Abstract
This study proposed a new methodology of largest scale hydrographs using the following three cases; 1) historical recorded daily rainfall of JMA, 2) Niigata-Fukushima heavy rainfall disaster in 2011, 3) ex-isting design rainfall. Those rainfall data were multiplied each catchment area of upstream.
Above mentioned three hydrograph as boundary condition, the Jinzu and Joganji Rivers were assumed to overflow at the same time, 2-D unsteady flow analysis was carried out. As a result of numerical simulations, Case 2 was calculated maximum flooding area, 15.3 % of city area. Moreover, maximum 13,944 people (4.3 % of city population) lost public shelters.