This study applies a new method for better understanding the issues river problems. A case study is performed for one of the rivers in Bangladesh. It involved data collection by field survey and reviewing literatures. One of the most interesting findings of the study is to expand our knowledge for treating river problems associated to suspended sediment transport. The case study provided information showing the rational advantages of the new method and to explore the reasons of its pertinence.

This study proposes methods to create hazard maps for flood disasters with sediment and driftwood using a watershed model and a 2-D flood flow model, and applied the methods to the Akatani river flood disaster in 2017 to discuss their applicability and validity.

This paper proposes a method for describing large-wood behavior in terms of the convection equation and the storage equation, which are associated with active sediment erosion and deposition. Compared to the existing Lagrangian method, the proposed method can easily simulate the behavior of large wood in the flow field with active sediment transport. The method is applied to the flood disaster in the Akatani River in 2017, and the 2-D flood flow computations are successfully performed.