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The geomorphic and climatic settings strongly influence the hydrology and sedimenttransport characteristics of a large river system. The mode, efficiency, and scale of sedimenttransfer in a catchment are controlled by the degree of linkages between the differentlandscape components (i.e. sediment connectivity). Therefore, the spatial analysis andcross-correlation of hydrology, and sediment connectivity are essential in order to developeffective sediment management strategies and to mitigate the associated hazards inlarge-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.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 sedimentdischarge at Chatara is measured as 1546 m3/s and 101 million tonnes respectively before itdebouches into the plains of north Bihar, India. The rainfall in upper Kosi basin has largeregional and temporal variations due to considerable orographic contrast and the basinaverage rainfall at Chatara is 898 mm/yr. Observed discharge and sediment load data for ∼30years were analyzed and compared with the spatial sediment connectivity resultsderived from a topographic based index. This comparison helps to understand thespatio-temporal variability in sediment dynamics and its implications for floodhazard. The overall response of the Kosi basin towards sediment connectivity shows significantspatial contrasts among the sub-basins, and this is governed by several factors such aslanduse/landcover, slope and size of the basin. Our study reveals that out of ∼101 milliontonnes of annual sediment load at Chatara ∼40% is being transported from westerntributaries (Bhote, Indravati and Tama Kosi) and this confirms the that Bhote Kosi andTama Kosi are among the most dynamic and well-connected system. In contrast,the Tamor, a moderately connected system, contributes only ∼16% of the totalsediment load at Chatara. The remaining ∼44% is transported by other tributariesupstream of Chatara, the most important being the Arun (moderately connected),Dudh Kosi (highly connected) for which no independent estimates are available.Exceptionally high sediment flux is one of the most serious problems in the Kosi basin thatis linked to several river-related hazards and sediment connectivity analysis canbe extremely useful to understand sediment dynamics in such large river basins. [ABSTRACT FROM AUTHOR]