Debris flow hazard evaluations for multi-hazard risk mapping in Sitka, Alaska

Debris flow hazard evaluations for multi-hazard risk mapping in Sitka, Alaska, Report of Investigation 2024-2, provides digital data used to develop interpretive maps and a geospatial database of historical debris flows, shallow-debris flow susceptible slopes, and simulated debris flow runouts for the City of Sitka, Alaska. On August 18, 2015, heavy rainfall and wind resulted in numerous debris flows in and around Sitka, Alaska. Four debris flows impacted roads and infrastructure in Sitka, and the southernmost of two flows at Kramer Avenue took the lives of three residents. In response to these events, the Alaska Division of Geological & Geophysical Surveys (DGGS), through a Community and Technical Partners Grant with the Federal Emergency Management Agency (FEMA), initiated a multi-hazard assessment of the Sitka area. The objective was to help better understand debris flow hazards, inform mitigation efforts, guide future development activities, and protect public safety in and around Sitka. We emphasize this study is a regional evaluation, not a site-specific assessment. It would be inappropriate to use the results for site-specific decision-making. Our final products show what computer models predict could occur based on the selected inputs and with the idealized assumption that the simplified input conditions occur, unvaryingly, throughout the entire model area. The reality is much more complex and can only be addressed with detailed site-specific studies. Our model is intentionally conservative to not underestimate the potential risk to life and safety, and this can be seen in areas where modeled potential debris flow runouts are longer than those observed from historic debris flows. These data and the interpretive maps and report are available from the DGGS website: http://doi.org/10.14509/30187.

Data and Resources

Field Value
access_constraints ["Use Constraints: 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.", "Access Constraints: 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)."]
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contact-email dggspubs@alaska.gov
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licence ["The State of Alaska makes no expressed 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."]
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metadata-date 2025-06-25
metadata-language eng; USA
metadata_type geospatial
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responsible-party [{"name": "Alaska Division of Geological & Geophysical Surveys", "roles": ["pointOfContact"]}]
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Groups
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  • National Provider
  • North America
Tags
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  • AmeriGEOSS
  • CKAN
  • GEO
  • GEOSS
  • National
  • North America
  • United States
  • bear cove
  • beaver lake
  • blue lake
  • cascade creek
  • castle hill
  • coastal
  • coastal and river
  • colluvium
  • crescent bay
  • debris avalanche
  • debris flow
  • debris flow deposit
  • earthquake related slope failure
  • engineering
  • engineering geology
  • environment
  • environmental
  • geologic
  • geologic hazards
  • geological process
  • geology
  • geomorphology
  • geotechnical
  • granite creek
  • green lake
  • halibut point
  • halibut point road
  • harbor mountain road
  • harbor point
  • hazards
  • heart lake
  • herring cove
  • holocene
  • hydrology and surficial geology
  • indian river
  • indian river road
  • indian river valley
  • jamestown bay
  • landslide
  • lidar
  • maksoutoff road
  • medvejie lake
  • modeling
  • raster image
  • sawmill cove
  • sawmill creek
  • sawmill creek road
  • sealing cove
  • silver bay
  • sitka
  • sitka ferry terminal road
  • sitka harbor
  • slope
  • slope instability
  • southeast alaska
  • starrigavan bay
  • surface
  • surface water
  • surficial
  • surficial geology
  • swan lake
  • thimbleberry bay
  • thimbleberry lake
  • thomsen harbor
  • vodopad river
  • whiting harbor
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metadata_created 2025-09-24T11:36:42.373842
metadata_modified 2025-09-24T11:36:42.373855
notes Debris flow hazard evaluations for multi-hazard risk mapping in Sitka, Alaska, Report of Investigation 2024-2, provides digital data used to develop interpretive maps and a geospatial database of historical debris flows, shallow-debris flow susceptible slopes, and simulated debris flow runouts for the City of Sitka, Alaska. On August 18, 2015, heavy rainfall and wind resulted in numerous debris flows in and around Sitka, Alaska. Four debris flows impacted roads and infrastructure in Sitka, and the southernmost of two flows at Kramer Avenue took the lives of three residents. In response to these events, the Alaska Division of Geological & Geophysical Surveys (DGGS), through a Community and Technical Partners Grant with the Federal Emergency Management Agency (FEMA), initiated a multi-hazard assessment of the Sitka area. The objective was to help better understand debris flow hazards, inform mitigation efforts, guide future development activities, and protect public safety in and around Sitka. We emphasize this study is a regional evaluation, not a site-specific assessment. It would be inappropriate to use the results for site-specific decision-making. Our final products show what computer models predict could occur based on the selected inputs and with the idealized assumption that the simplified input conditions occur, unvaryingly, throughout the entire model area. The reality is much more complex and can only be addressed with detailed site-specific studies. Our model is intentionally conservative to not underestimate the potential risk to life and safety, and this can be seen in areas where modeled potential debris flow runouts are longer than those observed from historic debris flows. These data and the interpretive maps and report are available from the DGGS website: http://doi.org/10.14509/30187.
num_resources 4
num_tags 74
title Debris flow hazard evaluations for multi-hazard risk mapping in Sitka, Alaska