A review and assessment of longshore sediment transport equations for coarse-grained beaches

Abstract

Previous assessments of analytical longshore sediment transport formulae have been heavily biased towards sand-sized sediment. All have noted the shortage of high quality field data from coarse-grained beaches against which to test predictions of longshore transport rates. In this paper, 12 existing formulae were identified as being potentially applicable for coarse-grained sediments and predictions from these formulae are compared using a measured annual transport rate from a shingle beach and a concurrent hindcast wave climate. Two new empirical equations are also derived, one from a numerical model calibrated against the same data set, the other derived from field experiments on coarse grained beaches. Energetics-based equations are found to give reasonable predictions of the shingle transport, despite being derived for sand beaches. In contrast, those dimensional analysis type equations which had been validated using laboratory data, grossly over-predicted the measured transport rates. The most accurate predictions were from formulae previously validated at sites similar to that used for this comparison and therefore require further testing against field data from dissimilar sites.