Abstract
River flood and inundation model has been constructed and a flood in the Arakawa River (AR) was simulated for clarifying sensible flooding risk in the middle basin of the AR, and the mitigation effects by existing secondary embankments constructed in Edo Era. 1947-flood type which recurrency is 200 years was used in the simulation and the difference of inundation situation was analyzed under the condition at which secondary embankments exists or not. Inundation starts from Wadayoshino River and Ichino River both of which Saitama Pref. manages. In the main AR, flooding starts from the upstream of the right hand side of embankment at Yoshimi Town, where is just upstream of narrow river width. The flooding situation is similar to 1910 flood. Although the embankments height and course was changed, sensible risk is located in the similar area. Aiage Bank and Nagaraku Bank can store the inundation flow and delay the flooding in the downstream region around 7.8 and 2.5 hours, respectively. Yokote Bank alo has the ability to delay the flood current around 1.8 hours.
