2020 CSDMS meeting-085

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Incision across a lithologic boundary: A Landlab-built model with applications to High Plains evolution

Vanessa Gabel, University of Colorado Boulder Colorado, United States. Vanessa.gabel@colorado.edu
Greg Tucker, University of Colorado Boulder Colorado, United States.

Fluvial incision since late Miocene time has shaped the modern transition between the Central Rocky Mountains and the adjacent High Plains of North America. Incision has formed a distinctive pattern of deep gouges at the mountain front centered around large drainages, most notably the Arkansas and South Platte Rivers. While there is a clear contrast in material strength and erodibility between the crystalline rocks that comprise the core of the mountains and the sedimentary packages that overlie the plains, researchers seldom account for this contrast when attempting to model the geomorphic evolution of the plains. In this study we set an explicit boundary across which erodibility changes from a value representative of granite, for the Central Rockies, to a value representative of coarse sandstone, for the High Plains. We then evolve the landscape with constant, uniform uplift and fluvial incision with sediment transport dependent upon a characteristic transport length. We find that with no external forcing beyond steady uplift and even on a landscape of modest gradient, it is possible to recreate deep incision at the mountain front simply by running water across substrates with highly contrasting erodibilities. This preliminary result has applications to future studies of the geomorphic evolution of the High Plains as it causes us to re-evaluate the sensitivity of this landscape to the material properties of the mountains and plains. In future work, this may guide us to look more closely at intrinsic properties of the landscape as an explanation for geomorphic expression before considering external forces.