Abstract
In 1869 the Meiji Government launched the policy of encouraging migration to Hokkaido and started reclamation of the Ishikari River Basin. In September 1898, when farmland reclamation had started to expand, the Ishikari River was hit by an unprecedented heavy flood that resulting in catastrophic damage and 112 fatalities. This disaster prompted surveys for flood control. Okazaki et al. made detailed investigations and observations on the 1904 flood of the Ishikari River. Based on these investigations, a flood control plan focusing on cutoff works was formulated, and those works were implemented for the half-century from 1910. This study reviews the effects of the flood in 1904, which served as the basis for the flood control plan, on the primeval Ishikari River Basin of the time, utilizing the results of investigations by Okazaki et al. We use two-dimensional flood flow numerical simulation to examine the effects of cutoff works. We also explain how the flood control plan had the effect on the basin development.
