2024 CSDMS meeting-098
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Evolution of Long-Profiles of a Sand-bed Alluvial River Network
Nilay Iscen,
University of Minnesota Minneapolis Minnesota, United States. iscen001@umn.edu
Fergus McNab, GFZ German Research Center for Geosciences Potsdam , Germany. fergus.mcnab@gfz-potsdam.de
Andrew Wickert, University of Minnesota Minneapolis Minnesota, United States. awickert@umn.edu
Alluvial rivers record the external drivers of change, such as climate, tectonics and anthropogenic disturbances, and they code their dynamics in their bankfull channel geometry and planform geometries and longitudinal profiles. The key to understanding the past and predicting the future alluvial rivers is learning to interpret the language of the grains of sediment and to decode the responses they record. Sand-bed river long-profile evolution model (SRLP) is a complete mechanistic model, describing both transient and steady-state long-profile evolution of a transport-limited sand-bed river by linking sediment transport and river morphodynamics, including planform (width) adjustment as a function of excess shear stress (following Parker, 1978, and Dunne et al., 2018), thereby linearizing the sediment-transport response to changing river discharge. Through quantifying the changes in the river's bed elevation, cross section, and channel slope, this one-dimensional, physics-based model captures the internal dynamics of this inherently complicated system and ultimately provides the critical information about how the river is responding to both natural and anthropogenic disturbances. We now further aim to understand and model how sediment is transported and where it is deposited within sand-bed alluvial river networks, how different portions of the alluvial river network respond and how the behavior of those network components are impacted over both human and geological time scales. In order to do this, we use an updated network model approach (by Wickert A., GRLP v2.0.0-alpha). This latest release works as a core network engine, allows integration of different process modules and ultimately provides a new network-model platform where we can include SRLP model. Through the addition of SRLP module, we present examples of long-profiles of sand-bed alluvial river networks under a variety of base level and water- and sediment-supply boundary conditions and investigate the mainstem river and both upstream and downstream tributary responses over time. Finally, we compare the response of the model of linked sand-bed tributaries to the one of gravel-bed rivers to further discuss the effects of variations in grain- and reach-scale dynamics on the longitudinal evolution of these two classes.
