2026 CSDMS meeting-025
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Impacts of Erosional Style on Tectonically Varied Landscapes
Ann Thompson,
(she/her),University of Oregon Eugene Oregon, United States. annt@uoregon.edu
Kelin Whipple, Arizona State University Tempe Arizona, United States. kxw@asu.edu
Channel geometry provides insight into the patterns of rock uplift rate responsible for tectonically mountain fronts. However, such interpretations are often based on simplified models and can be improved by considering the role of sediment in river incision and landscape evolution. The erosion of many landscapes is influenced by both bedrock incision and sediment transport. In channels controlled by bedrock incision, uplift conditions can be decoded from channel steepness patterns. In contrast, sediment transport-controlled channels create broad, distributed patterns of channel steepness that are not easily interpreted. Mixed bedrock-alluvial channels, which have both mechanisms, can create a spectrum of responses between these two endmembers. Under these conditions, temporal changes in uplift rate may be misinterpreted as steady-state spatial uplift rate gradients. To explore this problem, we developed a Python Landlab component for the Shared Stream Power Model, a landscape evolution model that simultaneously models bedrock erosion, sediment transport, and sediment cover effects on river incision. We compare landscape responses to a steady-state, spatial gradient in uplift and a transient, temporal decrease in uplift. These conditions can be distinguished by the distribution of channel steepness: spatial gradients produce steepness transitions correlated with the mountain front, while temporal decreases produce transitions correlated with elevation. Increased sediment influence further modifies landscape response, producing smaller knickpoints, steeper trunk channels, and steepness gradients that vary with catchment size. From knickpoint size and spatial changes in channel steepness, we derive analytical solutions useful for determining Gh, a dimensionless number that quantifies the erosional style of a landscape, from topographic analyses. Together, these results provide a framework for distinguishing uplift conditions and constraining sediment effects in natural landscapes.
