2024 CSDMS meeting-092


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Gully development and soil erosion in headwater catchments: An event-based approach using Landlab

Yuval Shmilovitz, The University of Colorado Boulder, CIRES Boulder Colorado, United States. yuval.shmilovitz@colorado.edu

Ephemeral, steep-side channels (known as gullies and arroyos) are fundamental elements of soil erosion that threaten agricultural lands worldwide with the associated expectation that landscape degradation will accelerate due to anthropogenic climate change. Gullies are also central to landscape evolution as they are dynamic features that intensively altered between infilling and incision phases in the recent geological past. Yet, exogenic (e.g., due to climate or land-use change) and autogenic (e.g., due to natural oscillations between erosion/deposition phases) drivers of gully formation and of changes in their widespread occurrence are incompletely understood and quantified. This is, in part, because erosional dynamics of gully landforms are complex and hard to capture due to: (1) episodic and discontinuous sediment movement in response to discrete rain events, (2) unstable channel walls with frequent mass wasting, and (3) soil and vegetation properties that vary dynamically thus altering both the hydrology and slope stability. In this work, we focus on developing a new catchment-scale gully erosion model that enables quantification of soil erosion rates and topographic evolution in response to changes in rainfall patterns and vegetation cover over historical and longer timescales. The model includes explicit representation of rainstorm runoff and erosion over sub-minute time scales. During simulation, soil particles are transported both in suspension and as bedload in accordance with their size. Episodic bank failures and headcuts evolve based on local stability criteria derived from soil properties and failure geometry. This poster presents the model configuration, its main components, and the general modeling approach that aims to bridging gaps between event-scale hydrology, sediment dynamics and longer-term landscape evolution models using new and existing components in the Landlab modeling library. We also present preliminary results of model validation against runoff and sediment data from a field site and a sensitivity analysis on how sediment flux and landform development respond to plausible changes in rainstorm properties, landcover, and vegetation dynamics.