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Ketchikan BannerALASKA RISK MAP PROGRAM

Ketchikan Gateway Borough Risk MAP Study


FEMA and the State of Alaska are conducted 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 included (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 completed for 0.08 miles of Carlanna Creek.
  • Hydrological study includes:
    • USGS Regional Regression equations used to develop peak flow discharges for riverine flooding sources.
    • Ketchikan Creek 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.
  • All of the above datasets are 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

The Letter of Final Base Flood Elevation Determinations (LFD) was issued on October 11, 2023. An LFD is a letter FEMA sends to the Chief Executive Officer of a community initiating the six-month compliance period, stating that a new or updated FIRM and FIS will become effective in six months.

In early February 2024, the draft Revalidation Letter was submitted for review. The Revalidation Letter identifies effective Letters of Map Change (LOMC) [i.e., Letters of Map Amendment (LOMAs) and Letters of Map Revision-based on Fill (LOMR-Fs)] for properties and/or structures located in the community that will still be valid after the new maps become effective. The Revalidation Letter was approved in mid-February 2024 and issued on April 4, 2024.

The Ketchikan Gateway Borough recently updated the Borough floodplain management regulations to be compliant with the National Flood Insurance Program (NFIP) and associated state regulations, which were adopted on March 5, 2024.

The Borough's FIRMs and FIS became effective on April 11, 2024, six months following the issuance of the LFD. Effective maps are available for download on FEMA’s Flood Map Service Center website (https://msc.fema.gov/portal/advanceSearch). Community officials were sent the Revalidation Letter that lists previously issued LOMCs that have been reaffirmed for the new FIRM. The Revalidation Letter became effective one day after the publication of the community’s new final FIRM. The Revalidation Letter does not list LOMCs that have been incorporated into the revised panel, LOMCs that are superseded by new or revised mapping, or LOMCs that are no longer valid. While the Summary of Map Actions (SOMA) is a preliminary assessment of which LOMCs may still be valid after the new maps are issued, the Revalidation Letter is the final, effective determination of the LOMCs which remain valid. The SOMA and the Revalidation Letter are meant to assist community officials in the maintenance of the community’s FIRM.

FEMA has prepared two viewers to aid in the communities’ review of the revised maps as linked below:

  • Preliminary (2017) vs. Revised Preliminary (2020): https://fema.maps.arcgis.com/home/item.html?id=c9870d6167cc4b1d8d305d2f5b5e1e46
  • Effective (1990) vs. Revised Preliminary (2020): https://fema.maps.arcgis.com/home/item.html?id=566088f4e3aa4429a345a7e01cc2715a
  • 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 August 28, 2020
    2nd Consultation Coordinators (CCO) Meeting (Webinar) December 8, 2020
    StoryMap Release May 3, 2021
    2nd Public Meeting/Workshop November 2, 2024
    2nd 90-Day Appeal Period Begins November 16, 2022
    2nd 90-Day Appeal Period Ends February 14, 2023
    Letter of Final Determination October 11, 2023
    Revalidation Letter Distribution April 4, 2024
    Maps and FIS become Effective April 11, 2024
    Revalidation Letter goes into Effect April 12, 2024

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

    Map of Ketchikan Study Scope

    Click on image to open larger map

    The red line indicates denotes the extent of the Ketchikan Gateway Borough coastal mapping study
    Ketchikan Study Scope Map

    Ketchikan Discovery
    (FEMA Region X Workspace)
    Ketchikan Gateway Borough
    PIN Website
    FEMA Region X
    Risk MAP Newsletters

    For more information contact:

    Rebecca Rein

    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) 269-3037
    Fax (907)269-4539
    Email: rebecca.rein@alaska.gov