Abstract
This paper presents a set of numerical flow simulations to investigate the flood control ability of the Hyakken River channel which was constructed as a floodway of the Asahi River for preventing inundation of Okayama Castle in the 17th century when the modern hydraulics had not been developed. Calculation conditions like the channel topography and the design flood discharge were estimated by comparing the old description about the channel with the numerical data obtained in recent days. The computation by using unsteady shallow water equations showed the results which correspond to the records of flood events of the day, and the results also suggested that the channel was designed very reasonably even without the modern knowledge of hydraulics.
