Sensitivity of Quasi-Dynamic Topographic Wetness Index to Choice of DEM Resolution, Flow Routing Algorithm, and Soil Variability

Thao T. M. Nguyen and John P. Wilson
GIS Research Laboratory University of Southern California Los Angeles, California, USA
{thaotngu, Jpwilson}@usc.edu

Abstract:The steady-state topographic wetness index, which is frequently used to predict soil water content and sources areas for saturated overland flow, relies on two terrain attributes whose values have been shown to vary with both the grid resolution and flow routing algorithm that are used. A quasi- dynamic index (QD-TWI) has been proposed to help overcome the steady-state assumption that is implicit in the traditional form and not applicable in most semi-arid and arid landscapes. Few studies have examined the sensitivity of this index to variations in inputs and this paper examines its sensitivity to simulated DEM error, choice of DEM resolution and flow routing algorithm, and the variability of soil parameters for four small catchments in Dane County, Wisconsin.

Keywords: quasi-dynamic topographic wetness index; sensitivity analysis; error propagatio

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