Sediment Budget based on the mass of silt and clay on Intertidal Flat Adjacent to River Mouth

Abstract

To estimate monthly sediment budget based on a mass of silt and clay on an intertidal flat adjacent to Shirakawa River mouth, monthly bed level and net sediment flux monitoring were conducted from October 2006 to October 2007. The bed levels were measured using electric distance meter during low tides. Water level, flow current, and sediment concentration were measured continuously on the flat. The intertidal flat was accreted with normal discharge conditions mainly due to a net import along the coastal line directed to river mouth. However, the flat was eroded with large discharge conditions (1,500 m3/s) occurred during low tides. A net offshore sediment transport in the large discharge was four times larger than that in the normal discharge.