Investigation of sediment convergence mechanism in the altered Nakdong estuary using the Regional Ocean Modeling System

초록

Nakdong estuary has been heavily altered by human activities such as damming to prevent the penetration of salt water, reclamation, and dredging. The reduction in tidal energy and river discharge due to the presence of the dam has caused a shift from a relatively tide-dominated estuary to a wave-dominated estuary. In this paper, we attempt to explain the mechanisms for the alteration of sediment transport and topography using the Regional Ocean Modeling System (ROMS). This model ran with wind, tide, river discharge, and waves as inputs and was verified with in-situ data of sediment transport measured at the river mouth of the Nakdong estuary in 2011. Then, the ROMS was utilized to investigate the convergence of sediment flux in the center of the estuary. The results show that when the river discharge was dominant during the summer, the flux gradient between the upper and lower estuary was responsible for the convergence of sediment in the middle of estuary. On the other hands, residual transport, under the combined effects of waves and currents at the river mouth, induced sediment flux into the estuary in absent of strong discharge.