Spatial variability of topographic attributes and channel morphological characteristics in the Ladakh Trans-Himalayas and their tectonic and structural controls

Abstract

The Trans-Himalayas in India comprise of the Ladakh, Karakoram and Zanskar (also spelled as Zaskar) ranges. These ranges are marked out by the presence of several active major thrust faults, which are epicenters of recurrent seismic activity. Their alignments control the main stream courses of the area, resulting in sharp bends, obtuse junctions, steep defiles and abrupt changes in channel morphology, wherever streams transition across different morpho-structural units. The present study focuses on the drainage composition and topographic characteristics of the Leh and Nubra valleys in the Ladakh region, along the courses of the Indus, Zanskar, Shyok and Nubra rivers. The morphometric attributes and spatial variation in terrain aspects of the basins developed within the aforementioned three ranges and draining into these four rivers are examined using the ALOS PALSAR Digital Elevation Model (DEM) to elicit watershed and channel parameters related to tectonics. Thrust faults digitized from the available geological maps of the region are compared with the principal streams extracted from the above DEM dataset through an overlay analysis to discern the influence exerted by the principal thrust faults and other structural lineaments on the drainage alignment. Segment-wise stream gradient indices reveal the abrupt changes in longitudinal profile and resultant changes in channel morphological characteristics as the rivers traverse these various structural and lithological entities. These attributes of the drainage character are compared with the various lithological and geomorphic entities of the area, to elicit the river character in each physiographic unit.