Wave transmission through the Eastern Scheldt barrier: a comparison of methods and data : memo

Hydraulic boundary conditions in the Eastern Scheldt at locations that are close to the Eastern Scheldt barrier are influenced by wave transmission through the barrier. Therefore the wave transmission through the barrier needs to be taken into account in the determination of hydraulic boundary conditions. Wave transmission is typically expressed in the form of wave transmission coefficients that indicate the fraction of the wave energy that passes the barrier. Alkyon (1998) first estimated frequency-dependent wave transmission coefficients based on two measurement locations, one seaward and one shoreward of the Eastern Scheldt barrier. Alkyon (2005) revised these estimates based on newly available measurement data from two additional measurement locations. In practice, predicted wave transmission appeared to overestimate the measured wave transmissions. lnaccuracies in the calibration of the SWAN models appeared to be an important factor in the overestimations (Gautier et al., 2014). Svasek (2014) repeated the study of Alkyon (2005) using calibrated models, which resulted in lower boundary conditions shoreward of the barrier. Recently, in context of the WBI project an alternative approach to estimate the wave transmission through the Eastern Scheldt barrier was formulated (Caires et al., 2016). The approach is based solely on the geometry of the barrier and is therefore not frequency dependent. The approach specifically aims at extreme conditions in which the water level can rise several meters. Therefore this approach is water level-dependent. This study compares the performance of the methods from Svasek (2014) and Caires et al. (2016) to account for the wave transmission through the Eastern Scheldt barrier with observations. Special attention is paid to the automation of the procedure as the procedure is to be (partially) implemented in a model train suitable for production computations for the derivation of hydraulic boundary conditions. For this purpose a Python package is developed.