Influence of DEM resolution on drainage network extraction: A multifractal analysis

- Rényi spectrum is an efficient tool for determining the link between flow accumulation threshold value and DEM resolution.
- DEM resolution affects the selected flow accumulation threshold value and drainage network morphology.
- The flow accumulation threshold value increases as the DEM resolution increases.

Different hydrological algorithms have been developed to automatically extract drainage networks from digital elevation models (DEMs). D8 is the most widely used algorithm to delineate drainage networks and catchments from a DEM. This algorithm has certain advantages such as simplicity, the provision of a reasonable representation for convergent flow conditions and consistency among flow patterns, calculated contributing areas and the spatial representation of subcatchments. However, it has limitations in selecting suitable flow accumulation threshold values to determine the pixels that belong to drainage networks. Although the effects of DEM resolution on some terrain attributes, stream characterisation and watershed delineation have been studied, analyses of the influence of DEM resolution on flow accumulation threshold values have been limited. Recently, multifractal analyses have been successfully used to find appropriate flow accumulation threshold values. The application of this type of analysis to evaluate the relationship between DEM resolution and flow accumulation threshold value needs to be explored. Therefore, this study tested three DEM resolutions for four drainage basins with different levels of drainage network distribution by comparing the Rényi spectra of the drainage networks that were obtained with the D8 algorithm against those determined by photogrammetric restitution. According to the results, DEM resolution influences the selected flow accumulation threshold value and the simulated network morphology. The suitable flow accumulation threshold value increases as the DEM resolution increases and shows greater variability for basins with lower drainage densities. The links between DEM resolution and terrain attributes were also examined.