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description:
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This is a once-over landslide inventory of the Tongass National Forest. This inventory includes all mass wasting features, including talus slopes, snow avalanche fields, and snow avalanche chutes. Each of these are coded differently in the attributes. It may be necessary to exclude several polygons in this data set when using it to determine landslide rates. Most of these landslide polygons were digitized on the 1998 to 2010 orthophotos in GIS. Many of them were age bracketed using air photos back to the 1929 Navy Trimegon photos. It includes both field and photo interpreted landslides. Not all of the landslides included once-over completed in FY2017 were age bracketed. There is an associated Points feature class (Tongass_Landslide_Initiation) that represents the landslide initiation zone approximations. These points only exist for true landslides: debris avalanches, debris torrents, combination debris avalanches/torrents, slumps, rotation failures, and rock fall-initiated failures. |