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Alaska Risk Map Program

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Ketchikan Gateway Borough Risk MAP Study

FEMA and the State of Alaska are conducting a coastal Risk MAP Study in the Ketchikan Gateway Borough that began in 2013.

Ketchikan Gateway Borough Risk MAP Discovery Documents Risk MAP Study Scope Documents Draft Workmaps Flood Risk Review Meeting Documents Preliminary Flood Insurance Study and Flood Insurance Rate Map (FIRM) Database Preliminary Flood Insurance Rate Maps Resilience Documents and Workshop Region X Service Center Quarterly Reports

Study Scope

The scope of work of the Ketchikan Gateway Borough Risk MAP Study includes (see also the map below):

  • A detailed coastal flood hazard analysis (34 miles with 12 proposed transects of Tongass Narrows/Gulf of Alaska) including the collection of storm surge (coastal hydrology) and overland wave height analysis (coastal hydraulics), as well as floodplain boundaries for 1-percent and 0.2-percent-annual-chance (100- and 500-year) flood events.
  • Updated detailed modeling will be completed for 0.99 miles on Hoadley Creek, 1.2 miles of Ketchikan Creek, and 1 mile on Schoenbar Creek.
  • Redelineation using new LiDAR will be completed for 0.08 miles of Carlanna Creek.
  • Hydrological study includes:
    • USGS Regional Regression equations are used to develop peak flow discharges for riverine flooding sources.
    • Ketchikan Creek will be done using Gage or Mid-Range Analysis
  • Hydraulic study includes one-dimensional steady-state hydraulic models with best available topographic data, field surveyed cross sections and structures.

Regulatory Products

  • A Flood Insurance Study (FIS) Report. A FIS is a book that contains information regarding flooding in a community and is developed in conjunction with the FIRM. The FIS, also known as a flood elevation study, frequently contains a narrative of the flood history of a community and discusses the engineering methods used to develop the FIRM. The study also contains flood profiles for studied flooding sources and can be used to determine Base Flood Elevations for some areas.
  • Flood Insurance Rate Map (FIRM) for all panels within the Community which identifies the Community's flood zones, base flood elevations, and floodplain boundaries. This map is used to determine where the purchase of flood insurance is required for properties with federally-backed mortgages. The preliminary FIS and DFIRM’s are scheduled to be released in Winter/Spring 2016.
  • All of the above datasets will be in the in the North American Vertical Datum of 1988.

Non-Regulatory Products

  • A Changes Since Last FIRM Map and Dataset that identifies areas where the Special Flood Hazard Area, floodway, and/or flood zone designations have changed since the previous flood study. Engineering factors that may have contributed to the changes such as data used and level of study performed will also be identified.
    • Estimates of structures affected by the changes will be quantified and summarized to capture increases/decreases in known risk areas and enable local officials to better plan for outreach needs.
  • 1% Annual-Chance Depth Grids for coastal areas and approximate riverine analysis. Depth grids depict the depth of flooding at locations throughout a community and when combined with other information, such as first floor elevations, are invaluable in understanding risk.
  • Areas of Inundation associated with +l, 2, and 3 feet increase to the base flood elevation for coasta l areas to be used for planning purposes to represent sea level rise. Elevation increase values can also be adjusted using local sea level rise data as requested by the community.
  • Risk Report which include narratives on multiple hazards and risk exposure, and explains the risk assessment methodology and results for each community. The risk report will provide loss estimations using Hazus for flood, earthquake, and tsunami hazards. Flood depth grids and USGS ShakeMaps will be incorporated into the Hazus analysis. Local data will be added to Hazus for more accurate results. Other natural hazards will include a summary and an exposure analysis.
  • Flood Risk Database which houses data collect ed, created, and analyzed during the project. This data can be used by the Community to recreate maps, develop reports and other products, and to perform additional analysis. Highlight areas where risk reduction actions may produce the highest return on investment. Technical assistance for HAZUS projects.
  • Areas of Mitigation Interest findings and recommendations based on best available data.

Project Status

Project History

A webinar meeting was held on February 15, 2019 to share the draft floodplain updates and discuss the areas that have changed due to the comments received during the first appeal period. Ketchikan Gateway Borough had submitted a package of comments regarding the validity of the Preliminary FIRM.

The comments submitted concern the study methods, the topographic data used in the study, the delineation of the Special Flood Hazard Areas (SFHAs), and the BFEs. The project team has reviewed and updated the coastal flood analysis and floodplain delineation along the coast in response to the feedback submitted. The updates included additional coastal transects in the mapping, changes in the roughness coefficients, plateau overtopping calculations at additional locations, and revisions to the floodplain delineation to more precisely follow the computed 1-percent flood elevation. As a follow up to the webinar, the project team is preparing information to show how wave runup can impact properties.

FEMA held a comment resolution meeting with the Ketchikan Gateway Borough on July 24, 2019 to discuss the community comments and proposed changes in more detail. Following the comment resolution meeting, the coastal engineering team and a team of field surveyors visited locations of concern identified by Borough officials to verify the topography. The information collected during this field visit was used to make further updates to the draft SFHA along the coast. Following these updates, FEMA's mapping contractor prepared a resolution letter outlining the changes made in response to the community comments.

Recent Activity

FEMA's mapping contractor is in the process of creating revised preliminary products based on the input received. The revised preliminary products will include the updated coastal analysis and mapping and revised hydraulic analysis with reduced peak flow estimates based on updated guidance provided in the Scientific Investigation Report (SIR) 2016-5024 titled “Estimating Flood Magnitude and Frequency at Gaged and Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada, Based on Data through Water Year 2012” (Curran, Barth, Veilleux, & Ourso, 2016).

Next Steps

FEMA"s mapping contractor will prepare a resolution letter outlining the changes made in response to the community comments. Revised preliminary panels will be released and a second appeal period will be initiated. The revised preliminary products are expected to be released in July 2020. The timing of the appeal period will be determined in the future.

A multi-hazard Risk Report for the Ketchikan area is being developed as part of the ongoing Risk MAP study. The Risk Report will include a risk assessment of earthquake, flooding, landslide, tsunami, and dam failure hazards. HAZUS, FEMA’s loss estimation software, will be used to assess earthquake and flood hazards.

Once all risk assessments are completed, they will be compiled into the Risk MAP Risk Report and a Resilience Workshop will be held to discuss the results and risk reduction strategies.

Project Schedule

The following table illustrates project status and includes major milestones with dates:

Activity Actual or Projected End Date
Discovery Interview June 17, 2013
Discovery Meeting August 7, 2013
Base Map Acquisition February 2, 2014
Discovery Report Summer 2014
Perform Field Survey August 31, 2014
Develop Topographic Data November 30, 2014
Hydrologic Analysis December 31, 2014
Perform Coastal Analysis July 17, 2015
Hydraulic Analysis July 17, 2015
Perform Floodplain Mapping September 2015
Develop DFIRM Database September 25, 2015
Draft Work Maps March 7, 2016
Flood Risk Review Meeting August 4, 2016
Preliminary DFIRM/FIS Release May 5, 2017
Consultation Coordination Officers (CCO) Meeting July 18, 2017
Public Meeting/Workshop January 25, 2018
1st 90-Day Appeal Period Begins February 2, 2018
1st 90-Day Appeal Period Ends May 2, 2018
Draft Multi-Hazard Risk Report November 2018
Comment Resolution Meeting July 24, 2019
Revised Preliminary FIRM/FIS Release July 2020*
2nd 90-Day Appeal Period Begins To Be Determined
2nd 90-Day Appeal Period Ends To Be Determined
Letter of Final Determination To Be Determined
Delivery of Final Risk Report and Risk Assessment Database To Be Determined
Maps and FIS become Effective To Be Determined

*All projected dates are subject to revision as the project progresses.

Map of Ketchikan Study Scope

The red line indicates denotes the extent of the Ketchikan Gateway Borough coastal mapping study
Ketchikan Study Scope Map
Click on image to open larger map

Contact for More Information

Sally Russell Cox
State of Alaska Risk MAP Coordinator
Division of Community and Regional Affairs
Department of Commerce, Community, and Economic Development
550 West 7th Avenue, Suite 1650
Anchorage, AK 99501-3569
Phone (907) 269-4588
Fax (907)269-4539