Author(s): Wei Li; Peng Hu; Thomas Pähtz; Zhiguo He; Zhixian Cao
Keywords: Phase-resolving swash model; sediment transport; shallow water; swash zone
Abstract: Volumetric sediment concentrations computed by phase-resolving swash morphodynamic models are shown to exceed unity minus porosity (i.e. the maximal physically possible concentration value) by up to factor of 105 when using standard expressions to compute the sediment transport rate. An ad hoc limit of sediment concentration is introduced as a means to evaluate consequences of exceeding physically realistic concentration by standard expressions. We find that implementation of this ad hoc limit strongly changes the quantitative and qualitative predictions of phase-resolving swash morphodynamic models, suggesting that existing swash predictions are unreliable. This is because standard expressions inappropriately consider or ignore the fact that the shallow swash water depth limits the storage capacity of transported sediment.