CITY OF PORTLAND, OREGON MULTNOMAH, CLACKAMAS, AND WASHINGTON COUNTIES

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1 CITY OF PORTLAND, OREGON MULTNOMAH, CLACKAMAS, AND WASHINGTON COUNTIES REVISED: NOVEMBER 26, 2010 Federal Emergency Management Agency Flood Insurance Study Number V000B

2 NOTICE TO FLOOD INSURANCE STUDY USERS Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study may not contain all data available within the repository. It is advisable to contact the community repository located at 1221 SW 4 th Avenue, Room 230, Portland, OR 97204, for any additional data. As part of these studies, the format of the map panels changed. Previously, flood hazard information was shown on both the Flood Insurance Rate Map and Flood Boundary and Floodway Map. In the new format, all Base Flood Elevations, cross sections, zone designations, and floodplain and floodway boundary delineations are shown on the Flood Insurance Rate Map, and the Flood Boundary and Floodway Map has been eliminated. Some flood insurance zone designations were changed to reflect the new format. Areas previously shown as Zones A1-A30 were changed to Zone X (unshaded). In addition, all zone designations and reach determinations were removed from the profile panels in the Flood Insurance Study report. Part of all of this FIS may be revised and republished at any time. In addition, part of this FIS may be revised by a Letter of Map Revision process, which does not involve republication or redistribution of the FIS. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current FIS report components. This FIS report was revised on November 26, Users should refer to Section 10.0, Revisions Descriptions, for further information. Section 10.0 is intended to present the most up-to-date information for specific portions of this FIS report. Therefore, users of this FIS report should be aware that the information presented in Section 10.0 supercedes information in Sections 1.0 through 9.0 of this FIS report.

3 10.0 REVISIONS DESCRIPTIONS First Revision...35

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15 Flooding Source and Location Table 2. Summary of Elevations 10-Percent-Annual- Chance Elevation (Feet NAVD) 2-Percent-Annual- Chance 1-Percent-Annual- Chance 0.2-Percent-Annual- Chance Columbia River At Vancouver, Washington (RM 106.5) Force Lake In vicinity of North Victory Boulevard & North Force Avenue Internal Drainage - NE 33rd Basin North of NE Elrod Road approximately between NE 33rd Drive and NE Airport Perimeter Drive Approximately 150 feet east of Peninsula Drainage Canal Approximately 550 feet North of NE Elrod Drive 350 feet West of NE 33rd Drive Approximately 270 feet South East of the intersection between NE Elrod Road and NE 33rd Drive South of NE Elrod Road approximately between NE 33rd Drive and NE Airport Perimeter Drive Peninsula Drainage District No. 1 In vicinity of North Force Avenue & North Broadacre Street Willamette River At Morrison Bridge (RM 12.8) Data Not Available 11

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24 FLOODING SOURCE CROSS SECTION DISTANCE 1 COLUMBIA RIVER A B C D E F G H I J K FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION SECTION MEAN WITHOUT WITH WIDTH 4 REGULATORY 2 AREA VELOCITY FLOODWAY 3 FLOODWAY 3 INCREASE (FEET) (SQ.FEET) (FEET/SEC.) (FEET NAVD) (FEET NAVD) (FEET NAVD) (FEET) ,233 / , ,630 / , ,423 / 2, , ,285 / 2, , ,594 / 3, , ,360 / 3, , ,000 / 3, , ,619 / 1, , ,245 / 1, , ,292 / 1, , ,773 / , Miles Above Mouth 2 Elevations based on combined stage-frequency curve 3 Elevations based on HEC-2 Model calibrated to approximate 100-year combined-stage frequency curve 4 Width/width within City of Portland 5 Width does not include island TABLE 4 FEDERAL EMERGENCY MANAGEMENT AGENCY CITY OF PORTLAND, OR (MULTNOMAH, CLACKAMAS, AND WASHINGTON COS.) FLOODWAY DATA COLUMBIA RIVER

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28 FLOODING SOURCE CROSS SECTION DISTANCE 1 JOHNSON CREEK A B C D E F G H I J K L M N O P Q R S T U V W X Y Z FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION SECTION MEAN WITHOUT WITH WIDTH REGULATORY INCREASE AREA VELOCITY FLOODWAY FLOODWAY (FEET) (SQ.FEET) (FEET/SEC.) (FEET NAVD) (FEET NAVD) (FEET NAVD) (FEET) , , , , , Miles Above Mouth TABLE 4 FEDERAL EMERGENCY MANAGEMENT AGENCY CITY OF PORTLAND, OR (MULTNOMAH, CLACKAMAS, AND WASHINGTON COS.) FLOODWAY DATA JOHNSON CREEK

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30 FLOODING SOURCE CROSS SECTION DISTANCE 1 JOHNSON CREEK (cont.) BA BB BC BD BE BF WIDTH 2 FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION SECTION MEAN WITHOUT WITH REGULATORY AREA VELOCITY FLOODWAY FLOODWAY INCREASE (FEET) (SQ.FEET) (FEET/SEC.) (FEET NAVD) (FEET NAVD) (FEET NAVD) (FEET) / / / / / / Miles Above Mouth 2 Width/width within City of Portland 3 Entire width outside City of Portland TABLE 4 FEDERAL EMERGENCY MANAGEMENT AGENCY CITY OF PORTLAND, OR (MULTNOMAH, CLACKAMAS, AND WASHINGTON COS.) FLOODWAY DATA JOHNSON CREEK

31 FLOODING SOURCE CROSS SECTION DISTANCE 1 WILLAMETTE RIVER A B C D E F G H I J K L M N O P Q R S T U V W X Y Z WIDTH FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION SECTION MEAN WITHOUT WITH REGULATORY AREA VELOCITY FLOODWAY 2 FLOODWAY 2 INCREASE (FEET) (SQ.FEET) (FEET/SEC.) (FEET NAVD) (FEET NAVD) (FEET NAVD) (FEET) ,600 / , ,700 / , ,073 / 1, , , , , , , , ,420 85, ,417 80, ,440 82, , , , , ,697 98, ,023 68, , , ,144 70, , ,197 67, ,295 69, ,378 66, ,339 69, ,339 69, ,371 73, ,585 73, , , , , Miles Above Mouth 2 Elevations computed without consideration of influence from Columbia River 3 Width does not include island 4 Width/width within City of Portland TABLE 4 FEDERAL EMERGENCY MANAGEMENT AGENCY CITY OF PORTLAND, OR (MULTNOMAH, CLACKAMAS, AND WASHINGTON COS.) FLOODWAY DATA WILLAMETTE RIVER

32 FLOODING SOURCE CROSS SECTION DISTANCE 1 WILLAMETTE RIVER (cont'd) AA AB AC AD WIDTH FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION SECTION MEAN WITHOUT WITH REGULATORY AREA VELOCITY FLOODWAY 2 FLOODWAY 2 INCREASE (FEET) (SQ.FEET) (FEET/SEC.) (FEET NAVD) (FEET NAVD) (FEET NAVD) (FEET) ,385 59, ,405 69, ,165 54, ,415 74, Miles Above Mouth 2 Elevations computed without consideration of influence from Columbia River TABLE 4 FEDERAL EMERGENCY MANAGEMENT AGENCY CITY OF PORTLAND, OR (MULTNOMAH, CLACKAMAS, AND WASHINGTON COS.) FLOODWAY DATA WILLAMETTE RIVER

33 The area between the floodway and 100-year floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the WSEL of the 100-year flood more than 1 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 1. Figure 1. Floodway Schematic 5.0 INSURANCE APPLICATION For flood insurance rating purposes, flood insurance zone designations are assigned to a community based on the results of the engineering analyses. These zones are as follows: Zone A Zone A is the flood insurance rate zone that corresponds to the 100-year floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no BFEs or depths are shown within this zone. Zone AE Zone AE is the flood insurance rate zone that corresponds to the 100-year floodplains that are determined in the FIS by detailed methods. Whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Zone AH Zone AH is the flood insurance rate zone that corresponds to the areas of 100-year shallow flooding (usually areas of ponding) where average depths are between 1 and 3 feet. Whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. 29

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38 U.S. Department of the Army, Corps of Engineers, Portland District, Johnson Creek, Flooded Area Update, December U.S. Department of the Army, Corps of Engineers, Portland District, Crystal Springs Creek, Flooded Area Update, March U.S. Department of the Army, Corps of Engineers, Hydrologic Engineering Center, HEC-HMS Hydrologic Modeling System, Version 1.0, Davis, California, March Federal Emergency Management Agency, Guidelines and Specifications for Flood Hazard Mapping Partners, February U.S. Department of the Army, Corps of Engineers, Portland District, Peninsula Drainage District No. 1, Detailed Product Report, Section 205, September Philip Williams and Associates, Ltd., for City of Portland, FEMA Physical Map Revision Application for Johnson Creek, superseded LOMR Case No P, January, 1, City of Milwaukie, Federal Emergency Management Agency MT-2 Form 1, Appeals to Johnson Creek LOMR Case No P, May 3, Puget Sound LiDAR Consortium/Puget Sound Regional Council, Bare Earth LiDAR ASCII Points, Scale 1:12,000, Contour Interval 2 feet, Aerial Survey of March 13,

39 10.0 REVISIONS DESCRIPTIONS This section has been added to provide information regarding significant revisions made since the original FIS report was printed. Future revisions may be made that do not result in the republishing of the FIS report. To assure that users are aware of all revisions, it is advisable to contact the community repository of flood hazard data located at the City of Portland, Bureau of Environmental Services, 1221 SW 4 th Avenue, Room 230, Portland, OR, First Revision [November 26, 2010] For this revision, the floodplain boundaries within the City of Portland for the Columbia River, Columbia Slough, and a portion of the Willamette River were revised based on 2 foot contour interval topographic data developed from LiDAR data created by the Puget Sound LiDAR Consortium (Reference 49). The data can be used at a horizontal scale of 1:12,000 (1 inch = 1,000 feet) or smaller. WEST Consultants, Inc. performed this work for the Federal Emergency Management Agency (FEMA), under Contract No. EMS-2001-CO-0068 and completed it in August The FIRM panels being revised are 0020, 0040, 0060, 0080, 0085, 0105, 0110, 0120, and The results of this revision were reviewed at the final CCO Meeting held on April 7, All problems raised at that meeting have been addressed in this revision. This revision also incorporates three Letters of Map Revision (LOMR). LOMR case number P, dated July 20, 2005, revised BFEs for the Peninsula Drainage District No. 1 as shown on panels 0080 and Table 2 Summary of Elevations has been updated to reflect this data. LOMR case number P, dated January 28, 2008, revised SFHA boundaries and BFEs for the area east of the Peninsula Drainage Canal and west of NE Airport Perimeter Road as shown on panels 0085 and Table 2 Summary of Elevations has been updated to reflect this data. LOMR case number P, dated January 21, 2009, revised SFHA boundaries and BFEs along Johnson Creek in the vicinity of cross sections L through Q. This revision covers part of panels 0184 and 0203, which are not being revised at this time, however, the FDT, Profiles, and DFIRM DB do include this updated data. Other than the above LOMRs, no new engineering analyses were incorporated as part of this revision. 35

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51 SOUTHEAST 82ND AVENUE

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61 CITY OF PORTLAND MULTNOMAH COUNTY MULTNOMAH COUNTY CITY OF PORTLAND

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