Abstract
In recent years, water related disaster risks have increased all over the world, therefore both non-structural and structural measures for flood management have been carried out. However, it is difficult to take thorough measures; therefore appropriate watershed management is being reconsidered. The unregulated peak discharge that used as important value for watershed management especially flood management is calculated using historical heavy rainfall data. Quantity of rainfall data is more plenty than river discharge data, however the hyetograph need to extend for making design flood discharge and hydrologic model has uncertainty issues. This paper proposes a new making method for flood exceeding the designed level using waveform of historical flood discharge data. The Jinzu River basin was selected for this study, which is basis of social and economic in Toyama prefecture. As a result of numerical simulation, high flood risk area was clarified in this basin. Finally, the existing design flood discharge 9700 m3/s was 1/150 return period; however the value was 1/500 return period estimated using the GEV distribution in this study. As the result of comparison between 10 probability distribution functions, the calculated probable discharges had large differences.
