Namgang Dam is located in the upstream of Nam river. Namgang Dam controls flood for the
downstream of Namgang Dam using the Namgang spillway and the Sacheonman spillway with planned discharge.
However, it had not been evaluated adequately that the effect of the discharge through Sacheonman spillway on the
flood reduction of the downstream of Namgang Dam. This study performs runoff simulation considering the
discharge from Namgang Dam and Sacheonman spillway. And modeling results are evaluated for the flood reduction
effect of Sacheonman spillway on the downstream of Namgang Dam. This study uses a distributed model,
GRM(Grid based Rainfall-runoff Model) for runoff analysis. As a result, Sacheonman spillway is assigned more
discharge than Namgang Dam, and Sacheonman spillway greatly affects flood reduction in the downstream of
Namgang Dam.