Study on the effects of artificial excavation pits on the hydrodynamic characteristics of regular wave over fringing reef
Based on the nonhydrostatic single-phase flow numerical wave model(NHWAVE),this paper systematically analyses the effects of artificial extraction pits on the hydrodynamic characteristics of regular wave fringing reefs.The results show that the artificial excavation pits increase and decrease the local wave height in front of and inside the pits respectively,but the pits have no significant effect on the change of local wave height near the reef edge and the shoreline behind the reef.excavation pits had little effect on the change in mean water level.As the incident wave height increases,the magnitude of the change in local wave height near the excavation pit decreases relatively,but the wave setup increases with it.The greater the water depth on reef flat,the greater the amplitude of change in local wave height near the excavation pit,but the effect of wave setup on the reef decreases as the water depth on reef flat increases.As the wave period increases,the phenomenon of wave height increasing in front of the pit and decreasing in the pit is more pronounced;this phenomenon hardly occurs for small wave periods.The location,width and depth of the artificial excavation pits have a significant effect on the evolution of the propagation deformation of regular waves;as the pits move from the reef edge to near the shoreline,the phenomenon of wave height increasing in front of the pits and decreasing inside the pits gradually becomes less pronounced,but the mean water level near the shoreline gradually increases;as the width and depth of the pits increase,the mean water level near the shoreline gradually decreases.The presence of excavation pits increases the wave reflection coefficient to some extent;the presence of excavation pits significantly reduces the wave runup near the shoreline.The results of the study may provide a further reference for assessing sand mining activities on coral reefs.
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