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Layer: Topographic Position Index (TPI) (ID: 301)

Parent Layer: Topography

Name: Topographic Position Index (TPI)

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Type: Raster Layer

Geometry Type: null

Description: Landscape shape dictates slope stability in steep terrain by concentrating or dispersing water in the landscape. The TPI is an index that reflects the morphology of the topography. The three basic hydro-geomorphic units useful to assessing debris-flow susceptibility are 1)divergent (convex; positive TPI value); 2) planar (flat; around 0); and 3) convergent (concave; negativeTPI value) slope segments. Debris flows frequently occur in slope depressions, shallow ducts,and gullies that are characterized by terrain concavities. The TPI image was generated by applying the Jenness algorithm that considers the surrounding cells up to a certain distance. We calculated the TPI using varying neighboring radiuses (range: 20m to 500m) and conducted a contingency test to identify the most suitable radius, which was found to to be 100m. TPI ranges in the study area from -145.5 (blue) to 141.5 (red).

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Supported Query Formats: JSON, geoJSON

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