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National Severe Storms Laboratory Environmental Protection Agency

Elevation Derivatives for National Applications (EDNA)



EDNA Stage 1 Data Layers

Contours (20K)

Compound Topographic Index (CTI)

File Type: Floating Point
Valid values: 0 – 40.85
Description:The compound topographic index is a quantification of the position of a site in the local landscape. It is often referred to as the steady state wetness index and it is defined as: CTI = ln ( As / tanB ) where 'As' is the specific catchment area expressed as m2 per unit width orthogonal to the flow direction and 'B' is the slope angle

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