At the Nenotani River in the Ota River basin, the maximum discharge was recorded during the heavy rainfall of H26.8, causing heavy damage. Although the channel had been improved after the flood, the revetment was damaged again during the heavy rain at 2018.7. In this study, two floods caused by the heavy rainfalls of 2014.8 and 2018.7 were analyzed for the river channel before and after the river improvement using Bottom Velocity Computation method. In addition, the effect of river improvement was evaluated quantitatively and qualitatively with water level and turbulence energy distribution. The methods showed the ability to examine the effect of river improvement quantitatively and qualitatively.
