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In September 2022, the west coast of Alaska was struck by Extratropical Typhoon Merbok, generating significant storm surge that caused severe flooding, erosion damage, and loss of subsistence infrastructure to over 35 communities along more than 1300 miles of Alaska’s western coast.

USGS participated in a multi-agency response to the storm and is supporting disaster relief efforts in three key ways:

1. Developing flood hazard maps of the storm event 

USGS Geologists Ann Gibbs and Alex Nereson collaborated with Richard Buzard (University of Alaska, Fairbanks) and the Alaska Division of Geological and Geophysical Surveys (DGGS) to develop rapid response flood hazard maps by taking the existing topobathymetric digital elevation model (TBDEM) and raising water elevations based on forecasted water levels. These maps helped to guide emergency response to the storm.

A map showing total water levels and high water marks in Elim, Alaska, after Typhoon Merbok
Map showing total water levels (TWL) and high water marks (HWM) measured in Elim, Alaska, after Extratropical Typhoon Merbok.
2. Coordinating high water mark data and inputting into the USGS Flood Event Viewer 

High water mark (HWM) data are used by agencies such as the Federal Emergency Management Agency (FEMA) to prioritize disaster relief funding. These data are also used to validate flood models.

After Extratropical Typhoon Merbok struck western Alaska, HWM data were collected by the State of Alaska Department of Natural Resources, USGS, University of Alaska, Fairbanks, USDA-NRCS, and private engineering and surveying firms. Athena Clark and Lauren Privette (USGS Coastal Storm Team) facilitated data incorporation into the USGS Flood Event Viewer, with assistance from Alex Nereson. Chris Zimmerman and John Reed of the USGS Alaska Science Center assisted with data management and data entry. 

The USGS Flood Viewer previously did not cover Alaska; the Extratropical Typhoon Merbok HWM data is the first data from the Alaska coast to be incorporated into the tool.

3. Assessing the magnitude of coastal erosion caused by Merbok 

Post-storm aerial photography is a critical tool to assess coastal change after storms. When processed into orthomosaics and elevation models, these data can accurately measure the impacts of flooding and coastal erosion. FEMA plans to use these data as one of the factors to prioritize disaster relief funding for communities impacted by Extratropical Typhoon Merbok.

After the storm, staff from the National Park Service acquired aerial imagery along the coast of Norton Sound, which was later processed at the Pacific Coastal and Marine Science Center. It will be compared to best available pre-storm imagery and elevation surfaces to map and quantify coastal erosion and damage to coastal protection structures.

Many agencies partnered to make the data collection happen, including NPS, NOAA, USGS, and Alaska DNR. USGS Geologist Andy Ritchie is leading the structure-from-motion image processing. Ann Gibbs, Alex Snyder and Alex Nereson will lead the erosion assessment, with anticipated data delivery in the spring/early summer 2023.

More information detailing the storm impacts and response can be found in this StoryMap.

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