Numerical modelling of intra-wave sediment transport on sandy beaches using a non-hydrostatic, wave-resolving model
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Numerical modelling of intra-wave sediment transport on sandy beaches using a non-hydrostatic, wave-resolving model Giulia Mancini1
· Riccardo Briganti1
· Robert McCall2
· Nicholas Dodd1
· Fangfang Zhu3
Received: 27 December 2019 / Accepted: 28 September 2020 © The Author(s) 2020
Abstract The mutual feedback between the swash zone and the surf zone is known to affect large-scale morphodynamic processes such as breaker bar migration on sandy beaches. To fully resolve this feedback in a process-based manner, the morphodynamics in the swash zone and due to swash-swash interactions must be explicitly solved, e.g., by means of a wave-resolving numerical model. Currently, few existing models are able to fully resolve the complex morphodynamics in the swash zone, and none is practically applicable for engineering purposes. This work aims at improving the numerical modelling of the intra-wave sediment transport on sandy beaches in an open-source wave-resolving hydro-morphodynamic framework (e.g., non-hydrostatic XBeach). A transport equation for the intra-wave suspended sediment concentration, including an erosion and a deposition rate, is newly implemented in the model. Two laboratory experiments involving isolated waves and wave trains are simulated to analyse the performance of the model. Numerical results show overall better performance in simulating single waves rather than wave trains. For the latter, the modelling of the morphodynamic response improves in the swash zone compared with the existing sediment transport modelling approach within non-hydrostatic XBeach, while the need of including additional physical processes to better capture sediment transport and bed evolution in the surf zone is highlighted in the paper. Keywords Wave-resolving modelling · Hydro-morphodynamics modelling · Intra-wave sediment transport · Suspended sediment concentration · Swash zone
1 Introduction Sandy beach evolution plays a key role in coastal vulnerability, influencing the stability of ecosystems and coastal communities’ economy and safety. Their morphodynamical evolution and response to drivers such as increased storminess remain difficult to predict (Wong et al. 2014). The exchange of sediments between the swash zone and the surf zone determines the evolution of the beach Responsible Editor: Bruno Castelle Giulia Mancini
[email protected] 1
Department of Civil Engineering, University of Nottingham, Nottingham NG7 2RD, UK
2
Deltares, Department of Applied Morphodynamics, 2629 HV, Delft, The Netherlands
3
Department of Civil Engineering, University of Nottingham, Taikang East Road, Ningbo, 315100, China
and shoreface (Masselink and Puleo 2006; Brocchini and Baldock 2008; Alsina et al. 2012; Masselink and Gehrels 2014). These two regions behave as interacting and coevolving morphodynamic subsystems. Consequently, it is difficult to separate the contributions of the surf zone and swash zone to the development and migration of breaker bars. Moreover, swash-swash interactions present in wave trains can a
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