Author(s): Hiroki Yabe; Osamu Ohno; Hiroshi Yokoyama
Linked Author(s): Hiroshi Yokoyama
Keywords:
Abstract: Continuous flow discharge at the period of a frozen river is the important data for estimating water intake problems, water level rise and flooding caused by ice jams. The observation of water level and discharge is measured three times a month, and we estimate the continuous flow discharge using water level-discharge curve (H-Q equation) during periods other than the observational day. However the automatic water level observed during the freezing period is not accurate because it includes the thicknesses of river and crystal ice. These ice obstruct river flow, and change with time. Therefore, we have to substitute the water level considering these thicknesses into the H-Q equation in order to improve the accuracy of continuous flow estimation. Furthermore, since the river roughness coefficient during freezing period is different from it during the non-freezing period, it is necessary to apply the H-Q equation using the flow observation data during freezing. In this study we propose a continuous flow discharge estimation method that combines the estimated values of river and crystal ice thickness using the heat balance method, the H-Q equation considering these thickness during the freezing period, and the measured values. We obtained the hourly temperature, sunshine, wind speed, snowfall depth, and river water level data to apply the heat balance method at the target point. As a result of applying this model to the data for 12 years, it was divided into cases where the river ice thickness could be estimated approximately, the estimated values were oversized, underestimated, etc. When there is a difference between the estimated value and the measured value, the modified model with the measured value added as additional information was constructed and applied. As a result, the accuracy of river ice thickness estimation after the actual measurement date was improved.
Year: 2020