2026 CSDMS meeting-069
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Towards a mechanistic understanding of the evolution of wide bedrock valleys in landscape evolution models
Abigail Langston,
Kansas State University Manhattan Kansas, United States. alangston@ksu.edu
The lateral bedrock erosion component in Landlab is one of the few models of lateral bedrock incision and is essential for simulating the development of wide bedrock valleys and strath terraces in landscape evolution models. Although the lateral erosion component is an effective tool, it lacks some flexibility. The current lateral erosion component models both lateral and vertical erosion in a simple stream power model. I present here two newly developed versions of the lateral erosion component that allow for thresholds, pairing with any Landlab vertical incision component, and explicitly tracking sediment depth across the model domain. The primary motivation for including sediment cover is so that we can evaluate the relationship between lateral erosion rates vs. sediment cover on the bed and the mechanisms that underly the axiom that bedrock valleys widen when lateral erosion outpaces vertical incision due to sediment cover on the bed. The first modification of the lateral erosion component (LE_Mod1) tracks sediment depth across the model domain and is paired with SpaceLargeScaleEroder, which handles the vertical incision. LE_Mod1 handles lateral erosion of bedrock and sediment and maintains mass balance by sending eroded material to SpaceLargeScaleEroder in the following timestep. These modifications also allow an inlet for sediment in the model domain to change sediment flux from a point through time, which we used to simulate glacial/interglacial conditions. The second modification of the lateral erosion component (LE_Mod2) interfaces with the sediment flux dependent incision component, SedDepEroder. In LE_Mod2, the valley wall is undercut through lateral bedrock erosion and overlying material eventually collapses into the valley wall, as in the original component. But the modified component allows the user to explicitly set the grain size of the collapsed bedrock material. Transport capacity is calculated in LE_Mod2, and if possible, some or all of the collapsed wall material is transported away. These modifications allow the model to produce a range of behaviors between the two end members valley widening mechanisms presented in the original component and allow users explore how bedrock valleys widen in flashy vs. steady discharge environments.
