Sediment dynamics and sediment connectivity in the upper Kosi basin, Central Himalaya: implications for river hazards

Earth Surface Science Institute seminar. Speaker Professor Rajiv Sinha, Indian Institute of Technology Kanpur.


The geomorphic and climatic settings strongly influence the hydrology and sediment transport characteristics of a large river system. The mode, efficiency, and scale of sediment transfer in a catchment are controlled by the degree of linkages between the different landscape components (i.e. sediment connectivity). Therefore, the spatial analysis and cross-correlation of hydrology, and sediment connectivity are essential in order to develop effective sediment management strategies and to mitigate the associated hazards in large-sized catchments (103-104 km2), where systematic field investigations are not feasible. The upper Kosi basin covers an area of 52, 731 km2 draining through Tibet and Nepal.

The rainfall in upper Kosi basin has large regional and temporal variations due to considerable orographic contrast and the basin average rainfall at Chatara is 898 mm/yr. Seven major tributaries namely, the Indrawati, Bhote Kosi, Tama Kosi, Dudh Kosi, Sun Kosi, Arun, and Tamor join at different points and the combined annual water and sediment discharge at Chatara is measured as 1546 m3/s and 101 million tonnes respectively before it debouches into the plains of north Bihar, India. Exceptionally high sediment flux is one of the most serious problems in the Kosi basin that is linked to several river-related hazards. Sediment connectivity analysis can be extremely useful to understand sediment dynamics in such large river basins.

This talk will present the analysis of historical discharge and sediment load data as well as spatial sediment connectivity results derived from a topographic based index and will discuss their implications for flood hazard.