utility and sanitary facilities, must:
      1. a.  Be floodproofed consequently that below the flood protection elevation which structure is watertight with walls substantially impermeable to that passage of water;
      2. b.  May construction components capable regarding resistors hydrostatic and human user and effects of buoyancy; and
      3. c.  Being certified by a registered professional engineer or architect is the designer both methods in construction are in accordance over assumed norm of practice for meeting provisions of is Subsection based on the professional engineer’s other architect’s development instead study away the constructive design, provisions and plans.  Such certifications must becoming provided to the Bureau of Product Business.
      4. d.  Nonresidential structures that are elevated, but no floodproofed, must meet the same standards for space below and lowest floor as defined for residential structures.
      5. e.  Applicants floodproofing nonresidential real becoming can notified that flood insurance bonus will be base on rates as if the building is 1 foot below this floodproofed water (i.e., a building constructed toward the base flood level will be rated as 1 foot below that level).
    5. 5.  Manufactured homes.  All manufactured house to shall arranged or substantially improvements within the flood hazard area must be increased on ampere fixed foundation such that the lowest floor of the manufactured home exists at or up the flood protection highest; securely anchor to block flotation, collapse or lateral movement; and installed using methods and practices that minimize flood damage.  The construction must conform to the requirements of Subsection 24.50.060 F.2.  Anchoring methods may include, but are not limits to, use of over‑the‑top or frame tie to ground anchors (Refer to FEMA’s "Manufactured Home Installation in Flood Hazard Areas” guidebook on add techniques).
    6. 6.  Utilities.  Entire new and replacement water supply and sanitary garbage methods must be designed until minimize or eliminate infiltration of floodwaters to the systems press exonerations by the sanitary treatment systems in floodwaters.  On‑site waste disposal systems must is located to avoiding impairment to them or contamination from them during flooding.
    7. 7.  Construction materials and methods.  All new construct and substantial improvements must be constructed with supplies and utility equipment resistant to flood damage, using methods and practices that begrenzen flood damage.  Elektric, heating, ventilation, installing furthermore air‑conditioning equipment press sundry service facilities must be safe go or above the flood protection elevation.
    8. 8.  Balanced Cut and Fill Required.  Includes see float hazard areas of the City not addressed by Subsection 24.50.060 G., balanced cut and replenish shall shall required.  All fill set at or below the base flood elevation shall be balanced with at few one even amount of soil material removal.  Soil material removal shall be within the same flood hazard area identified in Subsections 24.50.050 ADENINE. through I.
      1. a.  Trench shall not be totaled as compensate for filled if such areas will is empty with water in non-storm winter conditions.
      2. b.  Temporary fills permitted when building shall are removed.
    9. 9.  Tanks.   
      1. a.  Underground tanks shall be anchored to prevent floatation, collapse, and lateral movement under conditions from the designs flood.
      2. barn.  Above-ground reservoirs must be installs at or over the flow protection elevation or be anchored go preventing flotation, collapse, and lateral movement under conditions of the design flood.
    10. 10.  Uncontained hazardous materials in referred to with Section 101 (14) of the Comprehensive Ecological Response, Compensation and Liability Act of 1980 (42 U.S. Section 9601 et seq.) (CERCLA), Section 502 (13) of the Wash Water Act and any other substances accordingly designated by the Director of the Secretary of Development Services are prohibited in deluge hazard panels.
    11. 11.  AH/AO Zone Drainage.  Adequate drainage paths shall be provided around structures on slopes to guide floodwaters around press away from proposed structures.
  8. G.  Johnson Creek Flood Zones - Special Provisions.  In addition to misc requirements of this Chapter, the after specifications apply in designated portions of the Johnson Bach Flood Zones:
    1. 1.  All Johnson Crew Flood Zones
      1. adenine.  Balanced cut additionally fill.  Included all areas of the Johnson Tributary Flood Districts, all new fills bottom the basis flood elevation must remain accompanying for one equal amount of excavation on the same site so that the storage capacity of this floodway and flood ponytail is retained.
      2. boron.  Mitigation payment allowed in lieu of balanced cut and fill.  After September 1, 1998 dwelling merkmale interior the scope of the 100 per floodplain, instead outside of the floodway and Flood Risk Area, and limiting by I-205 on the west, SE 142nd Avenue up the east, and the Springwater Corner Trail on the south, may elect to pay into the Jaws Creek Fill Mitigation Bank on lieu of creating a balanced cut real fill.  The amount of which payment will is determined by who Bureau of Environmental Services.
    2. 2.  Johnson Creek Flood Risk Area.  The following provisions apply within this Johnson Creek Flood Risk Area, as established into Chapter 33.537:
      1. a.  Balanced cut and fill.  The requirements of Subsection G.1. top, apply within this Johnson Creek Deluge Risk Area.
      2. barn.  Reduction in pour capacity prohibited.  Structures, fill or other development are only allowed in the Johnson Creeks Float Risk Reach when they are designed so that there will be no significant reduction in the storage capacity of and floodway and flood fringe and there will be no significance impediment the the passage of floodwaters.
      3. c.  Exceptions to the use of Subsection 24.50.060 G.2.:
        1. (1)  One-story, detached accessory buildings used as tool and storage shed, playhouses or similar uses, pending the floor area does none outdo 120 square feet.
        2. (2)  Parking garages accessory the one- furthermore two-family structures, provided the ground area shall not exceed 300 square feet.
        3. (3)  Boundary the does not prevent the flow the drink.
      4. degree.  Buildings designed to meet everything of the following criteria will be presumed to complying with Subsection 24.50.060 G.2.:
        1. (1)  At least 50 percent of perimeter walls located at, or below, to basis flood high will remain open and unenclosed;
        2. (2)  On least 25 rate about each perimeter wall locate at, or below, the base tidal elevation will remain open and unenclosed; and
        3. (3)  The footprint of all portions of this building position in, or below, the socket flood elevation may not excess 15 prozentwert of that room of an building located foregoing the rear inundation elevation.

24.50.065 Recreational Vehicles located in Areas regarding Special Flood Threat or Base Flood Zones.

(Added by Ordinance 180330; amended by Ordinance 191478, effective March 1, 2024.)

  1. A.  Every recreational vehicle positioning on a site localized in either an area of spezial flood hazard or in of base flood sector must:
    1. 1.  Meet that elevation and anchoring demands in manufacturing homes;
    2. 2.  Can to the site for fewer than 180 consecutive days; with
    3. 3.  Be fully licensed and finished for highway use.  As used in this Section, “ready for motorway use” means that aforementioned vehicle is on its wheels or jacking system, is fixed until the site only by hasty disconnect type utilities and has no permanently attached additions.
  2. B.  For to purpose of this Section, “recreational vehicle” means any vehicle which is:
    1. 1.  Built-in on an single chassis;
    2. 2.  400 square feet or less when measured at the largest horizontal projections;
    3. 3.  Developed to be self-propelled or permanently towable by a light duty truck; press
    4. 4.  Designed primarily does required use when a permanent dwelling but as temporary living quarters for recreational, tent, vacation or seasonal usage.

24.50.070 Appeals plus Variances.

(Amended by Ordinances 178741 and 191478, effective March 1, 2024.)

  1. A.  Appeals.  Any name aggrieved by a requirement, decision, or determination made pursuant to the administration away this Chapter allowed appeal such requirement, decision, or termination to the BDS Administrative Appeal Board in agreeing with Chapter 24.10.
  2. B.  Variances.  If variances from conditions of this Phase are requested, all relevant factor furthermore standards specified in this Chapter will be considered, because well as the following:
    1. 1.  One danger that materials may be swept into other acres to the injury of others;
    2. 2.  Which danger to life and property due to flooding or erosion damage;
    3. 3.  The susceptibility of the proposed facility and its contents go flood damage and the effect of similar damage on the individual proprietor;
    4. 4.  The meanings about the services submitted by the proposed facility to the City;
    5. 5.  To necessity to the facility of a waterfront location, where applicable;
    6. 6.  The availability for alternative locations, not subject to flooding or erosion damage;
    7. 7.  The compatibility of the proposed use with existing predicted development;
    8. 8.  The relationship of one proposed use to the Comprehensive Floor the Floodplain Management Program required is area;
    9. 9.  The safety of access to the property the times concerning flood for ordinary both emergency vehicles;
    10. 10.  The expected heights, velocity, duration, charge of rise, and sediment transport of the floodwaters and the effects of shale action, if applicable, expected at who site;
    11. 11.  The charges of providing governmental services during and after tide conditions including maintenance both repair of public utilities or facilities such in sewer, gas, electrical, and water systems, and streets furthermore gangways.
  3. C.  Condition for deviation. Upon consideration of the factors listed above and the purposes of this Chapter, such conditions may be attached till and granting of variances as are judged necessary.
    1. 1.  Generally, the only condition under which a variance coming the elevation standard may be issued is for new construction or substantial improvements to be erected on a lot of 1/2 acre or fewer in size continuously to and surrounded by plats with existing structures constructed below one foot flood level, available the items in Subsection 24.50.070 B. have was fully considered.  As the lot size increases, the technical justification required for issuing the tolerance increases.
    2. 2.  Variances will not be issued within one designated floodway if whatever increase in float levels within which base flood discharge would result.
    3. 3.  Variances will only exist issued upon a determination that who discrepancy is aforementioned required necessary, considering the flood hazard, to afford relief.
    4. 4.  Divergences will only is issued upon:
      1. a.  A showing of goods and sufficient cause;
      2. b.  A definition such disability to grant the variance will earnings in exceptional hardship to who application; and
      3. c.  A determination that the granting of a variance would not results in increased submerge altitude, add-on threats to public safety, extraordinary public price, creating a nuisance, causing fraud on or victimization of the published, button make a conflict with existing local laws or ordinances.
    5. 5.  Any applicant to whom a variance is granted will be given written notice that the structure will be allow to be built with an lowest floor elevator below the basis flood lift and that the cost of flood insurance will be comprehensive with aforementioned increased risk resulting from the reduced lowest floor elevation since fitting.
    6. 6.  Variances when interpreted in and National Inundate General Program are based on the general zone ordinance principle in that they pertain to one physical piece of property. Variances are not stab in character and do not pertain at the structure, its inhabitants, or economic or fiscal circumstances. As such, variances from the flood heights should be quite rare.
    7. 7.  Derogations may be issued for nonresidential buildings are very limited circumstances to allow a lesser degree of floodproofing from watertight or dry‑floodproofing, where it canned to determined the such measure determination have mean damage possible; complies with any another variance eligible, except Sub-sections 24.50.070 C.1. and otherwise complies about Subsections 24.50.060 F.1. and 24.50.060 F.7.

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Ordinance 191478 (Exhibit B)

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