Predictions in Ungauged Basins: Promise and Progress (Proceedings of symposium S7 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 303, 2006, 414-421.

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Disaggregation of upslope catchment area and steepest slope for transferring geomorphometric information across scales

NAWA R. PRADHAN¹ YASUTO TACHIKAWA² & KAORU TAKARA²

1 Graduate School of Civil Engineering, Kyoto University, Yoshida, Kyoto, 606-8501, Japan

pradhan@rdp.dpri.kyoto-u.ac.jp

2 Disaster Prevention Research Institute, Kyoto University, Uji, Kyoto, 611-0011, Japan

Abstract Higher resolution upslope catchment area values at finer grid sizes are lost, and slopes are underestimated, when DEMs with a coarse grid resolution are used. Thus dominating geomorphological parameters are directly influenced by the scale of DEM resolution. To overcome this problem, downscaling methods have been derived for both upslope catchment area and slope by introducing the concepts of number of sub-grids, influence factor and fractal method for scaled steepest slope. An application of the disaggregation method has been shown in the Kamishiiba catchment (210 km²) in Japan, with the successful derivation of the target fine resolutions for upslope catchment area and slope information from 1000 m DEM resolution.

Key words downscale; upslope catchment area, steepest slope, ungauged basin

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