Author(s): Ken-Ichi Hirayama
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Abstract: Field measurements for ice-covered streams were planned and performed in Hokkaido to improve our knowledge concerning winter regime of rivers and to get better standards for winter water discharge measurements. From the measurements, these were clarified that a vertical movement of ice cover and a change of water level had a one-to-one correspondence and that longitudinal slopes of water surface, in many reaches of a river, were steady during a period of complete ice cover though it was considerably raised by an existence of the cover. Velocity distributions under an ice cover were also measured by a Pitot tube with a heater and the accuracy of the two-point method was found to be less than +5%. Based on these findings, a method was proposed to predict an amount of increase in water stage caused by an ice cover. Though the use of this method is restricted to cases when there is no frazil ice accumulation under the cover, the adaptability of the method proved to be satisfactory. A parameter K in applying the method, which depends on the gradient of the water surface as well as the roughness of both ice and river bed, can be determined empirically without difficulties.
Year: 1978