2022 CSDMS meeting-031
Understanding shoreface equilibrium morphology: combining geologic and wave climate data with an energetics-based model
Megan Gillen, (she/her),MIT-WHOI Joint Program in Oceanography Cambridge & Woods Hole Massachusetts, United States. firstname.lastname@example.org
Andrew Ashton, Woods Hole Oceanographic Institution Woods Hole Massachusetts, United States. email@example.com
Jennifer Miselis, USGS Coastal and Marine Science Center St. Petersburg St. Petersburg Florida, United States.
Daniel Ciarletta, USGS Coastal and Marine Science Center St. Petersburg St. Petersburg Florida, United States.
Emily Wei, USGS Coastal and Marine Science Center St. Petersburg St. Petersburg Florida, United States.
Christopher Sherwood, USGS Coastal and Marine Science Center Woods Hole Woods Hole Massachusetts, United States.
The lower shoreface, a transitional subaqueous region extending from the seaward limit of the surf zone to beyond the closure depth, often serves as a sediment sink or source in sandy beach environments over annual to millennial time scales. Despite its important role in shoreline dynamics, however, the morphodynamics of the lower shoreface remain poorly understood. Previous work highlights discrepancies between equation-based theoretical equilibrium contours and bathymetric data, indicating that models may not accurately reproduce real shoreface cross-shore profiles. Here, we combine energetics-based suspended sediment transport formulae (Ortiz & Ashton 2016, JGR-ES) with wave climate and sedimentological data from Rockaway Peninsula, NY, to understand controls on shoreface morphology and differences between modeled and empirical equilibrium profiles. Analyzing a full wave climate time series from Wave Information Studies (WIS) spanning 40 years at one hour intervals reveals how different components of the wave climate affect suspended transport rates, particularly at varying depths. This results in a different steady-state, or equilibrium profile compared to one computed using single wave parameter inputs. The computed profile shape further changes when computations include reduction in sediment settling velocity due to offshore sediment fining, based on field observations. These profile are then compared to USGS bathymetric shoreface profile shapes at Rockaway and other locations. Our preliminary results appear to rectify the gap between modeled and empirical equilibrium profiles, moving towards a more thorough understanding the evolution of the lower shoreface.