Impacts of submerged breakwaters on nearshore sediment transport

Submerged breakwaters have been increasingly popular as the coastal defence structures due to the advantages of the low construction costs and less visual intrusion. However, the impacts of the structures on nearshore sediment transport and beach morphology remain unclear. This paper presents the results of beach morphological changes affected by different submergence of a group of shore-parallel breakwaters under the combined wave and tide conditions from a depth-average process-based coastal morphological model - COAST2D. In this study, different breakwater crest levels are used in the model under both storm waves and tides based on the field measurements at the Elmer breakwater scheme site to investigate the impacts of the breakwater submergence on nearshore hydrodynamics and morphological changes. The results show that the fully submerged breakwaters produce more stable and balanced sediment loss/gain in the protected area, and yield more desirable formation of salients behind the breakwaters. The results also reveal the complex nearshore processes and morphological changes under the extreme waves for further study