Identification_Information:
Citation:
Citation_Information:
Originator: Salisbury, J.B.
Publication_Date: 2024
Title: Landslide hazard susceptibility mapping in Homer, Alaska
Geospatial_Data_Presentation_Form: geodatabase, raster
Series_Information:
Series_Name: Report of Investigation
Issue_Identification: RI 2024-3
Publication_Information:
Publication_Place: Fairbanks, Alaska, United States
Publisher: Alaska Division of Geological & Geophysical Surveys
Other_Citation_Details: 21 p., 3 sheets
Online_Linkage: https://doi.org/10.14509/31155
Description:
Abstract: Landslide hazard susceptibility mapping in Homer, Alaska, Report of Investigation 2024-3, 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 of Homer, Alaska and nearby populated areas including Kachemak City and Millers Landing. The landslide inventory map integrates existing maps of landslides caused by the 1964 Great Alaska Earthquake and newly mapped slope failures identified in sequences of aerial photos since 1950 and high-resolution light detection and ranging (lidar) data collected for this project. The Alaska Division of Geological & Geophysical Surveys (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/10.14509/31155.
Purpose: This study provides a regional evaluation of landslide hazards in and around the City of Homer. The study aims to help the community better understand landslide hazards, inform mitigation efforts, guide future development activities, and protect public safety.
Supplemental_Information:
>scarps_lidar: Feature class containing landslide head scarp lines identified and digitized based on geomorphological characteristics in the high-resolution 2019 lidar data.
>deposits_lidar: Feature class containing polygons outlining the extent of landslide deposits identified in the high-resolution 2019 lidar data.
>deposits_photo: Slope failures identified in georeferenced aerial images.
>runouts: Feature dataset collection of feature classes that provide categorical volume and dimensions of modeled hypothetical debris flow runouts from steep catchments in the Homer area. Runout zones are computed using LaharZ (Iverson and others, 1998; Schilling, 1998), and debris flow material characteristics are from Griswold and Iverson (2008). Volumes for runout zone modeling were estimated per catchment based on percentages (5, 10, 25 percent) of the total volume of topsoil in the catchment, as well as the percentage of catchment identified as having sustained slope failure in the historical period. Estimated points beyond which sediments are deposited are based on the geomorphological characteristics of each catchment.
>FOS-5m: Raster image data model of the relationship between shear forces acting to move material downslope and forces acting to resist downslope movement. This model was used as a proxy for shallow landslide susceptibility.
Time_Period_of_Content:
Time_Period_Information:
Multiple_Dates/Times:
Single_Date/Time:
Calendar_Date: 1964
Single_Date/Time:
Calendar_Date: 2023
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -151.732814
East_Bounding_Coordinate: -151.372943
North_Bounding_Coordinate: 59.709401
South_Bounding_Coordinate: 59.598718
Keywords:
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificInformation
Theme:
Theme_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys
Theme_Keyword: Coastal
Theme_Keyword: Coastal and River
Theme_Keyword: Colluvium
Theme_Keyword: DGGS
Theme_Keyword: Debris Avalanche
Theme_Keyword: Debris Flow
Theme_Keyword: Debris Flow Deposit
Theme_Keyword: Earthquake Related Slope Failure
Theme_Keyword: Engineering
Theme_Keyword: Engineering Geology
Theme_Keyword: Environment
Theme_Keyword: Environmental
Theme_Keyword: Geologic
Theme_Keyword: Geologic Hazards
Theme_Keyword: Geological Process
Theme_Keyword: Geology
Theme_Keyword: Geomorphology
Theme_Keyword: Geotechnical
Theme_Keyword: Hazards
Theme_Keyword: Hydrology and Surficial Geology
Theme_Keyword: Landslide
Theme_Keyword: LiDAR
Theme_Keyword: Modeling
Theme_Keyword: Raster Image
Theme_Keyword: Slope
Theme_Keyword: Slope Instability
Theme_Keyword: Surface
Theme_Keyword: Surface Water
Theme_Keyword: Surficial
Theme_Keyword: Surficial Geology
Place:
Place_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys
Place_Keyword: Bear Canyon
Place_Keyword: Beluga Lake
Place_Keyword: Bidarki Creek
Place_Keyword: Bluff Point
Place_Keyword: Bridge Creek
Place_Keyword: Bridge Creek Reservoir
Place_Keyword: City of Homer
Place_Keyword: City of Kachemak
Place_Keyword: Coal Point
Place_Keyword: Cook Inlet
Place_Keyword: Crossman Ridge
Place_Keyword: Diamond Creek
Place_Keyword: Diamond Gulch
Place_Keyword: Diamond Ridge
Place_Keyword: Homer
Place_Keyword: Homer Spit
Place_Keyword: Kachemak Bay
Place_Keyword: Kachemak City
Place_Keyword: Lampert Lake
Place_Keyword: Mud Bay
Place_Keyword: Neilson Canyon
Place_Keyword: Palmer Creek
Place_Keyword: Sterling Highway
Place_Keyword: Twitter Creek
Place_Keyword: Waterman Canyon
Place_Keyword: Woodard Canyon
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).
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.
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Alaska Division of Geological & Geophysical Surveys
Contact_Position: Metadata Manager
Contact_Address:
Address_Type: mailing and physical
Address: 3354 College Road
City: Fairbanks
State_or_Province: AK
Postal_Code: 99709-3707
Country: USA
Contact_Voice_Telephone: (907)451-5020
Contact_Facsimile_Telephone: (907)451-5050
Contact_Electronic_Mail_Address: dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Contact_Instructions: 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.
Data_Set_Credit: DGGS collected and processed lidar for use in this landslide hazard resiliency project for the City of Homer, funded by the Federal Emergency Management Agency (FEMA) through Cooperating Technical Partnership (CTP) with the City of Homer and DGGS under federal grant number CTP EMS-2018- CA-00016-S01. DGGS thanks the Homer Planning Commission for guidance throughout the multi-year project and Jonathan Godt, Rich Buzard, and Bretwood Higman for constructive reviews that significantly improved this manuscript. We also thank Amy Macpherson for GIS support and Kristen Janssen for designing the report layout.
Cross_Reference:
Citation_Information:
Originator: Buzard, R.M.
Publication_Date: 2021
Title: Photogrammetry-derived historical orthoimagery for Homer, Alaska from 1951, 1952, 1964, and 1985
Series_Information:
Series_Name: Raw Data File
Issue_Identification: RDF 2021-21
Publication_Information:
Publication_Place: Fairbanks, Alaska, United States
Publisher: Alaska Division of Geological & Geophysical Surveys
Other_Citation_Details: 10 p
Online_Linkage: https://doi.org/10.14509/30824
Cross_Reference:
Citation_Information:
Originator: Buzard, R.M.
Originator: Overbeck, J.R.
Publication_Date: 2022
Title: Coastal bluff stability assessment for Homer, Alaska
Series_Information:
Series_Name: Report of Investigation
Issue_Identification: RI 2022-5
Publication_Information:
Publication_Place: Fairbanks, Alaska, United States
Publisher: Alaska Division of Geological & Geophysical Surveys
Other_Citation_Details: 22 p., 2 sheets, scale 1:50,000
Online_Linkage: https://doi.org/10.14509/30908
Cross_Reference:
Citation_Information:
Originator: Reger, R.D.
Publication_Date: 1978
Title: Bluff Point landslide, a massive ancient rock failure near Homer, Alaska
Series_Information:
Series_Name: Geologic Report
Issue_Identification: GR 61B
Publication_Information:
Publication_Place: Fairbanks, Alaska, United States
Publisher: Alaska Division of Geological & Geophysical Surveys
Other_Citation_Details: p. 5-9
Online_Linkage: https://doi.org/10.14509/409
Cross_Reference:
Citation_Information:
Originator: Salisbury, J.B.
Originator: Daanen, R.P.
Originator: Herbst, A.M.
Publication_Date: 2021
Title: Lidar-derived elevation models for Homer, Alaska
Series_Information:
Series_Name: Raw Data File
Issue_Identification: RDF 2021-2
Publication_Information:
Publication_Place: Fairbanks, Alaska, United States
Publisher: Alaska Division of Geological & Geophysical Surveys
Other_Citation_Details: 6 p
Online_Linkage: https://doi.org/10.14509/30591
Cross_Reference:
Citation_Information:
Originator: Suleimani, E.N.
Originator: Nicolsky, D.J.
Originator: Salisbury, J.B.
Publication_Date: 2019
Title: Updated tsunami inundation maps for Homer and Seldovia, Alaska
Series_Information:
Series_Name: Report of Investigation
Issue_Identification: RI 2018-5 v. 2
Publication_Information:
Publication_Place: Fairbanks, Alaska, United States
Publisher: Alaska Division of Geological & Geophysical Surveys
Other_Citation_Details: 97 p., 11 sheets
Online_Linkage: https://doi.org/10.14509/30095
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report: 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 in and around Homer, 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.
Logical_Consistency_Report: Not applicable
Completeness_Report: This data release is complete.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report: DGGS used lidar point cloud data to produce a high-resolution (1.6 ft [0.5 m]) digital terrain model (DTM) and a digital surface model (DSM) for Homer (Salisbury and others, 2021). 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. The positional accuracy 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.
Lineage:
Process_Step:
Process_Description: Lidar Acquisition and Processing - DGGS used lidar point cloud data to produce a high-resolution (1.6 ft [0.5 m]) digital terrain model (DTM) and a digital surface model (DSM) for Homer (Salisbury and others, 2021). 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.
Process_Date: 2019
Process_Step:
Process_Description: Landslide Inventory - The comprehensive landslide inventory presented here spans 1952-2019 and was generated by (1) collecting and organizing existing information about previously identified landslides; (2) obtaining, georeferencing, and analyzing sets of aerial photographs since 1952; (3) acquiring, processing, and analyzing high-resolution lidar elevation data; (4) compiling all landslide information into a geodatabase; and (5) generating a landslide inventory map.
Process_Date: 2021
Process_Step:
Process_Description: Shallow Landslide Susceptibility - We estimated the FOS for shallow landslides, or earthflows, that are approximately the thickness of the mapped soil column (~5 ft [1.25 m] or less, USDA NRCS, 2005). Data were processed using methods described in the accompanying report.
Process_Date: 2021
Process_Step:
Process_Description: Deep-Seated Landslide Susceptibility - Deep-seated landslides involve the failure of materials, as the name implies, several tens of feet below layers of active soil and the uppermost weathered bedrock in an area. We estimated the FOS for Deep-seated landslides using methods described in the accompanying report.
Process_Date: 2021
Process_Step:
Process_Description: Debris Flow Runout Modeling - We used LaharZ, a computer model developed by Schilling (1998) for the U.S. Geological Survey, to simulate the behavior and forecast areas likely to be inundated by hypothetical future debris flow events. For all hypothetical runouts, we used ArcGIS Pro focal statistics and conditional tools to smooth the results.
Process_Date: 2021
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: raster
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 5
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.999600
Longitude_of_Central_Meridian: -153
Latitude_of_Projection_Origin: 0
False_Easting: 500000.000000
False_Northing: 0
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: .00000001
Ordinate_Resolution: .00000001
Planar_Distance_Units: Meters
Geodetic_Model:
Horizontal_Datum_Name: NAD83 (2011)
Ellipsoid_Name: GRS 80
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257222101
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: scarps_lidar
Entity_Type_Definition: Feature class containing landslide head scarp lines identified and digitized based on geomorphological characteristics in the high-resolution 2019 lidar data.
Entity_Type_Definition_Source: DGGS
Entity_Attribute_Layer_Name: scarps_lidar
Attribute:
Attribute_Label: Age
Attribute_Definition: Estimated year of occurrence of mapped landslides, if applicable. Known 1964 landslide scarps are those that are identified in the geomorphology that are coincident with post-1964 landslides mapped by Waller, 1966.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: text
Attribute:
Attribute_Label: Name
Attribute_Definition: Mostly N/A, except for the deep-seated Bluff Point landslide.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: text
Attribute:
Attribute_Label: Shape_Length
Attribute_Definition: Geodesic length of digitized headscarp line in meters.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Attribute:
Attribute_Label: Scarp_Type
Attribute_Definition: Denotes whether a feature is a landslide head scarp or an intermediate scarp (a scarp within a landslide body.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: text
Detailed_Description:
Entity_Type:
Entity_Type_Label: deposits_lidar
Entity_Type_Definition: Feature class containing polygons outlining the extent of landslide deposits identified in the high-resolution 2019 lidar data.
Entity_Type_Definition_Source: DGGS
Entity_Attribute_Layer_Name: deposits_lidar
Attribute:
Attribute_Label: Age
Attribute_Definition: Estimated year of occurrence of mapped landslide deposits, if applicable. Known 1964 landslide deposits are those that are identified in the geomorphology that are coincident with post-1964 landslides mapped by Waller, 1966.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: text
Attribute:
Attribute_Label: Shape_Length
Attribute_Definition: Geodesic length of landslide deposit perimeter in meters
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Attribute:
Attribute_Label: Shape_Area
Attribute_Definition: Geodesic area of landslide deposit polygon in square meters
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Detailed_Description:
Entity_Type:
Entity_Type_Label: deposits_photo
Entity_Type_Definition: Slope failures identified in georeferenced aerial images.
Entity_Type_Definition_Source: DGGS
Entity_Attribute_Layer_Name: deposits_photo
Attribute:
Attribute_Label: Age
Attribute_Definition: Date range during which the slope failure occurred, based on collection dates of various sets of aerial images.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: text
Attribute:
Attribute_Label: Shape_Length
Attribute_Definition: Geodesic length of landslide deposit perimeter in meters.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Attribute:
Attribute_Label: Shape_Area
Attribute_Definition: Geodesic area of landslide deposit polygon in square meters.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Detailed_Description:
Entity_Type:
Entity_Type_Label: runouts
Entity_Type_Definition: Feature dataset collection of feature classes that provide categorical volume and dimensions of modeled hypothetical debris flow runouts from steep catchments in the Homer area. Runout zones are computed using LaharZ (Iverson and others, 1998; Schilling, 1998), and debris flow material characteristics are from Griswold and Iverson (2008). Volumes for runout zone modeling were estimated per catchment based on percentages (5, 10, 25 percent) of the total volume of topsoil in the catchment, as well as the percentage of catchment identified as having sustained slope failure in the historical period. Estimated points beyond which sediments are deposited are based on the geomorphological characteristics of each catchment.
Entity_Type_Definition_Source: DGGS
Entity_Attribute_Layer_Name: runouts
Attribute:
Attribute_Label: Value
Attribute_Definition: Calculated volumes for runout zone modeling. The values are estimated per catchment and based on percentages (5, 10, 25% or "map" which is the volume of soil mapped in shallow landslides since 1952) of the total volume of topsoil in the catchment, as well as the percentage of catchment identified as having sustained slope failure in the historical period.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Attribute:
Attribute_Label: Shape_Length
Attribute_Definition: Geodesic length of modeled hypothetical debris flow runout perimeter in meters.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Attribute:
Attribute_Label: Shape_Area
Attribute_Definition: Geodesic area of modeled hypothetical debris flow runout polygon in square meters.
Attribute_Definition_Source: this report
Attribute_Domain_Values:
Unrepresentable_Domain: number
Detailed_Description:
Entity_Type:
Entity_Type_Label: ri2024-3-homer-ls-hz-FOS-5m.tif
Entity_Type_Definition: Raster image data model of the relationship between shear forces acting to move material downslope and forces acting to resist downslope movement. This model was used as a proxy for shallow landslide susceptibility.
Entity_Type_Definition_Source: DGGS
Entity_Attribute_Layer_Name: FOS-5m
Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Alaska Division of Geological & Geophysical Surveys
Contact_Position: Metadata Manager
Contact_Address:
Address_Type: mailing and physical
Address: 3354 College Road
City: Fairbanks
State_or_Province: AK
Postal_Code: 99709-3707
Country: USA
Contact_Voice_Telephone: (907)451-5020
Contact_Facsimile_Telephone: (907)451-5050
Contact_Electronic_Mail_Address: dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Contact_Instructions: 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.
Resource_Description: RI 2024-3
Distribution_Liability: 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.
Standard_Order_Process:
Non-digital_Form: DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.
Fees: Contact DGGS for current pricing
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: geodatabase, raster
Format_Version_Date: 20240405
Format_Information_Content: digital data
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: https://doi.org/10.14509/31155
Fees: Free download
Metadata_Reference_Information:
Metadata_Date: 20240405
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Alaska Division of Geological & Geophysical Surveys
Contact_Person: Simone Montayne
Contact_Position: Metadata Manager
Contact_Address:
Address_Type: mailing and physical
Address: 3354 College Road
City: Fairbanks
State_or_Province: AK
Postal_Code: 99709-3707
Country: USA
Contact_Voice_Telephone: (907)451-5020
Contact_Facsimile_Telephone: (907)451-5050
Contact_Electronic_Mail_Address: dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Use_Constraints: 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.
Metadata_Extensions:
Online_Linkage: https://dggs.alaska.gov/metadata/dggs.ext
Profile_Name: dggs metadata extensions