Abstract
This paper presents a set of numerical flow simulations to investigate the flood control capacity of the Hyakken-gawa which was constructed as a floodway of the Asahi River for preventing inundation of Okayama Castle City in the 17th century. The river channel topography and hydraulic conditions for calculation were assumed almost same as the previous study, but the inundation to the eastside alluvial plain was calculated together to estimate its effect on the reduction of food damage in the castle city. The numerical simulation showed that the backwater caused by the transverse dikes in the floodway induced the inundation to the eastside plain just before the inundation would start in the castle city. The result suggests that the flood control planning in the age took the inundation to the eastside plain into account at the time of unusual flood events.
