Sediment Transport and Morphological Response to Nearshore Nourishment Projects on Wave-Dominated Coasts

Abstract

Nearshore nourishments are constructed for shoreline protection from waves, to provide sediment nourishment to the beach profile, and to beneficially use dredged sediment from navigation channel maintenance. However, it is poorly understood how placement morphology and depth influence nearshore processes operated on wave-dominated coasts. This study investigates the wave fields, sediment transport, and morphological response to three common nearshore nourishment shapes, nearshore berm (elongated bar), undulated nearshore berm, and small discrete mounds, with numerical experiments utilizing the Coastal Modeling System. The nourishments are placed in depths between 3 m and 7 m with a volume of approximately 100,000 m3 and between 400 m and 1000 m in alongshore length. Numerical experiments are carried out in three distinct coastal settings with representative wave climates and geomorphology. Simulation results indicate that shallower, more continuous berms attenuate the most wave energy, while deeper, more diffuse placements retain more sediment. Results from this study improve the understanding of nearshore nourishment shapes and can support decision makers identifying the most appropriate construction technique for future nearshore nourishment projects.

Sediment Dynamics in Artificial Nourishments

“…Artificial nourishments are presently some of the most applied coastal erosion mitigation interventions [1]. Nearshore nourishments are constructed for shoreline protection from waves, to provide sediment nourishment to the beach profile, and to beneficially use sediment dredged from navigation channel maintenance [2]. According to Kroon et al [3], sandy nourishments can provide additional sediment to a coastal system to maintain its recreational or safety function under rising sea levels.…”

“…This Special Issue also contributes to numerical modelling research, which is also applied in cost-benefit assessments, ecological impacts, and laboratory works. It is poorly understood how the placed sediments' morphology and depth influence nearshore processes operating on wave-dominated coasts [2]. Ferreira et al [9] also state that it is essential to understand and adequately model the shoreline response after a nourishment operation in order to support the definition of the best intervention scenarios.…”

“…Numerical modelling can help in understanding processes and anticipating behaviours. Johnson et al [2] investigated the wave fields, sediment transport, and morphological responses to three common nearshore nourishment shapes, a nearshore berm (elongated bar), undulated nearshore berm, and small discrete mounds, using numerical experiments. The simulation results indicate that shallower, more continuous berms attenuate the most wave energy, while deeper, more diffuse placements retain more sediment.…”