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Alaska Risk MAP Program

Community Risk MAP Studies: Matanuska-Susitna Borough

FEMA and the State of Alaska are conducting a Risk MAP Study in the Matanuska-Susitna Borough that began in 2013.

Risk MAP Discovery Documents Risk MAP Study Scope Documents Draft Workmaps - Released August 28, 2015 Flood Risk Review Meeting Preliminary Flood Insurance Rate Maps (FIRMs) - Released August 19, 2016 Preliminary Flood Insurance Study and FIRM Database - Released August 16, 2016 Consultation Coordination Officer (CCO) Meeting Resilience Documents and Workshop Region X Service Center Quarterly Reports

Study Scope

The scope of work of the Matanuska-Susitna Borough Risk MAP Study includes (see also the map below):

Detailed hydrology and hydraulic modeling to include 71.9 miles of riverine study, perform approximate riverine analysis for 316.6 miles, and delineate 15.4 miles of existing areas. Floodplain boundaries will be updated for the 1-percent and 0.2-percent-annual-chance (100- and 500-year) flood events. The rivers to be updated include:

  • Updated detailed modeling (Zone AE) will be completed for:
    • Little Susitna River (including Split Flows 1-3) = 39.2 mile
    • Willow Creek = 13.3 miles
    • Willow Creek Tributary = 7.1 miles
  • Limited detail modeling (Zone A with structures) will be completed for:
    • Wasilla Creek = 10.7 miles
  • Updated Approximate Studies (Zone A) will be completed for:
    • Upper Matanuska River = 14 miles
    • Point MacKenzie = 2 miles – roughly from Walsop Road to 2 miles downstream of Walsop Road
    • Various Zone A = 289.9 miles
  • Redelineation of Effective Detailed Studies (Zone AE) will be completed for:
    • Deception Creek and Tributaries 1-3 = 15.4 miles

US Army Corps of Engineers (USACE) Studies (Leverage - Zone AE) will also be incorporated to include:

  • Matanuska River = 3.9 miles
  • Knik River = 2.7 miles
  • Bodenburg Creek = 5.7 miles

Regulatory Products

  • Preparation of a regulatory Flood Insurance Study (FIS) Report document to the Community. 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.
  • Preparation of a regulatory Flood Insurance Rate Map (FIRM) map 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 September 2015.
  • Collect LiDAR in Summer 2015. This data will be delivered to the community by Fall 2015.
  • All of the above datasets will be in the in the North American Vertical Datum of 1988.
  • The State and FEMA will provide guidance, feedback, coordination and technical support throughout the Risk MAP Project Life Cycle.

Non-Regulatory Products and Technical Assistance

  • A Changes Since Last FIRM map and dataset will be prepared 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.
  • 10%, 4%, 2%, 1%, and 0.2% annual-chance depth grids will be developed for detailed analysis and 1% annual chance depth grids for 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.
  • A non-regulatory Risk Report will be prepared 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, landslide, and wildfire 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.
  • A Flood Risk Database will be developed which houses data collected, 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.
  • Areas will be highlighted where risk reduction actions may produce the highest return on investment.
  • The Borough will be provided with technical assistance for HAZUS projects.
  • The Borough will be provided with Areas of Mitigation Interest findings and recommendations based on best available data.
  • The State and FEMA will provide guidance, feedback, coordination and technical support throughout the Risk MAP Project Life Cycle.

Project Status

Recent Activity

The Final Flood Hazard Determinations have posted in the Federal Register as of May 20, 2019. The Letter of Final BFE Determinations (LFD) was issued on March 27, 2019. An LFD is a letter FEMA sends to the Chief Executive Officer of a community stating that a new or updated Flood Insurance Rate Map (FIRM) or Digital FIRM will become effective in six months (September 27, 2019). The letter also notifies each affected flood-prone community participating in the National Flood Insurance Program (NFIP) that it must adopt a compliant floodplain management ordinance by the maps’ effective date to remain participants in good standing. Not doing so will lead to suspension from the NFIP. If assistance is needed, communities should contact their State NFIP Coordinator, Jimmy Smith, at jimmy.smith@alaska.gov, or the Regional FEMA NFIP specialist, Karen Wood-McGuiness at Karen.Wood- McGuiness@fema.dhs.gov.

A swipe map comparing effective and preliminary flood hazard areas for the Matanuska-Susitna Borough is now available.

Purpose: The map compares effective floodplains from 2011 (left panel) with preliminary floodplains from 2016 (right panel) where DFIRM data is available.

A multi-hazard Risk Report and a Resilience Dashboard for the Matanuska-Susitna Borough have been prepared as part of the ongoing Risk MAP study. The Risk Report includes a risk assessment of earthquake, flood, and landslide hazards. Hazus, FEMA’s loss estimation software, was used to assess the potential building losses from earthquake and flood hazards.

The draft multi-hazard Risk Report and Resilience Dashboard were provided to Matanuska-Susitna Borough for comment on January 10, 2017. The draft Risk Report and Resilience Dashboard can be found at the following hyperlinks:

Comments on the draft Risk Report and Resilience Dashboard should be sent to Sally Russell Cox, the State Risk MAP Coordinator.

Next Steps

The FIRMs and Flood Insurance Study (FIS) will become effective on September 27, 2019, six months after the LFD. Effective maps will be available for download on FEMA’s Flood Map Service Center website. Around this date, your community officials will receive in the mail the Revalidation Letter that lists previously issued Letters of Map Change (LOMC) that have been reaffirmed for the new FIRM. The Revalidation Letter becomes effective one day after the publication of a community’s new or revised 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.

Once all review comments on the draft Risk Report and Resilience Dashboard have been addressed, a Resilience Workshop will be held to discuss the results of the risk assessments and risk reduction strategies.

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

Activity Actual or Projected End Date
Discovery Interview March 11, 2013
Discovery Meeting April 23, 2013
Flood Study Kick-Off Meeting December 13, 2013
Draft Work Maps Issued August 28, 2015
Flood Risk Review Meeting January 20, 2016
Preliminary DFIRM/FIS Release August 19, 2016
Consultation Coordination Officers (CCO) Meeting January 4, 2017
Draft Multi-Hazard Risk Report January 10, 2017
Public Meeting/Workshop March 15-16, 2017
90-Day Appeal Period Starts October 27, 2017
90-Day Appeal Period Ends January 25, 2018
Revised Preliminary DFIRM/FIS Release August 24, 2018
Letter of Final Determination March 27, 2019
Risk MAP Resilience Workshop To Be Determined*
Delivery of Final Risk Report and Risk Assessment Database To Be Determined*
Maps and FIS become Effective September 27, 2019*

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

Map of Matanuska-Susitna Borough Study Scope

Matanuska-Susitna 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 1640, Anchorage, AK 99501-3569
Phone (907) 269-4588 Fax (907)269-4539
Email: sally.cox@alaska.gov