OBSERVATIONS OF SUSPENDED SEDIMENT PROPERTIES OFF THE TENRYU RIVER MOUTH, JAPAN

Study oil suspended sediment properties have reached a new phase by the application of laser transmissometry equipments that enable researcher to observe the sediment grain size fluctuation. However, there are still some disagreements on the factor affecting the suspended sediment grain size fluctuation. This study was aimed to investigate properties characteristics of suspended sediment off a river mouth, in terms of grain size, and percentage of organic matter in the deposited sediment. For this purpose, a series of field observations have been conducted at inner shelf of Tenryu river mouth of Japan. The observations were conducted mainly by deploying a set of equipments at a point located 1.4 kill from the coastline. The point has a depth of about 18.2 m from the mean sea level. Parameters measured were turbidity at two layers, i.e 60 cm above bed (cmab) and 230 cmab, horizontal and vertical currents profiles, wave heights and periods, salinity, suspended sediment particle size, and deposition rate. A Laser In-Situ Scattering and Transmissometry (LISST) 100 was employed to Measure the fluctuation of suspended sediment particle size within the measurements period. To measure the suspended sediment deposition rate, a time series sediment trap was installed to collect the deposited suspended sediment at 160 cmab. Results proved that the suspended sediment median grain size fluctuation was relatively affected by tides.