Recently, estuary choking occurs several times in Toufutsu river mouth every winter, and the dredging is carried out after occurrence of estuary choking. Estuary choking affect flood control, fisheries in lake, and so forth. In this study, we aimed to reveal the mechanism of estuary choking by observations, which are current observation, water level observation, sediment survey, and video monitoring at the entrance of the Toufutsu Lake. Followings were major accomplishments of this study.

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... n high tide level during the flood tide and incident wave from the right bank side occurred at the same time, estuary choking occurred in Toufutsu estuary. (2) In case that ground level of inland area is higher than the crown height of the revetment, estuary choking is likely to be caused by swash.