2026 CSDMS meeting-085
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Rethinking the CERC Formula: Observations from XBeach Wave Field Modeling on Simple Shoreface Assemblages
Aidan Dealy,
(He/Him),Duke University Durham North Carolina, United States. aidan.dealy@duke.edu
Alongshore sediment transport is fundamental to the evolution of sediment-mantled coastlines and therefore is an integral part of forecasting long term shoreline change. Alongshore transport is currently understood to be a function of wave conditions, and the CERC formula has been the most utilized representation of this function. However, this formula relies on an empirical coefficient that varies significantly due to local beach characteristics. It also does not take into account the bathymetry of the shoreface, which is a key factor of sediment transport in coastal environments. This study proposes a methodology to use the modeling software XBeach to compute a more generalizable formula for alongshore transport. We first build our parameter space by varying characteristics of simple shoreface assemblages: the slope of the fair-weather shoreface, the slope of the fair-weather surf zone, and the width of the surf zone. Employing the methodology from Ricondo et al., 2024, we use the following four variables to model the initial wave train parameter space: significant wave height, wave steepness, wave angle, and offshore water level. These parameters are then put into a hydrodynamic model to compute our breaking wave parameter space. To keep computational costs realistic, we must choose a subsample of our initial wave train parameter space to model. We first employ latin hypercube sampling to generate a discreet parameter space. Following Camus et al., 2011, we then use a maximum dissimilarity algorithm to choose our subsampled parameter space. By inputting our generated bathymetry and wave conditions into the 2D XBeach non-hydrostatic model, our outputted breaking wave parameters are as follows: the root-mean-square wave height, the wave setup, the alongshore component of the Eulerian current velocity, and the mean wave angle. We also output the net alongshore sediment transport. We then reconstruct an interpolated continuous manifold of both the breaking wave and sediment transport parameters using principal component analysis and radial basis functions. Including the bathymetry components, we invoke a functional space R^3 by R^4 to R, where the bathymetry manifold is embedded in R^3, the breaking wave manifold is embedded in R^4, and alongshore sediment transport is embedded in R. We will then use the data distribution in this functional space to synthesize an analytical relationship between alongshore sediment transport, bathymetry, and breaking wave characteristics.
