超音波測定機器を用いた河川結氷時の河氷底面形状の現地調査

抄録

We observed the shape profile of river ice underside using acoustic rotary sonar. Firstly, we drilled small holes on the river ice, and put the rotary sonar into the water. Next, we measured the length of 16 directions from the rotary sonar to river ice. Then, we calculated 0.06×0.06(m)-mesh data from the observed data and transferred to the shape profile of river ice underside. We carried out another observation that is the time series vertical distribution of velocity using ADCP fixed at the river bed, and calculated roughness factor of river ice. Ice thickness estimated by roughness factor tended to decrease with time, it corresponded with the ice thickness observed by rotary sonar. To consider accuracy of our measurement, the observed shape profile of river ice underside compare with the calculated profile by ice thickness formula considering heat balance. The result shows good agreement with each other. It is clear that the shape profile of river ice underside was influenced by air temperature, water temperature, flow velocity and the depth from river ice to river bed.