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United States Department of Agriculture

Agricultural Research Service


item Garbrecht, Jurgen
item Martz, Lawrence

Submitted to: Grazinglands Research Laboratory Miscellaneous Publication
Publication Type: Government Publication
Publication Acceptance Date: 11/16/2004
Publication Date: 12/1/2004
Citation: Garbrecht, J.D., Martz, L.W., 2004. TOPAZ Overview Manual-Updated Manual. Grazinglands Research Laboratory Miscellaneous Publication. Available:

Interpretive Summary: The layout of the land surface is often needed for water resources, runoff, erosion, water quality, and soil and water conservation investigations. Traditionally the layout was determined by time consuming and resource intensive surveys. A software tool was developed by the USDA, Agricultural Research Service, Grazinglands Research Laboratory, El Reno, Oklahoma, to automate the process of identifying the location of streams, drainage boundaries, land-surface slope, etc. with the help of a computer and digital maps of the land surface. The name of the software tool that performs the land surface analysis is TOPAZ (TOpographical PArameteriZation). This Overview Manual provides a summary of the software features, input data, computer requirements, capabilities and limitations, and software organization. It also describes in general terms the methods used to extract the land-surface information from the digital maps.

Technical Abstract: TOPAZ (TOpographic PArameteriZation) is a software package for automated analysis of digital landscape topography. TOPAZ processes a raster digital elevation model (DEM) to identify and measure topographic features; define surface drainage, flow direction and flow paths; subdivide watersheds along drainage divides into subcatchments; quantify the drainage network and calculate channel parameters; and, estimate representative subcatchment parameters. TOPAZ is designed primarily to assist with topographic evaluation and watershed parameterization in support of hydrologic modeling and analysis. The overall objective of TOPAZ is to provide a comprehensive evaluation of the digital landscape topography with particular emphasis on maintaining consistency between all derived data, the initial input topography, and the physics underlying energy and water flux processes at the landscape surface. The purpose of this report is to provide a brief overview of the methods underlying TOPAZ; document limitations and capabilities of the software; describe the organization and operation of TOPAZ; summarize input requirements and output capabilities; and, list available documentation. This TOPAZ Version 3.2 is an upgrade of TOPAZ Version 3.12, which was released in April 1999. Upgrades are primarily the addition of spatially distributed characterization of the channel network parameters and expanded output and interface capabilities that were requested by users.

Last Modified: 06/23/2017
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