Model experiments of a river levee were conducted to examine the effect of the drain method by the soundness of its filter. The results of experiments show that the drain method makes a major improvement on the stability of the levee even when its filter is deteriorated. However, the effect of the drain method has been also affected by soundness of the filter. The clogging or damage to its filter causes the deformation of a levee toe. These results insist the possibility to monitor the soundness of the drain method by the deformation around the toe.
