ROLE OF RIVER DISCHARGE, SEDIMENT LOAD AND RELATED EROSION IN LANDSCAPING OF WESTERN HIMALAYA

The Himalayan landscape is controlled by exhumation, uplift and related erosion rates due to tectonic movements as depicted by channel flow, accretionary wedge or out-of-sequence thrusting models. The southern Himalayan front controlled by the elevated profiles formed due to raising and uplift acts as orographic barrier to heavy rainfall due to Southwest monsoons depicting higher river discharge rates, sediment load in large transverse rivers such as Sutlej, Alaknanda and Bhagirathi rivers in the western himalayas during monsoon periods and culminating into mega-disasters e.g. cloud bursts, flash floods, landslides etc. The rain shadow facing northern slopes of Himalaya and Tibet where westerlies dominate is affected by high river discharge and sediment load due to consquent glacial melting especially as observed in1998, 2005 and 2010 being the warmest periods in last 50 years. It is also affected by increase in temperature anomolies since 1951 after the industrial development as observed by GISS temperature anomolies in the northern himalaya and Tibet. GRACE data observed in these areas depict increase in glacial melts since 2000 and peak melting in 2005,2010 and 2013 showing higher discharge and sediment load in Sutlej, Bhagirathi and Alaknanda rivers in Western Himalayas culminating into snow avalanches and GLOF. The heavy silt load and higher river discharge incise rivers at much faster rates due to glacial melting in winters/ early summers and orographic rainfall during monsoons. This interpretation will be presented based on collection and analysis of data of river discharge, sediment load, erosion rates at different locations at Spiti,Sutlej, Bhagirathi and Alaknanda rivers (1974-2011) alongwith rainfall from actual locations/TRMM and GRACE data.