Flow Direction

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The flow direction data set, like all of the other raster data sets, has been derived from the hydrologically correct DEM. It defines the direction of flow from each cell to its steepest down-slope neighbor. Values of flow direction vary from 1 to 255. Defined flow directions follow the convention adopted by ARC/INFO's flow direction implementation:

32	64	128
16		1
8	4	2

Cells with undefined direction of flow represent sinks and have flow directions that are simple combinations of its neighbors' flow direction values. (See ESRI documentation). Generation of basins and stream networks requires the flow direction data set.

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Download HYDRO1k Flow Direction data set for Africa as a tar file (12.2 MB)
Download entire HYDRO1k data set for Africa as a tar file (215.5 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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