Influence of DEM interpolation methods in Drainage Analysis

The accuracy of the Digital Elevation Models (DEMs) interpolated using four different methods was compared in two small watersheds in the Ecuadorian Andes. The interpolation methods compared were Inverse Distance Weighted, radial basis functions, ordinary Kriging, and TOPOGRID. A qualitative comparison was made between the stream network modeled in Arc Hydro and the digitized stream network. Modeled contour lines were also compared with the original dataset used in the interpolations. In addition, a quantitative comparison measurement was implemented using the Kappa coefficient of agreement. TOPOGRID outperformed the other models creating hydrologically correct DEMs, while Kriging and radial basis functions produced similar results of lower quality. Inverse Distance Weighted produced poor results especially in areas with gentle slopes. The quantitative comparison metric reflected the qualitative observations, and helped to evaluate the quality of a DEM when the difference in performance between two methods is not easily discernible.