The consideration of slump blocks in the coupling fluvial erosion and cantilever failure model is the recent advancement toward dealing the phenomena of riverbank failures. In this study, we developed a numerical modeling of a cantilever failure that uses a triple-grid approach to simulate the behavior of a cantilever within the framework of fluvial erosion, the cantilever's subsequent failure, slump block effect and bedload sedimentation. Two cases of cohesive materials with the different percentages of silt-clay content were simulated under the similar hydraulic conditions with and without slump block consideration. The simulated results in terms of the fluvial erosion and cantilever failure showed significantly difference due to inclusion of slump block consideration. The present numerical model with slump block consideration satisfactorily reproduced the riverbank failure phenomena and showed good agreement with the experimental results in terms of the spatial-averaged bank width along the riverbanks.