Importance of Antecedent Beach and Surf-Zone Morphology to Wave Runup Predictions

Purpose: The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to present results of initial research on an investigation into the forcing parameters of wave runup on an intermediate, barred beach using innovative observational techniques. A brief overview of the technology and processing used to extract wave data from the terrestrial laser scanner is presented, and relationships between runup, foreshore change, and wave characteristics at the base of the foreshore are investigated. In addition, discussion is provided concerning the implications and causes of foreshore morphology evolution and observed tidal oscillations in wave observations at the base of the foreshore. A new equation for runup is also presented. It is based on a mix of wave parameters measured at the base of the foreshore and from offshore. This new equation explains 73% of the variance in wave runup observations. The results of this work suggest that knowledge of both the surf-zone and beach morphology prior to an approaching storm is critical for accurate predictions of runup inundation and erosion.