Assessment of Digital Elevation Models Based on the Drainage Morphometric Parameters for the Tawi River Basin

Digital elevation models (DEMs) datasets are the fundamental input data for the conduction of the hydrologic, hydraulic, geomorphologic and ecohydrological modelling studies. Many practitioners from the hydrological, geomorphological and ecohydrological fields rely on open-access global digital elevation datasets due to their cost-effectiveness and sparse coverage of source at relatively high resolution. The recent literature replicates with a plethora of such studies that attempt to utilize various topographic datasets based on the various DEMs to study and access the physiographic characteristics as well as hydrological behaviour of the river basin. Now it is well-accepted fact that the basin's hydrological response (which is a reflection of the physiographic features of the basin) is closely related to fundamental geomorphic processes and landscape evaluations at local and regional scales. However, there is a fundamental question that arises about the accuracy and sensitivity of these topographic datasets based on the various available DEMs. Therefore, this study attempts to deals with five open-access DEMs viz., Shuttle Radar Topographic Mission (SRTM), ALOS Global Digital Surface Model “ALOS World 3D30m (AW3D30), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), CartoDEM and ALOS PALSAR-Radiometric Terrain Correction (ALOS PALSAR-RTC), etc. All the DEMs except ALOS PALSAR-RTC are with a spatial resolution of 30 m whereas ALOS-RTC DEM is with a 12.5 m spatial resolution. Estimation of about 25 morphometric aspects parameters that includes linear aspects, areal aspects and relief aspects are carried out for the Tawi river basin up to its confluence with the Chenab River basin. All these five types of DEMs are verified with google earth maps. Results show that ALOS World 3D30m (AW3D30) DEM data possess high accuracy in the delineation of the river basin as well as the presentation of the stream network followed by the CartoDEM, particularly in the low-lying area. However, the performance of ALOS-RTC DEM is the worst among all the studied DEMs. Further, an attempt has been made to subdivide the whole watershed area into fourteen sub-watersheds. The hypsometric integral analysis for these fourteen sub-watersheds has been carried out to compare different sub-watersheds irrespective of scale. Results of the hypsometric integral analysis using the AW3D30 DEM dataset indicate that the Upper Tawi sub-watershed had a high hypsometric integral value of 0.373 whereas the sub-watershed Sohagni had a low value of 0.147. The hypsometric integral value for the whole watershed was found to be 0.18. It was also found that the sub-watersheds namely Upper Tawi, Sardhan, Ramnagar, Balini and Lower Tawi were with high hypsometric integral values which indicate that these sub-watersheds are at a late mature stage of the geomorphological evaluation.