Wave Overtopping of a Barrier Beach

The rate of wave overtopping of a barrier beach is measured and modeled as a first step in modeling the breaching of a beach impounding an ephemeral river. Unique rate of wave overtopping data are obtained from the measure of the Carmel River, California, lagoon filling during a time when the lagoon is closed-off and there is no river inflow. Volume changes are calculated from measured lagoon height changes owing to wave overtopping by a stage-volume curve, then center differenced and averaged to provide volume rates of change in the lagoon. Wave height and period are obtained from CDIP MOPS directional wave spectra data in 15m fronting the beach. Beach morphology was measured by GPS walking surveys and interpolated for beach slopes and berm heights. Three empirical overtopping models by van der Meer and Janssen (1995), Hedges and Reis (1998) and Pullen et al. (2007) with differing parameterizations on wave height, period and beach slope and calibrated using extensive laboratory data obtained over plane, impermeable beaches are compared with the data. In addition, the run-up model by Stockdon et al. (2006) based on field data is examined. Three wave overtopping storm events are considered when morphology data were available less than 2 weeks prior to the event. The models are tuned to fit the data using a reduction factor to account for beach permeability, berm characteristics, non-normal wave incidence and surface roughness influence. It is concluded that the Stockdon et al. (2006) model underestimates run-up as no overtopping is predicted with this model. The three empirical overtopping models behaved similarly well with regression coefficients ranging 0.72 to 0.86 using a reasonable range of reduction factors 0.66 - 0.81 with an average of 0.74.