Fine sediment transport near coral reefs islands in the Singapore Strait

Abstract

The objective of this study is to determine large scale of fine sediment transport near coral reefs islands in the Singapore Strait. Coral reefs in the Singapore Strait face great pressure due to high sedimentation and turbidity, which cause decreasing of light penetration and of environment quality for the coral growth. Sedimentation and high level of turbidity are caused by large scale of dredging and land reclamations in the Singapore. The location of Singapore Strait between two major water systems, leads to complex tidal system of the strait. Tidal elevation is predominantly semidiurnal while current velocity is diurnal. Field data from several tidal stations and offshore observation points are utilized in order to analysis large scale of fine sediment transport. The representative of time series from each observation point during the southwest and northeast monsoon were selected based on the data availability and quality. Seasonal variation of current velocity shows eastward dominant flow during the SW monsoon and westward dominant flow during the NE monsoon. Residual flow plays more roles in the fine sediment transport than tidal asymmetry. Average residual flow ranges from 0.1 to 0.3 m/s with the peak 0.8 m/s in January. Wave action does not show significant impact to resuspension of fine sediment in deep water, but considerably cause fine sediment to resuspend at near surface. A turbidity level near coral reef islands corresponds to the fine sediment concentrations variation. High turbidity event occurs at all observation points and far from optimal level for coral growth. High turbidity event occurs more than weeks which is likely caused by resuspension of large sediment supply by strong currents.