CGRG Bibliography of Canadian Geomorphology
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Author : Armstrong, R.; and Martz, L.W.
Date : 2002.
Title : Topographic parameterization in continental hydrology: a study in scale.
Publication : Annual Meeting of the Canadian Geophysical Union. May 18-21, 2002, Banff, Alberta.
Issue :
Page(s) :
Abstract
Digital elevation models (DEMs) are useful and popular tools from which topographic parameters can be quickly and efficiently extracted for various hydrologic applications. DEMs coupled with automated methods for extracting topographic information provide a powerful means of parameterizing hydrologic models over a wide range of scales. However, choosing an appropriate DEM scale for particular hydrologic modeling applications is limited by a lack of understanding of the effects of scale and grid resolution on land-surface representation. The scale effects of aggregation on square-grid DEMs of two continental scale basins (Mackenzie- and Missouri River) and several nested sub-basins are examined. The base DEMs are extracted from the HYDRO1k DEM of North America, which has a nominal resolution of 1km. Successively coarser grids of 2, 4, 8, ...64km were generated from the ‘base’ DEMs using simple linear averaging. 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 scales or resolutions. The effects of changing DEM resolution are examined by considering changes in the spatial distribution and statistical properties of selected topographic variables of hydrological importance. Results of this research show basin delineation and parameter values to be unreliable below a mean hydraulic slope of about 1%, with some notable exceptions. For the basins of this study, a mean slope of 1% is generally observed at DEM resolutions of 8km and 16km respectively. This suggests the existence of a threshold between the mean hydraulic slope of a basin and the reproduction of important drainage features with acceptable losses in accuracy. Based on the results of this study, it is recommended that a grid size of less than or equal to about 10km be used when performing watershed parameterizations for continental scale hydrologic applications.
Bibliography of Canadian Geomorphology