Abstract
Abstract. Climate and tectonics impact water and sediment fluxes to fluvial systems. These boundary conditions set river form and can be recorded by fluvial deposits. Reconstructions of boundary conditions from these deposits, however, is complicated by complex channel–network interactions and associated sediment storage and release through the fluvial system. To address this challenge, we used a physical experiment to study the interplay between a main channel and a tributary under different forcing conditions. In particular, we investigated the impact of a single tributary junction, where sediment supply from the tributary can produce an alluvial fan, on channel geometries and associated sediment-transfer dynamics. We found that the presence of an alluvial fan may either promote or prevent the movement of sediment within the fluvial system, creating different coupling conditions. By analyzing different environmental scenarios, our results reveal the contribution of both the main channel and the tributary to fluvial deposits upstream and downstream from the tributary junction. We summarize all findings in a new conceptual framework that illustrates the possible interactions between tributary alluvial fans and a main channel under different environmental conditions. This framework provides a better understanding of the composition and architecture of fluvial sedimentary deposits found at confluence zones, which can facilitate the reconstruction of the climatic or tectonic history of a basin.
Highlights
The geometry of channels and the downstream transport of sediment and water in rivers are determined by climatic and tectonic boundary conditions (Allen, 2008, and references therein)
Analogous to a base-level fall observed in nature, these changes caused an increase in main-channel slope near the outlet and the upstream migration of a diffuse knickzone that lowered the elevation of the main channel
We found that differing degrees of coupling may be responsible for substantial changes in the geometry of the main channel and the sediment transfer dynamics of the system
Summary
The geometry of channels and the downstream transport of sediment and water in rivers are determined by climatic and tectonic boundary conditions (Allen, 2008, and references therein). Tributaries are an important component of fluvial networks, but their contribution to the sediment supply of a river channel can vary substantially (Bull, 1964; Hooke, 1967; Lane, 1955; Leopold and Maddock, 1953; Mackin, 1948; Miller, 1958) Their impact on the receiving river (referred to as main channel hereafter) may not be captured by numerical models of alluvial channels, as most models either parameterize the impacts of tributaries into simple relationships between drainage-basin area and river discharge (Whipple and Tucker, 2002; Wickert and Schildgen, 2019) or treat the main channel as a single channel with no lateral input (e.g., Simpson and Castelltort, 2012).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
