Landslide hazard susceptibility mapping in Haines, Alaska

Nicolazzo, J.A. Larsen, M.C. 2025 Landslide hazard susceptibility mapping in Haines, Alaska geodatabase, raster Report of Investigation RI 2024-8 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 16 p., 3 sheets, scale 1:25,000 https://doi.org/10.14509/31309 Landslide hazard susceptibility mapping in Haines, Alaska, Report of Investigation 2024-8, provides a map and database of historical and prehistoric slope failures, maps of shallow and deep-seated landslide susceptibility, and a map of simulated debris flow runouts for the city and borough of Haines, Alaska. This work was prompted by the deadly Beach Road landslide that occurred on December 2, 2020, in Haines, Alaska, which highlights the significant safety and financial risks posed by slope failures to people and infrastructure. To better inform the Haines Borough of their potential landslide hazards and increase the city's hazard resiliency, the Alaska Division of Geological & Geophysical Surveys (DGGS) developed maps of historical and prehistorical slope failures, shallow landslide susceptibility, and modeled debris flow runouts. DGGS staff created a shallow landslide susceptibility map following protocols like those developed by the Oregon Department of Geology and Mineral Industries, which includes incorporating landslide inventory data, geotechnical soil properties, and lidar-derived topographic slope to calculate the Factor of Safety (FOS), which serves as a proxy for landslide susceptibility. Debris flow runout extents were generated using the model Laharz, which simulates runout extents based on catchment-specific physical parameters (e.g., hypothetical sediment volumes). Data from these analyses are collectively intended to depict locations where landslides are relatively more likely to occur or are relatively more likely to travel. The results provide important hazard information that can help guide planning and future risk investigations. The maps are not intended to predict slope failures and are site-specific; detailed investigations should be conducted before development in vulnerable areas. Results are for informational purposes and are not intended for legal, engineering, or surveying uses. These data and the interpretive maps and report are available from the DGGS website: http://doi.org/10.14509/31309. The deadly Beach Road landslide that occurred on December 2, 2020, in Haines, Alaska, highlights the significant safety and financial risks posed by slope failures to people and infrastructure. To better inform the Haines Borough of their potential landslide hazards and increase the city's hazard resiliency, the Alaska Division of Geological & Geophysical Surveys (DGGS) developed maps of historical and prehistorical slope failures, shallow landslide susceptibility, and modeled debris flow runouts. >landslide-susceptibility: Landslide inventory geodatabase and accompanying data dictionary >shallow_landslide-susceptibility: Raster image depicting slopes susceptible to shallow landslides 1972 2024 ground condition Complete None planned -135.756590 -135.291554 59.405233 59.083205 ISO 19115 Topic Category geoscientificInformation Alaska Division of Geological & Geophysical Surveys Coastal Coastal and River Colluvial Deposits Colluvium DGGS Debris Avalanche Debris Flow Debris Flow Deposit Drainage Patterns Emergency Preparedness Engineering Engineering Geology Environmental Geologic Geologic Hazards Geological Process Geology Geomorphology Geotechnical Hazards Landslide Landslide Deposit Landslide Susceptibility Modeling Rock Avalanche Rockfall Rocks Rotational Landslide Slides Slope Slope Instability Soils Surface Surface Water Surficial Surficial Geology Translational Landslide Transportation Corridor Unconsolidated Deposits Alaska Division of Geological & Geophysical Surveys Chilkat Peninsula Chilkat River Chilkat State Park Chilkoot Lake Ferebee River Haines Haines Borough Johnson Creek Lily Lake Mink Creek Mount Ripinski Mud Bay Nahku Portage Shakuseyi Creek Shiyi Bay Southeast Alaska Takhin River Yindastuki Walker, J.D., Geissman, J.W., Bowring, S.A, and Babcock, L.E., comp., 2012, Geologic Time Scale v. 4.0: Geological Society of America Holocene This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below). Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product. Alaska Division of Geological & Geophysical Surveys Metadata Manager mailing and physical

3354 College Road

Fairbanks AK 99709-3707 USA (907)451-5020 (907)451-5050 dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible. DGGS collected and processed lidar data and conducted landslide susceptibility mapping for this project using funds provided by the Federal Emergency Management Agency (FEMA) Cooperative Technical Partnership (CTP) Program grant number CTP EMS-2021-CA-00013-S01. We thank our reviewers Katreen Wikstrom Jones (DGGS) and Jacqueline Foss (U.S. Forest Service) for their thoughtful comments that helped improve the quality of this product. We also appreciate DOT&PF engineer Travis Eckhoff, P.E., for his local knowledge that helped verify our models, and Dr. Margaret Darrow (University of Alaska Fairbanks) for her insight into the Beach Road landslide. We also acknowledge Victoria Nelson for her countless hours spent performing soil laboratory testing and mapping landslide scarps in support of this project while working on her master's thesis. Daanen, R.P. Herbst, A.M. Wikstrom Jones, K.M. Wolken, G.J. 2021 High-resolution lidar data for Haines, southcentral Alaska, December 8-12, 2020 Raw Data File RDF 2021-4 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 8 p https://doi.org/10.14509/30595 Nicolazzo, J.A. Darrow, M.M. Larsen, M.C. Walser, S.L. 2024 Rock strength properties of the Haines-Takshanuk Mountains-Chilkat Peninsula area STATEMAP project, Southeast Alaska Raw Data File RDF 2024-28 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 4 p https://doi.org/10.14509/31416 Nicolazzo, J.A. Darrow, M.M. Walser, S.L. 2024 Soil index properties and radiocarbon ages of the Haines-Takshanuk Mountains-Chilkat Peninsula area STATEMAP project, Southeast Alaska Raw Data File RDF 2024-27 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 24 p https://doi.org/10.14509/31415 Nicolazzo, J.A. Larsen, M.C. 2024 Lidar interpretation in Haines, Alaska (poster): Haines Borough community meeting, September 4, 2024 Poster and Presentation Nicolazzo, J.A. and Larsen, M.C., 2024 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 1 sheet https://doi.org/10.14509/31414 Nicolsky, D.J. Suleimani, E.N. Salisbury, J.B. 2018 Tsunami inundation maps for Skagway and Haines, Alaska Report of Investigation RI 2018-2 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 69 p., 3 sheets https://doi.org/10.14509/30029 Truskowski, C.M. Walser, S.L. Larsen, M.C. Nicolazzo, J.A. Gillis, R.J. Bull, K.F. Regan, S.P. Darrow, M.M. Montayne, Simone 2024 Field station locations and data for the geologic map of the Haines-Takshanuk Mountains-Chilkat Peninsula area STATEMAP project, southeast Alaska, collected in 2022 and 2023 Raw Data File RDF 2024-17 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 3 p https://doi.org/10.14509/31285 Wolken, G.J. Wikstrom Jones, K.M. Whorton, E.N. Gould, A.I. Hendricks, M.D. 2017 Photogrammetric data of the Haines Highway corridor: May 26, 2014 Raw Data File RDF 2017-6 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 20 p https://doi.org/10.14509/29736 Zechmann, J.M. Daanen, R.P. Wikstrom Jones, K.M. Wolken, G.J. 2024 Lidar-derived elevation data for Haines, Southeast Alaska, collected October 2021 and October 2022 Raw Data File RDF 2023-18 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 16 p https://doi.org/10.14509/31034 The slope failure inventory, shallow landslide susceptibility, modeled debris flow runout map, and integrated results maps were developed using the best available data; however, there are inherent limitations. The intended use of these data products is to help identify the relative slope failure risk, provide a basis for regional planning and increased resiliency, and help identify localities where more detailed slope failure hazard mapping is warranted. Maps are not intended for use at scales other than the published map data scale. The accompanying report provides a complete list of specific limitations and potential sources of error. Not applicable This data release is complete. The positional accuracy of the slope failure inventory, factor of safety, debris flow runout models were developed using the best available data; however, there are inherent limitations to the calculated and interpreted feature extents. The accompanying report provides a complete discussion of specific limitations and potential sources of error. For most of the project area DGGS used lidar point cloud data to produce a high-resolution (1-3ft) digital terrain models (DTM). The DTM, also known as a bare-earth elevation model, was essential for identifying landslide geomorphology beneath dense vegetation, confirming evidence of landslide activity identified in aerial photograph sequences, making FOS calculations, and modeling potential debris flow runouts. For the area around Chilkoot Lake where lidar was not collected, we downloaded data from ArcticDEM. The ArcticDEM is a composite of numerous digital elevation models (DEMs) sourced from satellite imagery collected over several years. It has 2-m (about 6-ft) resolution and contains more elevation spikes, pits, and holes of missing data than our datasets; therefore, all results from the ArcticDEM dataset have lower confidence. Lidar acquisition and processing - Two light detection and ranging (lidar) datasets were previously collected for other projects in the Haines area that overlap this project's AOI. Quantum Spatial collected one dataset in May 2014 (1-m [3-ft] resolution) that was centered primarily on the city of Haines. In December 2020, DGGS collected lidar as part of emergency operations following the landslide event. The collection covered areas over the city of Haines, south along Mud Bay Road, extents of existing lidar datasets displayed over Esri's World Terrain basemap of the area of interest. North along Lutak Road, and on the opposite side of Lutak Inlet with a 1-m (3-ft) resolution. Additionally, during 2021 and 2022, DGGS collected a new lidar dataset for this project, which covered a much larger area with a 50-cm (1.5 ft) resolution. This project used digital terrain models (DTMs) generated from each of these lidar datasets. For the area around Chilkoot Lake where lidar was not collected, we downloaded data from ArcticDEM. The ArcticDEM is a composite of numerous digital elevation models (DEMs) sourced from satellite imagery collected over several years. It has 2-m (6-ft) resolution and contains more elevation spikes, pits, and holes of missing data than our datasets; therefore, all results from the ArcticDEM dataset have lower confidence. 2023 Landslide inventory - The comprehensive landslide inventory was generated by collecting and organizing existing information about previously identified landslides, acquiring, processing, and analyzing high-resolution lidar elevation data, and compiling all landslide information into a geodatabase. 2023 Shallow landslide susceptibility - We developed a map showing slopes susceptible to shallow landslides. Shallow landslides occur in surficial soils, to a maximum depth of about 4.5 m (15 ft). This method combines areas of mapped shallow landslides with a calculated factor of safety (FOS). The result is a map that displays susceptibility as high, moderate, or low zones. Data were processed using methods described in the accompanying report. 2023 Channelized debris flow susceptibility - We used the methodology of Burns and others (2022) to map slopes that are susceptible to channelized debris flows which includes custom ArcGIS geoprocessing tools to simplify the process. This method models debris flow initiation potential, transport potential, and inundation (deposition) to produce a map that displays debris flow initiation and transport susceptibility in high, moderate, or low zones, and the inundation extent for each level of modeled event severity. The accompanying report provides details of the proceedure. 2023 vector Alaska Albers 55.0 65.0 -154.0 50.0 0 0 coordinate pair 0.0000000030536018158500163 0.0000000030536018158500163 meters NAD83 GRS 80 6378137 298.257222101 ri2024-8-haines-landslide-susceptibility.gdb, ri2024-8-haines-landslide-susceptibility-data-dictionary.xlsx Landslide inventory geodatabase and accompanying data dictionary DGGS landslide-susceptibility ri2024-8-shallow_landslide-susceptibility.tif Raster image depicting slopes susceptible to shallow landslides DGGS shallow_landslide-susceptibility Alaska Division of Geological & Geophysical Surveys Metadata Manager mailing and physical

3354 College Road

Fairbanks AK 99709-3707 USA (907)451-5020 (907)451-5050 dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the Alaska Department of Natural Resources or Division of Geological & Geophysical Surveys. https://dggs.alaska.gov/metadata/dggs.ext dggs metadata extensions