Re-scaling river flow direction data from local to continental scales

Abstract

This paper evaluates methods for aggregating detailed flow pattern data extracted from DEM to larger spatial units suitable for representing the hydraulic and routing characteristics of large basins such as the Mackenzie. Five approaches to up-scaling flow data are discussed: simple averaging of DEM elevation data to coarser resolution, drainage enforcement that minimizes impact on the DEM outside the drainage network area, subdivision of drainage basins at various scales while the DEM resolution is held constant, vector averaging of sub-grid flow directions from a higher resolution DEM and a quasi-expert system approach based on the WATFLOOD parameterization scheme. Simple averaging has a profound impact on basin boundaries and flow patterns and cannot be used to generalize flow pattern data reliably. An objective approach based on vector addition is mathematically appropriate and effective in preserving the essential features of the sub-grid flow patterns. A quasi expert system approach developed by the automation of the WATFLOOD manual method of topographic parameterization is shown to be the superior approach to rescaling flow data for macro or regional scale hydrologic modeling. © 2008 Springer-Verlag Berlin Heidelberg.