Author(s): Yasuhiro Yoshikawa; Yasuharu Watanabe
Linked Author(s): Yasuharu Watanabe
Keywords: No keywords
Abstract: In Hokkaido, which is a cold and snowy region, ice forms on rivers mainly due to the temperature drop in winter. Yamashita et al. 1) produced an ice formation map of rivers in Hokkaido for the period between December 1986 and March 1987. Fukuda et al. 2) produced a distribution map of freezing index values (absolute values), which are found by accumulating only the negative values of daily mean temperatures, in Hokkaido for the period between November 1974 and March 1975. From these maps, it can be seen that that ice is likely to form on rivers in eastern and northern Hokkaido compared with other parts of the prefecture, and that ice is thicker in these regions because the freezing index values, which are correlated with ice thickness, are larger. Against such a background of ice formation in winter, rivers in eastern and northern Hokkaido are facing problems, including the elevation of water surface caused by ice jams and difficulties in water intake due to frazil formation. In this study, an attempt to clarify the difference in ice formation on different rivers and frazil behavior was made through periodic field observation, by establishing several observation points in the longitudinal direction along the rivers. Although detailed fixed-point observation has been made in past studies, there are few cases of consistent observation in upper and lower reaches as far as the authors know. The observation results of this study will thus contribute to future research and the examination of frozen rivers.
Year: 2008