Assessing the Quality and Accuracy of Drainage Morphometric Analyses of Drainage Networks Extracted from Digital Elevation Models: A Case Study on Robate Gharebil Catchment in Northern Khorasan

This paper aims to assess the quality and accuracy ASTER DEMs and the ArcGIS alogorthms used for hydrologic analyses. To this end, first the plan of drainage networks in the region was extracted from aerial photographs and high resolution satellite images and was set as the real ground. In the next step, using the hydrology tool in ArcGIS software, raster networks of the region for the whole catchment area were determined in cell domains with 25 to 500 cells and then several geomorphologic units were extracted and the hydrographic features of the region were compared to the plans used as real ground. The results of the study show that the DEMs and the algorithms suffer from major imperfections. Although morphometric analysis of drainage networks are relatively compatible with the natural networks observed in raster format, there are still many large differences between the two; these differences were revealed using vector datasets for analyzing separate land features. The best threshold values for extraction of rivers from ASTER DEMs are 25 cells for head waters in the mountains, 50-100 cells for pediments, 100-250 cells in alluvial fans and 500 cells in plain domains.