Levee Breach Experiment by Overflow at the Full Scale Experimental Channel

The increased occurrence of storm disasters caused by typhoons and local downpours in recent years has given rise to concerns over the possibility of large-scale floods resulting from river overflow. Levee breaches cause particularly severe damage, and in Japan, more than 80% of such accidents in the past have been attributed to overflow. Studies on levee breach by overflow have been conducted from various viewpoints using diverse methods. However, the mechanism of three-dimensional levee breach by overflow has not been clarified in past studies. Elucidation of this mechanism is very important for disaster prevention as well as for the future progress of studies on levee breach by overflow. Levees (levee crown width; 3m, levee height; 3m, levee length; 80m) were built in the Chiyoda Experimental Channel (full-scale experimental channel; width is 30m, length is 1,300m, maximum discharge is 170t/s) in Hokkaido Japan in 2010, and a three-dimensional experiment on levee breach by overflow. The findings of the experiment are as follows: After the beginning of overflow, levee breach widening did not begin until after most of the levee section had collapsed. It was also considered that, even if overflow occurred, extremely serious damage (e.g., sudden increase in levee breach width and overflow discharge) was unlikely unless the majority of the levee section collapsed.