Abstract

Mountainous rivers behave differently in transporting sediments. Unlike alluvial rivers in the plains, sediment concentration fluctuation in time and space is dominantly characterized by watershed behavior. Unstable slopes in the rugged and hilly topographical region, cultivation in steep terrain, thin vegetation cover, loose soils, soft fractured rocks, and intense precipitation are the main causes of sediment sources in rivers of Nepal.

Due to difficulties in operation, measurements of bed load transport are not done regularly in Nepal. The sedimentation studies where and whenever required, include indirect methods to assess total sediment transport. Therefore, a case study is carried out in Tadi river of Nepal. Bed load sediment sampling is done by Haley Smith type of sampler. Suspended sediments are sampled simultaneous by depth integrating method. Sediments passing though the gauging site are correlated with respective discharge and effective basin rainfalls. Regression analysis is also performed on bed load transport, suspended sediment, discharge and effective basin rainfall. The output ratings are applied for the estimation of annual sediment transport through the gauging section. Annual total sediment load through the same section is also assessed from other empirical formulae prevailing in Nepal. This paper summarizes basically the results and conclusions as an attempt in quantifying bed load transport in the river section under study.

Keywords: Tadi, Chameliya, Nepal, bed load, suspended load, transport, discharge, sediment rating