2022 CSDMS meeting-021


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Evolving hydrological landscapes: diverse morphologies and hydrological processes emerge from a coupled hydrogeomorphic model

David Litwin, (he/him),Johns Hopkins University Baltimore Maryland, United States. dlitwin3@jhu.edu
Greg Tucker, CIRES, Department of Geological Science, CU Boulder BOULDER Colorado, United States.
Katherine Barnhart, CIRES, Department of Geological Science, CU Boulder, now at U.S. Geological Survey, Landslide Hazards Program Golden Colorado, United States.
Ciaran Harman, Environmental Health and Engineering, Johns Hopkins University Baltimore Maryland, United States.

Features of landscape morphology including slope, curvature, and drainage dissection are important controls on runoff generation in upland landscapes, while over long timescales runoff plays an essential role in shaping these same features through surface erosion. Many hydrologists have speculated about the importance of this coevolution and its potential for generating hydrological insights; however, observational and computational limits have long prevented direct study of coupled hydro-geomorphic systems over long timescales. What kinds of hydrological features do landscapes exhibit when their runoff is `in-tune' with the form of the landscape? Here we answer this question using a new coupled hydro-geomorphic model that is sophisticated enough to capture saturated and unsaturated zone storage and water balance partitioning between surface flow, subsurface flow, and evapotranspiration, but efficient enough to drive a landscape evolution model over millions of years. We nondimensionalize the model to arrive at a minimal set of dimensionless numbers that provide insight into how hydrologic and geomorphic parameters together affect the ultimate state. Model results show a diverse array of behaviors observed in real watersheds, including the presence of variable source areas and nonperennial streams. We also found some results that were unique and surprising, such as non-dendritic drainage networks. We hope that these results will inspire hydrologists to consider the role that landscape history plays in the hydrological processes observed today and inspire geomorphologists to consider the role of more nuanced hydrological processes in long-term landscape evolution.