Sedimentation and the Role of Sediment Flush Discharge in the River Mouth of the Magome River Flowing through Coastal Sand Dune

This paper investigates the mechanisms of sediment movements under waves and currents in the river mouth of the Magome River. Special focus is paid on a function of “sediment-flush discharge” which was uniquely introduced to the Magome River to increase the river discharge and mitigate sedimentation problems around the river mouth. Analysis of various data showed that sudden and severe sedimentation is caused by overtopping of stormy waves while daily river discharge including sediment flush discharge flushes sediment in a more gradual manner. Numerical analysis was conducted to investigate quantitative effects of sediment flush discharge and showed that flexible control of sediment flush discharge adjusting to the sedimentation conditions should reduce the risk of inundation.