A study by scientists and students from the Wadia Institute of Himalayan Geology has revealed a 35,000-year history of river erosion in Ladakh Himalayas besides identifying hotspots of erosion and wide valleys that act as a buffer zone.
The study, published in the journal Global and Planetary Changes, showed how rivers in drier Ladakh Himalayas operated in longer time scales and how they responded to varying climate, an understanding of water and sediment routing, which is crucial as the country gears up its infrastructure and develops smart cities.
The research will help in understanding the river-borne erosion and sedimentation, which are the main drivers that make large riverine plains, terraces, and deltas that eventually become the cradle to evolving civilizations.
The scientists of WIHG, which comes under the Department of Science and Technology, traced where the rivers draining Himalaya and its foreland erode the most and identify the zones that receive these eroded sediments and fill up.
The Ladakh Himalaya forms a high-altitude desert between Greater Himalayan ranges and Karakoram ranges. The Indus and its tributaries are major rivers flowing through the terrain. The Zanskar River is one of the largest tributaries of the upper Indus catchment, draining orthogonally through highly deformed Zanskar ranges.
Two prominent tributaries of Zanskar River are Doda and TsrapLingti Chu, which confluence at Padam village in the upper valley to form the Zanskar River.
The Zanskar catchment was explored by the WIHG team to understand the landform evolution in the transitional climatic zone, using morpho stratigraphy and provenance study of landforms like valley fill terraces and alluvial fans (triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment such as silt).
Their research suggested that the wide valley of Padam, with an area of 48 square km, in the upper Zanskar has stored a vast amount of sediments in these landforms.
The study of sediments suggested that most sediments were derived from the higher Himalayan crystalline that lie in the headwater region of Zanskar.
It was found out that dominant factors responsible for sediment erosion were deglaciation and Indian summer-monsoon derived precipitation in the headwaters despite the presence of a geomorphic barrier (the deep, narrow gorge) between the upper and lower catchments of the river, and it remained connected throughout its aggradation history.