Alaska Risk MAP Program

Community Risk MAP Studies: Fairbanks North Star Borough

Approximate Flood Study

Project History

FEMA Region 10, Fairbanks North Star Borough (FNSB), and the State of Alaska identified the FNSB Approximate flood study as a priority for FEMA's Risk MAP program. The State determines its priorities based on population at risk to hazards, recent events, and community interest. FEMA, State, and local stakeholders participated in a Risk MAP Kick-Off meeting held August 27, 2020. The community did not have any concerns or additional needs during that meeting.

This project commenced in September 2020. FEMA's mapping contractor obtained 2017/2018 Light Detection and Ranging Digital Terrain Model (LiDAR/DTM) datasets from the Alaska Division of Geological and Geophysical Surveys (DGGS) Elevation portal. Hydrology using Regression/Gage along with Rainfall Runoff was finalized in March 2021. Hydraulics for Phase 1 of the Base Level Engineering (BLE) project was completed in mid-July 2021. FNSB requested approximately 215 miles of additional BLE stream reaches in January 2021. This added footprint was considered during the next phase of the project, which started in August 2021. Hydrology for the additional streams and multi-frequency results for all streams were completed in December 2021. Field Survey was also completed in December 2021. The Zone A Hydraulic study was completed in October 2022. The Tanana River Study Hydrology was submitted to FEMA and finalized in December 2021. In a separate project, the Hydraulic study for the Tanana River was submitted by the consulting firm,HDR in October 2022.

Hydraulic modeling for the Approximate (Zone A) Studies was completed in October 2022. FEMA's mapping contractor has incorporated the mapping outputs into the Draft DFIRM database, which will be used for Preliminary Production. The Draft Zone A floodplain mapping and associated outputs have been placed on the FEMA GeoPlatform (see link below).

Part of the Floodplain Mapping process is adding effective floodplain within the projected panels. The effective floodplains were digitized from the previous non-modernized community panels. The effective floodplains will be tied into new flood study data. This new panel footprint is included with the GeoPlatform.

Tie-ins between the Tanana River flood study, effective flood studies, and the Zone A study have been completed. The Flood Risk Review (FRR) meeting was held on July 6, 2023. After the FRR, it was determined a follow-up meeting was necessary to allow the new FNSB Floodplain Administrator to have direct involvement. This follow-up meeting was held on August 29, 2023. During the follow-up meeting, a comment on the Perkins Landing area Tanana River Floodway delineation was discussed. FNSB requested another look at that area to be more in line with the river’s edge. The consulting firm, HDR, was tasked with reviewing the model and coordinating with FNSB. An extended comment period was provided to FNSB and set for October 1, 2023.

On September 29, 2023, FNSB provided comments on the FY19 & FY21 studies via email. HDR submitted Tanana River Floodway revisions to FEMA's mapping contractor on October 3, 2023. On November 6, 2023, FEMA and FEMA's mapping contractor held a call with FNSB to go over the comments. The only remaining comment not addressed during that call regarded the flood mapping for Isabella Creek in the Bentley Avenue area. FEMA Region 10 and FEMA's mapping contractor revisited the modeling approach for Isabella Creek.

The revised floodplains for Tanana River and Isabella Creek have been added to the Risk MAP Project Portfolio at the FEMA GeoPlatform link below [see “Draft (2023.12)” tab].

The Draft results were presented to FNSB via email on December 14, 2023. No further comments were received. The FRR Comment Resolution was completed in January 2024.

Data from these efforts can be viewed at the following locations:

• FEMA GeoPlatform and Flood Study Data:
• Zone A Study Draft Map Viewer:Fairbanks North Star Borough, Alaska - Draft (2022.10.04) - Viewer
• Flood Study Viewer (Zone A/Tanana):Fairbanks North Star Borough - Flood Study Viewer (2023.01)
• FNSB Risk MAP Project Portfolio (all projects):Fairbanks North Star Borough, Alaska - Risk MAP Project Portfolio
• Flood Study Data Workmaps (Expiration Date: 2/18/2023):Fairbanks North Star Borough, Alaska - Risk MAP Project Portfolio
• Project Deliverables (Risk MAP Contacts, Project Area Scope Map, Draft Maps)**: https://www.starr-team.com/starr/RegionalWorkspaces/RegionX/FNSB_AK_DFIRM-PTS_Support_to_CTP/SitePages/Home.aspx

Recent Activity

Following the Flood Risk Review (FRR) comment resolutions, a coordination call between FEMA, FNSB, FEMA's mapping contractor, State of Alaska, and FEMA’s community engagement contractor, Resilience Action Partners, was held on January 10, 2024, to discuss the upcoming Public Outreach activities. Resilience Action Partners presented community outreach opportunities and resources with FNSB. A proposed timeline for next steps was also provided.

As part of the outreach activities, the Flood Risk Products (FRPs) were discussed, which include Changes Since Last FIRM (Flood Insurance Rate Map), Flood Depth Grids, and Water Surface Elevation Grids. These supplemental products include additional information on the Zone A Approximate studies and the Tanana River. The plan is to finalize these products in the coming month and provide to FNSB.

Prior to community outreach, the project team will add 0.2% annual chance flood hazard areas to studied Zone A reaches and host on the FEMA GeoPlatform. These hazard areas will provide additional hazard information to make risk-informed decisions.

Next Steps

FEMA's mapping contractor will be finalizing the DFIRM Database and starting the Preliminary Mapping Process, with a Preliminary Release tentatively scheduled for September 2024.

Along with the Preliminary production, FEMA and Resilience Action Partners will be coordinating with FNSB on any Preliminary Outreach activities.

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

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

Chena Slough Flood Study

The Fairbanks North Star Borough (FNSB) identified an updated flood study for Chena Slough as a local mapping need while an effective Flood Insurance Study, dated March 17, 2014, was being finalized. FEMA was unable to include an updated flood study for Chena Slough at that time. Since then, FNSB completed an updated flood study for Chena Slough through FEMA's Cooperating Technical Partners (CTP) program. FEMA’s mapping contractor was tasked with performing Quality Assurance/Quality Control(QA/QC) of the flood study, and to incorporate the updated study data into Preliminary Flood Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) for public release and review.

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

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

Revised 08/23/2024