Research on earth-and-sand control of the artificial reef installed near the mouth of a river

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Earth and sand are supplied from a river. The sands of the seashore are maintained when it moves to the shore by sea waves. It becomes a dynamic equilibrium. However, beach erosion progresses in the following case. It is reduction of a river discharge and sand. A lot of concrete blocks must be installed near shoreline, and the seashore must be protected. Moreover, when earth-and-sand supply is cut off, the depth of water of the front of wave absorbing works becomes deep. And it will be scattered about with subsidence one after another, and maintenance will take much cost.This research installs an artificial reef near a mouth of a river; the method of capturing the earth and sand from a river more effectively is the purpose. Installation of an artificial reef will produce a local seashore flow. A suitable setting position, method, etc. are examined using this. When installing an artificial reef near a mouth of a river, it is necessary to get to know about current appearance and earth-and-sand movement. In particular, it is necessary to clarify the sand trapping effect of the discharge earth and sand from a mouth of a river. It is observed that there is also an advance tendency of shoreline. Then, the geographical feature change characteristic of the artificial reef installed in certain seashore in the Sea of Japan was arranged.Moreover using the application of the extended type Boussinesq model, we calculate for the time series wave field around the opening. Furthermore, we compare the amount of geographical feature change using the various amount calculation formulas of sediment transport and the amount of local measured depth change. By installing an artificial reef group, it has ten percent of the amount of discharge earth and sand from a river.