ABSTRACT: Scale effects and appropriate DEM Scales for regional scale hydrologic applications.

CGRG Bibliography of Canadian Geomorphology
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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 were 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. The topographic analysis tool 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. The sensitivity of various hydrologic parameters, spatial distribution of the basin and channel networks to aggregation is generally dependent on local and regional hillslope gradients. This places a general constraint on the coarsest DEM resolution allowable for hydrological modeling purposes.

Bibliography of Canadian Geomorphology