Indicators of Holocene high-stage flood events and tributary confluence migration in the lower Narmada Basin, western India

In this study, sedimentary deposits around the confluence of the Narmada River and its tributary, Orsang River, western India, were studied to understand the confluence dynamics. The results indicate that the sediment sequences exposed at three sites represent the contribution from the Narmada River, the Orsang River and the Heran River at various stages. During the Late Pleistocene, the sedimentation occurred as channel beds and bars in the wider than present and bedload dominant Narmada River. The channel aggradation, shifting and realignment, guided the Orsang River to change its course to flow through the lower course of the Heran River and join the Narmada in response to the early Holocene tectonic activity. High flood flows deposited fine sediments in the channel widening due to tributary confluence and within backflooded Orsang (tributary) valley during mid-late Holocene. The lateral migration of Narmada due to successive high flows during the mid-late Holocene probably led to the downstream movement of the Narmada–Orsang confluence.