CGRG Bibliography of Canadian Geomorphology
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Author : Armstrong, R.; and Martz, L.W.
Date : 2003.
Title : Grid size and topographic parameterization.
Publication : Canadian Geophysical Union. Annual Meeting, May 10 -14, 2003. Banff Centre, Banff, Alberta.
Issue :
Page(s) :
Abstract
In a recent study, it was shown that simply aggregating digital elevation data can have a severe affect on the delineation of drainage basins, channel networks and derived topographic variables. As a result, the potential for rescaling DEMs via grid cell aggregation to provide physiographic data (e.g., drainage basins, channel networks and topographic variables) for hydrologic applications in large basins, is limited. This study expands on the earlier research which involved topographic analysis of the Mackenzie and Missouri River basins, to include the Wolf Creek Research Basin (located in the Yukon Territory, Canada) and the Wabasca River (located in Alberta, Canada). Several coarser grid sizes are produced from source DEMs of Wolf Creek (15 m resolution) and the Wabasca River (200 m), using simple averaging. As in the original study, TOPAZ (Topographic Parameterization) was applied to the base- and aggregated DEMs using constant critical source area (CSA) and minimum source channel length (MSCL) values to extract topographic variables at varying grid resolutions. The effects of increasing grid size are examined by considering changes in the spatial distribution and statistical properties of several topographic variables. In this study, the relationship between valley width and grid size, grid size and drainage basin area, and grid size and CSA is also examined. Results obtained in this study, are similar to those obtained in the original study. Results also suggest that grid sizes should be less than 0.03 % of the total basin area. It is also suggested that grid sizes should be less than 10 % of the CSA value used. Interestingly, the results show no evidence of a direct relationship between valley width and grid size with significant changes in network configuration. The results, in general, are considered to be a product of elevation errors produced through averaging of the elevation data rather than a result of the CSA and MSCL values used.
Bibliography of Canadian Geomorphology