2023 CSDMS meeting-109
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Long-Profile Evolution of Transport-Limited Sand-Bed Rivers
Nilay Iscen,
University of Minnesota - Twin Cities Minneapolis Minnesota, United States. iscen001@umn.edu
Andrew Wickert, University of Minnesota - Twin Cities Minneapolis Minnesota, United States. awickert@umn.edu
At the catchment scale, alluvial rivers co-adjust their planform, cross-sectional, and longitudinal geometries in response to changing water and sediment inputs, base level and the transport of this sediment through the fluvial system. In this study, we derive a simple, physics-based model to understand and predict sand-bed river long-profile form and evolution. This model links sediment transport and river morphodynamics, following an analogous approach to that taken by Wickert and Schildgen (2019) for gravel-bed rivers. It allows for planform (width) adjustments as a function of excess shear stress by following Parker (1978); this linearizes the sediment-transport response to changing river discharge, and ultimately suggests a diffusive form for sand-bed river long-profile evolution. Here, we also present model results of gravel- and sand-bed river long profiles under a variety of water- and sediment-supply and base-level conditions to discuss how these may help us to better interpret the geological and geomorphological context of alluvial rivers, and better predict their changes over time. This expression for the long-profile evolution of transport-limited sand-bed rivers provides forward momentum to merge theory and models for gravel-bed and sand-bed river systems, to look at the alluvial river system response as a whole (from bedrock-alluvial transition to the point at which backwater effects become significant) over both human and geological time scales, and to decipher the long-term rate and magnitude of this response to facilitate a better understanding of the evolution of fluvial landscapes.
