2026 CSDMS meeting-020
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Modeling three-dimensional hollow infilling and failure recurrence in the Oregon Coast Range
Selina Davila Olivera,
University of Oregon Eugene Oregon, United States. sdavilao@uoregon.edu
Josh Roering, University of Oregon Eugene Oregon, United States. jroering@uoregon.edu
Ben Leshchinsky, Oregon State University Corvallis Oregon, United States. ben.leshchinsky@oregonstate.edu
Topographic convergent zones, or hollows, are depositional zones in steep, unchannelized valleys. Infilling and failure of hollows have been heavily studied with one-dimensional models (e.g., Dietrich et al 1986; D'Odorico & Fagherazzi, 2003; Davila Olivera et al., 2023), whereby hollows infill to a critical depth, at which failure initiates as a shallow landslide. However, advances in hillslope transport and landslide failure models present an opportunity to consider geometries and forces not accounted for in previous work. In a multi-dimensional framework, soils in hollows experience both basal and lateral forces that can affect the geometry of initiation zones and thus landslide volume. Here, we combine models for soil production and nonlinear transport to simulate soil depth through time for dozens of representative hollows with slopes varying from 28° to 45° in the Oregon Coast Range (OCR). As soil production and transport incrementally fill the hollows, the spatial distribution of soil depth is periodically extracted and assessed for slope failure using a three-dimensional slope stability model, MD-STAB (Milledge et al., 2014). The failure recurrence interval for each hollow is defined as the time step at which the factor of safety indicates failure. This process is repeated for a set of hollows with varying steepness, while varying cohesion and saturation, resulting in failure recurrence intervals ranging from 104 years for gentle hollows (~28°) to 102 years for steep hollows (~45°). By adapting CO2CHAIN (Lurin et al. 2023), we identified over 29,000 hollows across a 70km-wide area of the OCR. We observe that hollow failure recurrence substantially varies spatially with basin-averaged hollow slopes. Our maps of simulated recurrence time have the potential to inform stakeholders about landslide hazards and changes in failure occurrence as storm and wildfire intensity increases. Additionally, hollow failure timescales have implications for organic carbon budgets, nutrient exports throughout watersheds, and downstream habitats, particularly as anthropogenic consequences alter failure recurrence.
