Noboru Shinohara

Research about efficient dam operation during floods to achieve both flood control and water utilization

Tokuzo Hosoyamada

In recent years, heavy rainfall disasters have occurred due to the rapid development of rain clouds caused by typhoons and linear precipitation zones. The risk of river flooding due to large-scale flooding has been increasing. In the event of river flooding, dams are required to prevent the occurrence of flooding through flood control. In such cases, dams need to have enough free capacity to provide sufficient flood control to ensure the safety of rivers. However, as a practical matter, if the dam is expected to reach the surcharge level due to higher-than-expected dam inflow, the operation is shifted to emergency discharge operation to equalize the inflow and discharge. Emergency discharge may cause a rapid rise in the river depth and flood damage because the dam cannot control flooding. Therefore, it is necessary for dams to avoid emergency discharge and to operate dams so that the river depth does not reach the flooding hazard level.
In this research, an efficient dam discharge method was investigated to achieve both water utilization by securing water with dams and flood control by reducing the water flowing from the river basin in the event of flooding. Using this program, various discharge methods were set up, and dam water levels, discharge rates, and river depths were compared when the amount of water discharged from the dam was changed.
In the experiment, calculations were conducted using the following patterns: operations in which water was released at 90%, 70%, 50%, and 30% of the dam inflow; operations in which a lower limit was set on the amount of water released; and operations in which the amount of water released was inversely proportional to the inflow. As a result, the river water level rose sharply when the discharge was increased, and the river depth reached its maximum at the peak of the discharge regardless of the minimum discharge amount. Therefore, the present verification provides the knowledge that a constant discharge from the dam results in an efficient discharge that suppresses the increase in river depth, even when the total amount of water released is the same.