Evaluation of relief aspects morphometric parameters derived from different sources of DEMs and its effects over time of concentration of runoff (TC)

Abstract

An attempt has been made to study the relief aspects from three different sources of Digital Elevation Models (DEMs) viz., Survey of India (SOI) topographic map (1:25,000), Shuttle Radar Topography Mission (SRTM-90 m and SRTM-30 m) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER-30 m). These aspects are evaluated to examine differences among them and their influence on time of concentration (TC) of runoff at Moolbari Experimental Watershed (MEW), Sub Himalayan region (Shimla, District of Himachal Pradesh) India. For detailed study of relief aspects, morphometry parameters, SOI topographic map (as base map) were used. The results show that the relief aspects morphometric parameters derived from the SRTM30m and ASTER30m lie between SOI topographic map, and SRTM90m. We estimated TC of 21 micro watersheds from different sources DEMs by using Kirpich, Johnstone, Temez, and Barnsby equation only. Temez and Barnsby equation demonstrate high potential for the identification of TC from SOI Topographic map, SRTM90m, ASTER and SRTM30m DEMs. TC_Topo has a positive relationship with TC_SRTM90m, TC_ASTER and TC_SRTM30m for both Temez, and Barnsby equation with R2=0.804Topo & SRTM90m, 0.810Topo & ASTER & 0.839Topo & SRTM30m and 0.712Topo & SRTM90m, 0.747 Topo & ASTER & 0.785 Topo & SRTM30m. Further statistical test of Temez, and Barnsby equation based TC, only Temez equation based TC qualify/satisfy the statistical test. by considering all freeware DEMs a Semi-empirical model (SEM) has been developed, where TC predicted in term of TC_Topo is a function of TC_SRTM90m, TC_ASTER and TC_SRTM30m. This SEM has R2=0.883 and adjusted R= 0.874, Multiple R=0.907 and with Standard Error =2.131 at 95% confidence level. Comparison of the TC derived from the multiple regressions among three DEMs with TC_Topo shows an RMSE of 3.803, R-RMSE of 0.169, NRMSE of 0.342, R2 of 0.89, and RMSE% of 3.296 for Temez equation.