2020 年 8 巻 1 号 p. 71-78
In recent years, levee breaches have occurred occasionally, requiring the development of technology to mitigate the damage caused by such breaches. Therefore, it is vital to clarify the levee breach phenomenon. Levee breach experiments have been performed using the Chiyoda Experimental Channel to obtain various data. However, those experiments were performed under limited river channel conditions. Using the numerical-computation model developed on the basis of the experiments performed so far, the effects of river width and riverbed slope on the levee breach phenomenon have been studied. A steep-slope riverbed develops, not depending upon the river width, but on the levee breach expansion in the longitudinal direction, whereas a gentle riverbed develops remarkable depressions, and wider river width causes flooding close to direct overflow. The characteristics of the river channel were classified into four categories to determine the different types of levee breaches and to show how to approach effective methods to reduce the risk of a disaster.