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Landslide inventory of the Tongass National Forest Proclamation Boundary. This layer is updated yearly or as new imagery or field data becomes available. Last updated in August 2025. |
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Landslide inventory of the Tongass National Forest Proclamation Boundary. This layer is updated yearly or as new imagery or field data becomes available. Last updated in August 2025. |
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SM.FS.data@usda.gov |
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5000 |
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<DIV STYLE="text-align:Left;"><DIV><P><SPAN>This feature class is a polygon landslide inventory of the Tongass National Forest. The digital version of this inventory was started in the year 2000 and the once-over inventory was completed in 2017. The feature class is updated annually or as new imagery becomes available. Both field and photo interpreted landslides are included. The inventory includes all mass wasting features--including talus slopes, snow avalanche fields, and snow avalanche chutes. Therefore, it may be necessary to exclude some mass wasting features prior to analysis depending on the intended use of the data. Each of these are coded differently in the attributes. Most of the landslide polygons were digitized on the 1998 to 2010 ortho photos in GIS, although some were digitized using imagery taken more recently. All the landslides have been age bracketed within the available photo data sets to estimate date of occurrence. Many of them were age bracketed using air photos back to the 1929 Navy Trimegon photos. All landslides have been dated before or after 1948 imagery and before or after the 1996 to 1998 imagery. There is an associated point feature class that contains the landslide initiation zone approximations. These points only exist for true landslides--debris avalanches, debris torrents, combination debris avalanches/torrents, slumps, rotational failures, and rock fall-initiated failures. The 2023 update included new slides from 2020 imagery on Chichagof Island. The 2024 update included new slides from 2023 imagery of Admiralty, Kupreanof, Mitkof, and Wrangell Islands as well as part of Kuiu Island. The 2025 update included additional slides on Mitkof, Wrangell, Etolin and Revilla Islands and adjacent mainland. The 2025 update also revised fields and some previous entries to record imagery sources and more precise dates of occurrence.</SPAN></P></DIV></DIV> |
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<DIV STYLE="text-align:Left;"><DIV><P><SPAN>The USDA Forest Service makes no warranty, expressed or implied, including the warranties of merchantability and fitness for a particular purpose, nor assumes any legal liability or responsibility for the accuracy, reliability, completeness or utility of these geospatial data, or for the improper or incorrect use of these geospatial data. These geospatial data and related maps or graphics are not legal documents and are not intended to be used as such. The data and maps may not be used to determine title, ownership, legal descriptions or boundaries, legal jurisdiction, or restrictions that may be in place on either public or private land. Natural hazards may or may not be depicted on the data and maps, and users should exercise due caution. The data are dynamic and may change over time. The user is responsible to verify the limitations of the geospatial data and to use the data accordingly.</SPAN></P></DIV></DIV> |
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| title:
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Tongass Landslide Initiation |
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| tags:
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["Avalanche","Landslides","Mass Wasting","Soil","economy","economy","elevation","elevation","environment","environment","geoscientific\u200bInformation","geoscientific\u200bInformation","location","location","planning\u200bCadastre","planning\u200bCadastre","structure","structure","transportation","transportation","utilities\u200bCommunication","utilities\u200bCommunication"] |
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en-US |
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150000000 |
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