A SCALE INVARIANCE MODEL FOR SPATIAL DOWNSCALING OF TOPOGRAPHIC INDEX IN TOPMODEL

Abstract

Failure to translate scale dependencies of dominating geomorphometric parameters into effective hydrological models has posed a serious problem for ungauged basins where only coarse resolution elevation data is available. To overcome this problem, scale laws that govern the relation in digital elevation data resolution on geomorphometric parameters of topographic index of TOPMODEL have been analyzed. A scale invariance model for down scaling of topographic index distribution has been developed by introducing a resolution factor and a fractal method for the scaled steepest slope in topographic index. The method successfully derived topographic index distribution of fine resolution DEM by using only coarse resolution DEM. The scale invariance model has been applied to Kamishiiba catchment (210 km²) and it is shown that the down scaled topographic index distribution is similar to a target topographic index distribution.