In order to evaluate sediment transport processes for sustainable river sediment management, we conducted basin-scale numerical simulations in the Sangu River. The simulation results show that a considerable amount of sediment is transported from the upstream and subsequently deposited in the downstream and middle stream reaches. The analyses also find that the implementation of check dams in the upstream area significantly reduces sediment deposition in the downstream area.

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.