Abstract
This study aims to clarify the mechanism of ice jams on ice-covered rivers. We focused on the phenomenon whereby river ice of various sizes accumulates in narrow spaces over rivers. Before conducting an ice jam hydraulic experiment, we developed a calculation model for the occurrence of ice jams formed from river ice of mixed sizes under one-dimensional unsteady flow. The occurrence of ice jam was found to depend on the ratio of river width to ice size. The calculation model created in this study was found to be able to reproduce the water level of the ice jam experiment.