Accession Number : ADA242633

Title :   A Comparison of Manual and Automated Methods for Delimiting Watersheds for Use with GRASS/GIS Software

Descriptive Note : Final rept.,

Corporate Author : ARKANSAS UNIV FAYETTEVILLE

Personal Author(s) : Lockhart, J J

Full Text : http://www.dtic.mil/dtic/tr/fulltext/u2/a242633.pdf

Report Date : Sep 1991

Pagination or Media Count : 31

Abstract : The Geographic Resources Analysis Support System (GRASS) is a geographic information and image processing system originally designed to serve land managers and environmental planners at Army installations. Among the newer automated processes performed by GRASS is the digital computation of watersheds. This report compares the GRASS version 3.0a watershed module with the manual delineation of watersheds, by applying the two methods to installation data taken from Fort Chaffee, Arkansas, a facility with other 72,000 acres of highly variable terrain. This study showed that both methods produced similar results, with some exceptions. In areas of pronounced relief, 7.5-minute data and 1- degree data did produce watersheds, but did not indicate subtle saddle-based boundaries. At the installation scale, the 1-degree data produced adequate major watershed delineation, but was not adequate to determine minor watersheds. The more accurate 7.5-minute data produced a large number of subbasins. The automated method produced good subwatershed basin delineation in areas of greater relief, but unsatisfactory delineation in areas of moderate to lower relief.

Descriptors :   *COMPUTER PROGRAMS , DIGITAL SYSTEMS , COMPUTATIONS , AUTOMATION , COMPARISON , ARMY FACILITIES , TERRAIN , VARIABLES , SCALE , INSTALLATION , RESOURCES , MANAGEMENT PERSONNEL , MANUAL OPERATION , WATERSHEDS , GEOGRAPHY , LAND AREAS , GRASSES , ARKANSAS , IMAGE PROCESSING

Subject Categories : Cartography and Aerial Photography
      Hydrology, Limnology and Potamology

Distribution Statement : APPROVED FOR PUBLIC RELEASE