• Flood propagation;
  • speed;
  • valley;
  • water level hydrograph


Understanding the effects of the planar, longitudinal, and cross-sectional form (channel shape) of a river channel on the propagation of a flood flow is important for proper river improvement and management. This paper shows that the propagation characteristics of a discharge hydrograph of a flood flow are closely related to temporal changes in the mean velocity. We defined the storage volume of a flood flow produced by a decrease in the mean velocity as the ‘retarding storage volume of a flood flow’. By using observed data and unsteady two-dimensional flow analysis of a flood of the Go River valley in June 1999, the propagation mechanics of the discharge hydrograph is described in relation to the channel shape, storage volume, and retarding storage volume.