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Dynamics of Sediment Transport and Erosion-Deposition Patterns in the Locality of a Detached Low-Crested Breakwater on a Cohesive Coast

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School of Civil and Architectural Engineering, Nanchang Institute of Technology, Nanchang 330099, China
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Department of Civil Engineering, Faculty of Engineering, Malaya University, Kuala Lumpur 50603, Malaysia
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School of Engineering, University of Warwick, Coventry CV4 7AL, UK
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Earth Observation Centre, Institute for Climate Change, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
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Smart and Sustainable Township Research Centre, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
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Authors to whom correspondence should be addressed.
Water 2019, 11(8), 1721; https://doi.org/10.3390/w11081721
Received: 8 June 2019 / Revised: 12 July 2019 / Accepted: 13 August 2019 / Published: 19 August 2019
(This article belongs to the Section Hydraulics)
Understanding the dynamics of sediment transport and erosion-deposition patterns in the locality of a coastal structure is vital to evaluating the performance of coastal structures and predicting the changes in coastal dynamics caused by a specific structure. The nearshore hydro-morphodynamic responses to coastal structures vary widely, as these responses are complex functions with numerous parameters, including structural design, sediment and wave dynamics, angle of approach, slope of the coast and the materials making up the beach and structures. This study investigated the sediment transport and erosion-deposition patterns in the locality of a detached low-crested breakwater protecting the cohesive shore of Carey Island, Malaysia. The data used for this study were collected from field measurements and secondary sources from 2014 to 2015. Sea-bed elevations were monitored every two months starting from December 2014 to October 2015, in order to quantify the sea-bed changes and investigate the erosion-deposition patterns of the cohesive sediment due to the existence of the breakwater. In addition, numerical modelling was also performed to understand the impacts of the breakwater on the nearshore hydrodynamics and investigate the dynamics of fine sediment transport around the breakwater structure. A coupled two-dimensional hydrodynamics-sediment transport model based on Reynolds averaged Navier-Stokes (RANS) equations and cell-centered finite volume method with flexible meshing approach was adopted for this study. Analysis of the results showed that the detached breakwater reduced both current speed and wave height behind the structure by an average of 0.12 m/s and 0.1 m, respectively. Also, the breakwater made it possible for trapped suspended sediment to settle in a sheltered area by approximately 8 cm in height near to the first main segment of the breakwater, from 1 year after its construction. The numerical results were in line with the field measurements, where sediment accumulations were concentrated in the landward area behind the breakwater. In particular, sediment accumulations were concentrated along the main segments of the breakwater structure during the Northeast (NE) season, while concentration near the first main segment of the breakwater were recorded during the Southwest (SW) season. The assessment illustrated that the depositional patterns were influenced strongly by the variations in seasonal hydrodynamic conditions, sediment type, sediment supply and the structural design. Detached breakwaters are rarely considered for cohesive shores; hence, this study provides new, significant benefits for engineers, scientists and coastal management authorities with regard to seasonal dynamic changes affected by a detached breakwater and its performance on a cohesive coast. View Full-Text
Keywords: coastal dynamics; coastal resilience; cohesive sediment; detached low-crested breakwater; erosion-deposition pattern; artifitial reef coastal dynamics; coastal resilience; cohesive sediment; detached low-crested breakwater; erosion-deposition pattern; artifitial reef
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Fitri, A.; Hashim, R.; Abolfathi, S.; Abdul Maulud, K.N. Dynamics of Sediment Transport and Erosion-Deposition Patterns in the Locality of a Detached Low-Crested Breakwater on a Cohesive Coast. Water 2019, 11, 1721.

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