Author(s): Hiroshi Yokoyama; Yasuhiro Yoshikawa; Hiroya Ogushi
Linked Author(s): Hiroshi Yokoyama
Keywords: River Ice; River Ice Breakup and Jamming
Abstract: Ice jam causes a sudden rise in water level and accidents involving the flowing river ice, which is one of the problems in the management of frozen rivers in Hokkaido, northern part of Japan. We have developed methods for predicting the location and occurrence time of ice jam to reduce the damage caused by ice jam for practical use in risk management of ice jam disaster. We organized the examination procedure considering a series of processes from the start of deicing of river ice to its occurrence, and the flow, destruction, and deposition, and examined its applicability in actual frozen rivers. We examined prediction process and results from the viewpoints of (1) appropriate pre-extraction of areas where ice jam will occur in each river channel, (2) appropriate pre-prediction of the start time of deicing, and (3) appropriate pre-prediction of the time when the risk of ice jam occurrence increases. The model is consisted of 3 steps. As 1st step, the points where possibility of ice jam occurence was higher in the longitudinal direction of the river channel could be extracted by generalized physical indicators, "ice jam scale". As 2nd step, by confirming the increase in water temperature and river depth as the river ice thickness changes, the time to start deicing could be estimated. As 3rd step, by predicting the rapid decrease in river ice thickness and increase in water depth due to the progress of snowmelt, it was possible to infer the rapid melting of river ice that causes ice jam.
Year: 2022