Sediment transport at the river confluences: few observations from a sub-tropical plateau fringe river of eastern India

Abstract

ABSTRACT Confluences are often attributed by abrupt change in the load transport and encompass significant regional differences. Tributary watersheds of the Chotonagpur plateau fringe fans are widely reported to be the source of premier sediment yields causing amplification of sediment load in the trunk river. In this direction this article scrutinizes the role of tributaries on sediment transport at 11 confluence locations along 86.4 km stretched river Bakreshwar. The work revolves around two fundamental questions- How do tributaries contribute sediment load to the main river respective to their catchment size, length, runoff and sediment yield volume? and how do tributaries' interaction with the trunk stream influence the longitudinal continuum of sediment load in the receiving river? The study affirms that the junctions represent locations of abrupt change in the longitudinal gradient of sediment load. Size and length of the tributaries relative to the main stream have explicit controls on the post-confluence change in sediment load. Tributary watershed sediment yield is the foremost factor for amplifications of sediment load and morphological complexities at and downstream of the junctions. This work is a preliminary attempt and can hopefully stimulate ideas for fruitful and coherent scientific inquiry on river confluences particularly for Indian circumstances.