A Study on the Causes of Sedimentation at the Quay Wall in Busan New Port

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Since the construction of the Busan New Port, dredging has been performed to deepen the navigation channel due to the continuous enlargement of vessels. However, since the recent confirmation of the phenomenon of sedimentation across the entire quay wall, it was initially assumed that the cause was simply the influence of suspended sediment flowing in from the Nakdong River Estuary. Therefore, a marine physical survey and numerical simulation of seawater flow and sediment movement were conducted centered on the Pier bridge to the Nakdong River Estuary, and a bathymetric survey was conducted within the Busan New Port and between the Pier bridge and Nullcha-do. As a result of the bathymetric survey, the net sedimentation within the port in a certain area of the port in 2017 and 2022 was 2,054 m<sup>3</sup>, and the amount of erosion in the fairway was no different from the amount of sedimentation in mooring basin. However, in the numerical simulation of sediment movement, erosion occurred in all areas except the Pier bridge, and the annual deposition was up to 5 times less than the actually measured topographic change, so it was determined that it is not a direct cause of the sedimentation across the entire quay wall of the New Port. In particular, the area that is eroded 1.5 m more than the planned depth of D.L.(-)17 m in the central part of the new port is widely distributed and the phenomenon of deposition on the quay wall shows that the initial assumption is not correct. Therefore, the scour for large vessels, the last factor that can affect the seabed of the new port, was additionally examined, and the seabed scour equation by the ship's wake speed was applied. As a result, it was confirmed that the maximum scour depth by the ship's wake speed is 1.5 m in the case of the largest vessel that can enter the port, 240,000 tons, and the scoured floating sand can move in the normal direction of the route.