Author(s): Yasuhiro Yoshikawa; Takaaki Abe
Linked Author(s):
Keywords: River Ice; River Ice Breakup and Jamming
Abstract: The tsunami triggered by the March 2011 Great East Japan Earthquake hit coastal areas and ran up rivers, generating large amounts of driftage. The damage caused by the waves was exacerbated by the fluid force of the tsunami itself and the collision force of the flotsam it created. Ice forms in rivers in cold snowy regions as the air temperature falls. In Hokkaido, rivers freeze for approximately 100 days from late December to early April every year. A tidal wave striking a frozen river will break and sweep away river ice, thereby increasing the amount of damage it causes. The March 2011 tsunami occurred during a river freezing period. In this study, a river ice variation model was created in consideration of river-ice breakup, movement and accumulation to examine the Mu River ice jam caused by the Great East Japan Earthquake tsunami. To verify the validity of the computation model used, hydraulic tests on ice jams were carried out and experimental/calculated values at certain water levels were compared. The model was also used for calculation to reproduce variations in the water level during ice jam conditions caused by the tsunami in the Mu River and to examine the ice jam phenomenon. In this study, a river ice variation model was set up, and experimental/observed values were compared to verify the validity of calculated values. The results highlighted the importance of specifying ice jam development conditions and the limit stress of ice plates for the model. Calculations were performed to reproduce changes in the water level when ice jams occurred in Hokkaido’s Mu River due to tsunami propagation, and the locations and behavior of ice jams were clarified.
Year: 2022