Response of the River Jhelum to Active Tectonics, NW Himalaya

The River Jhelum and its tributaries form the main drainage system of the Kashmir Valley, India. Flowing through the axial part of the tectonically active Kashmir Valley, the river is characterized by diverse morphology manifested in channel width variations, meandering bends, braid bars, channel sharp bends, unpaired terraces, and perturbations in longitudinal profile. The river continuum extends from partly confined to laterally unconfined (alluvial) to confined variants. To ascertain the causes of this anomalous geomorphology, we divided the river into different reaches and used various techniques and river geomorphic indices to evaluate the river response to disturbing forces. Most of the geomorphic indices were calculated from Google Earth validated with field survey. The geomorphic indices used include sinuosity index (SI), lateral entrenchment ratio (ER), stream-gradient index (SL), and braided index (Bi), augmented with river width and longitudinal profile analysis. In the middle reaches, the river is more sinuous than the upper and lower reaches owing to the presence of less cohesive material and the gentle gradient. River terraces are mostly observed on the left bank, while the right bank terraces show occasional presence due to continuous lateral erosion reflecting ongoing valley floor deformation associated with Himalayan tectonics. An abundant sediment supply from the high gradient tributaries, variation in water discharge, channel planform geometry, and width characteristics have resulted in the braided character of the river in some of the reaches. Our results of geomorphic indices and field observations reveal that the channel morphology is controlled by both tectono-geomorphic processes and anthropogenic pressures.