Investigation of heavy shoaling process in small-or middle-scale harbors based on non-equilibrium suspended sediment transport analysis and field observation

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Through the field observation conducted at Iioka fishery Harbor in the periods from September 22 to October 14 in 1992 and from September 13 to October 25 in 1993, the mechanism of heavy shoaling of small-or middle-scale harbors has been investigated. The main findings in the field-data analysis are as follows.(1)Long-period motion in the water surface and horizontal velocity fluctuation was observed at the harbor entrance.(2)This long-period motion is generated by combined mechanism due to incident-wave groupiness and harbor amplification.(3)The long-period motion causes the flow separation at the harbor-entrance edges of the breakwater, which results in the generation of horizontal large-scale eddies. These eddies may suspend the appresiable amount of bottom sediment, which is then transported by the long-period motion towards the calm area in the harbor.