Longshore transport at shingle beaches: An independent verification of the general model

The General Longshore Transport (GLT) model (Tomasicchio et al., 2013) and the Van Rijn (2014) expressionrepresent the only two available general formulae in literature for the estimation of longshore transport (LT)at sand, gravel and shingle beaches. The GLT model is based on an energy flux approach combined with an empiricalrelationship between thewave induced forcing and the number ofmoving elements. An independent verificationof the GLT model is performed for the estimation of the total (bulk) LT at shingle beaches.Without anyfurther calibration, the suitability of the GLTmodel, even for the shingles beach case, is assessed bymeans of thecomparison between the LT predictions and the observations fromtwo field data sets (Chadwick, 1989; NichollsandWright, 1991). In most cases the GLT predicts LT rates within a factor of 2 of the observed values. The predictivecapability of the GLT model is testedwith reference to two different formulae recently proposed in literature(Mil-Homens et al., 2013; Van Rijn, 2014). It is shown that the GLT model gives a better agreement with the observations(Chadwick, 1989;Nicholls and Wright, 1991; VanHijumand Pilarczyk, 1982) with respect to the otherconsidered formulae.Moreover, long term(annual) field data (VanWellen et al., 2000) have been used for a furtherverification. In addition, the GLT model confirms to have a better agreement even for the LT at dynamicallystable berm reshaping breakwaters (Lamberti and Tomasicchio, 1997; Van der Meer and Veldman, 1992).