Compound Topographic Index

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The Compound Topographic Index (CTI), commonly referred to as the Wetness Index, is a function of the upstream contributing area and the slope of the landscape. The CTI is calculated using the flow accumulation (FA) layer along with the slope as:

CTI = ln ( FA / tan (slope) )

In areas of no slope, a CTI value is obtained by substituting a slope of 0.001. This value is smaller than the smallest slope obtainable from a 1000 m data set with a 1 m vertical resolution.

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Download HYDRO1k CTI data set for North America as a tar file (34.1 MB)
Download entire HYDRO1k data set for North America as a tar file (174.1 MB)

For further assistance, please contact: Customer Services U.S. Geological Survey Center for Earth Resources Observation and Science (EROS) 47914 252nd Street Sioux Falls, SD 57198-0001 Tel: 800-252-4547 Tel: 605-594-6151 Fax: 605-594-6589 Email: custserv@usgs.gov Business Hours: Monday thru Friday, 8:00 a.m. to 4:00 p.m., central time

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U.S. Department of the Interior | U.S. Geological Survey URL: http://eros.usgs.gov/ Page Contact Information: custserv@usgs.gov Page Last Modified: August 22, 2006

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