STUDY ON SEDIMENT GRAIN-SIZE MEASUREMENT AND CALCULATIONS AT MULTIPLE POINTS ON THE SANDBAR IN CLASS B RIVER
Keywords:Babamegawa River, Sandbar, Particle size, Diameter50, Numerical calculation
In recent years, flood damage was frequently occurring by the flow rate of rivers has increased due to heavy rains such as typhoons in Japan. Therefore, understanding the particle size distribution of riverbed materials was an important factor in river planning and sediment outflow forecasting. However, in many cases, the grain size considered in numerical calculations was only for the surface layer because collecting heavy sediment labor, and it has not been studied much in the depth direction. In this study, sediment was collected from multiple locations on the sandbar in the middle reaches of the Babamegawa River, which was a Class B River in Akita Prefecture. Then, the particle size analysis was performed in the cross-sectional and longitudinal directions. Sediment was collected twice to see the change in grain size before and after the flood. From the results, the D50 of the sediment collected after the flood tended to be larger than that of the sediment collected before the flood in both the cross-sectional and longitudinal directions. In the depth direction, it was confirmed a layer in which the particle size changes and a layer in which the particle size does not change.