Numerical modelling of sediment transport in artificial seamount by the action of tidal current

In order to study the influence of artificial reef on the sea bottom, based on the marine numerical model FVCOM (finite volume community ocean model) and its sediment transport module, the effects of the current field, suspended sediment and seabed sediment erosion and deposition around an artificial seamount in the artificial reef area of the Ma’an Islands are analyzed. A truncated-cone-type artificial seamount was set up with a diameter of 100 m and a height of 10 m. In order to simulate the effect of sediment suspension and seabed erosion and deposition around artificial seamount by the action of the tidal current, the part of the artificial seamount was simplified into a closed solid and the corresponding height of water depth was subtracted. Based on the analysis of the current field during the floods and ebbs of the spring and neap tides, the influence of artificial seamount on current velocity was mainly showed in the vicinity of the artificial seamount. The velocity of the water layer above the artificial seamount and velocity of bottom layer on both sides of the main current axis increased, while the velocity of downstream of the artificial seamount decreased significantly. The difference of suspended sediment concentration variation before and after the construction of artificial seamount was close to the trend of the current field variation and the maximum value was not more than 0.01 g/L. The results of sediment erosion and deposition on the sea bed around the artificial seamount showed deposition along the long axis of current ellipse, and erosion along the short axis of current ellipse, and the thickness of erosion and deposition were about ± 0.5 m, and the horizontal influence range was within 2.0 times of the diameter around the reef mountain, that is, within 200 m. The sediment transport process caused by the artificial seamount was a local change process. In order to avoid local over erosion, it is necessary to reinforce the seabed near the artificial seamount on the short axis of the tide ellipse with special bottom pretection reef. It is not suitable to build artificial seamount in the area where tidal current velocity is too high and bottom sediment is liable to serious erosion and deposition.