Himalayan Geology, Vol. 39 (1), 2018, pp. 57-67, Printed in India
Quantitative analysis of Nayar River Basin, Garhwal outer Lesser Himalaya: Implication to neotectonic activity
A.K.L. ASTHANA1*, KHAYINGSHING LUIREI1, GIRISH CH. KOTHYARI2, POOJA PANDEY3
1Wadia Institute of Himalayan Geology, Dehradun 248001, India
2Institute of Seismological Research, Raisan, Gandhinagar 382009, India
3PEC University of Technology, Chandigarh, India
*Email (Corresponding author): aklasthana@wihg.res.in
Abstract: Tectonic is a major factor controlling the evolution of landscape in an active mountain like the Himalaya. Fluvial systems and landscape are greatly influenced by restive nature of the tectonic regime of the area. In this paper an attempt has been made to understand the tectonic activity in the Nayar Basin in the Garhwal Himalaya through field observations and computation of morphometric indices. The morphometric indices analyzed includes: the stream-gradient index (SL), Steepness Index (Ks), hypsometric integral (Hi), valley floor width–valley height ratio (Vf), and transverse topographic symmetry index (T). In Eastern Nayar River (ENR) the SL indices is characterized by high values with maximum reaching 1443 while in Western Nayar River (WNR) the maximum SL value is 770. The Steepness Index for ENR is 31295 while that of WNR is 8419. The concavity (θ) for ENR and WNR are 0.547 and 0.442, respectively, and the values suggests of recent tectonic activity in the Nayar Basin. Tectonic tilt of the NW segment of the study area as indicated by obtained T values suggest maximum stream migration towards NW. Vf and nature of the valley developed in Nayar Basin suggest youthful topography with narrow V-shaped valleys. The obtained values of stream length gradient index (SL), steepness index (Ks) and Concavity (θ) are indicative of recent tectonic activity. Structural control on drainage of the Nayar River is observed in the lower reaches where the river follows the trend of the fault. Structural controls of drainage pattern of smaller tributaries are also observed in the fault zones.
Key words: Garhwal Himalaya, Nayar River basin, morphometric parameters, tectonic activity, terraces.
