A dry dam becomes to be recognized as an effective river structure to control flood with reduction of sediment deposition in a reservoir as well as conservation of river environment. However, hydraulic characteristics and sediment transport behavior around a dry dam have not been clarified yet. This paper presents a one dimensional (1D) and a three dimensional (3D) numerical models, which can simulate flow structures and sediment transport for a dry dam. The computation with the present 1D model could predict reasonably the peak discharge cut effect during flood. It also could predict accurately the deposition patterns and sediment sorting upstream of the dam. On the other hand, the 3D model could simulate realistically a flow through a tunnel and a flow over the dam crest. The 3D model also implies the existence of three-dimensional recirculating flow inside the reservoir, which will affect the flow behavior and sediment transport near the tunnel during flood.
