A new remote predictor of wave reflection based on runup asymmetry

Reflected waves account for a significant part of the nearshore energy budget and influence incoming waves, nearshore circulation and sediment transport. The use of swash parameters to estimate wave reflection is investigated at three different beaches ranging from highly reflective to dissipative. It is observed that it is essential to account for swash processes when estimating reflection, in particular at intermediate and reflective beaches with a steep beachface. Our results show that runup asymmetry in uprush/backwash can be used as a proxy for dissipation in the swash zone: larger asymmetry values indicating greater dissipation. In our dataset, a reflection predictor based on runup asymmetry has better skill in comparison to empirical predictors based on surf similarity, because runup is a process that integrates both surf and swash zone wave transformation. Runup asymmetry behaves as a swash similarity parameter and reflects an equilibrium between swash period, slope and dissipation.