Abstract
Weekly to quarterly beach elevation surveys spanning 700-800 m
alongshore and 8 years at two beaches were each supplemented with
several months of ∼100 sub-weekly surveys. These beaches, which have
different sediment types (sand vs. sand-cobble mix), both widen in
summer in response to the seasonal wave climate, in agreement with a
generic equilibrium model. Results suggest differences in backshore
erodability contribute to differing beach responses in the stormiest (El
Niño) year. At both sites, the time dependence of the equilibrium
modeled shoreline resembles the first mode of an EOF decomposition of
the observations. With sufficient training, an equilibrium-informed
Extra Tree Regression model, that includes features motivated by
equilibrium modelling, can significantly outperform a generic
equilibrium model.