Mull, J. and Ruggiero, P., 2014. Estimating storm-induced dune erosion and overtopping along U.S. West Coast beaches.

Coastal foredunes protect lives, infrastructure, and ecosystems during severe storms. A range of approaches, ranging from simple (e.g., geometric) to complex (e.g., process based) predictive models, have been developed to quantify overtopping and foredune retreat during storms. At present, however, there is no widely accepted approach for assessing the vulnerability of coastal foredunes to erosion and overtopping hazards. Because different coastal regions have distinct storm and geomorphic characteristics, models need to be assessed and possibly adapted before they can be successfully applied to each unique region. In this study we apply a total water level (TWL) model and three simple foredune erosion models and assess their suitability for U.S. West Coast vulnerability analyses. The erosion models include a geometric model, an equilibrium profile model, and a wave impact model. We discuss the assumptions required to implement each model and force them with hydrodynamic conditions associated with a large-scale laboratory dune erosion experiment and a major winter storm approximately equivalent to the 30 year return period (TWL) event in the U.S. Pacific Northwest. The models are each applied with beach and foredune characteristics extracted from airborne topographic LiDAR (light detection and ranging) data collected along the coasts of Oregon and Washington. Sensitivity tests reveal distinct differences in model dependence on beach slope, a critical parameter in determining storm water level elevations and ultimately the extent of foredune retreat. Without detailed, reliable field observations of storm-induced dune erosion from the region, the accuracy of each model is determined using results of the dune erosion experiment. Estimates of both overtopping and erosion extent are normalized by foredune dimensions, enabling comparisons of relative vulnerability between different reaches of coast.