VALIDATION OF AN OPEN-SOURCE AEOLIAN SEDIMENT TRANSPORT MODEL USING FIELD OBSERVATIONS FROM A BEACH-DUNE SYSTEM IN ARCATA, CALIFORNIA

The formation and evolution of beach-dune systems are governed by various biotic and abiotic processes including near-shore hydrodynamics, onshore aeolian sediment transport, and vegetation ecology. All of these processes are interdependent in coastal foredune systems and are influenced significantly by climate change impacts such as sea level rise and increasing the frequency and magnitude of storm events. To investigate beach-dune system responses to climate change, a recently developed, open-source aeolian sediment transport model (Aeolis) is validated with field observations from a restoration site at the Lanphere Dunes, Humboldt Bay National Wildlife Refuge, near Arcata, California. The model incorporates spatiotemporal variations in bed surface properties and other processes that limit or increase aeolian sediment availability such as sediment sorting, emergence of non-erodible surfaces, and hydraulic processes. Aeolis has shown reasonable capability of simulating coastal aeolian dynamics, but lacks capacity to incorporate spatial variations of wind velocity due to the interactions between beach and/or dune morphology and wind field. Accordingly, Aeolis has been recently extended to incorporate the spatial variations of wind field and the effects of dune vegetation on aeolian processes and sediment deposition. This update lacks extensive field validation, so this study uses field observations to investigate the performance of the model on simulating aeolian sediment transport on formation and evolution of coastal dunes in the study area. This site is experiencing the highest rate of sea level rise in California (+4.61 mm/yr) due to tectonic processes and this study is part of a larger investigation on assessing resilience of coastal foredune barriers to future sea level rise impacts. To validate the model, we use field observations including vegetation characteristics and elevation data obtained from cross-shore surveys along 52 km stretch of shoreline in the field site. We then, evaluate the erosional and depositional processes of beach-dune systems under future scenarios of sea level rise and increasing storminess. Our preliminary results suggest that Aeolis overestimated erosion rates across both beach and dune face, over a course of one year. This may be due to the lack of a multi-species vegetation core in Aeolis. Aeolis assumes single-species vegetation cover across the whole domain, whereas variable species with different growth and sediment trapping characteristics are present in the field.