Author(s): Ken-Ichi Hirayama
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Keywords: No Keywords
Abstract: Formation of ice cover in rather small and steep rivers, which are typical in Hokkaido, was studied. To have a close look at the ice growth in a river and changes in the flow, pictures were taken with the same camera angle once a day during two winters. Based on these pictures a rate of shore ice growth was expressed as a function of daily air temperature and a condition for the appearance of frazil ice in the river was derived. As the ice extends from the shore, changes of cross-sectional flow distribution and an increase of water stage were observed. It is also found from data in other rivers that an average ratio between Manning’s coefficient for ice-covered streams and for ice-free stream is about 0.8, and a frazil deposition under the cover is not possible when the flow velocity is more than 0.8 m/s or when Froude number is larger than 0.26. Then 2-D numerical model for predicting the growth of shore ice with a known air temperature and upstream water temperature was proposed. The results of the calculation were favourably compared with the observations.
Year: 1986