ANALYSIS AND COMPARISON AMONG CATCHMENT AREAS OF RAINFALL AND BASIN CHARACTERISTICS DOMINATING CONCENTRATION OF WATER LEVEL AND DISCHARGE PEAK TIME AT RIVER CONFLUENCE POINTS

- FOCUSING ON THE IRUMA RIVER BASIN OF ARAKAWA WATER SYSTEM -

Abstract

Climate change is expected to cause changes to the spatiotemporal characteristics of rainfall. This change may lead to increased flood discharge due to peak time concentration at river confluence points. The objective of this study was to clarify the spatiotemporal characteristics of rainfall which lead to the concentration of peak times of discharge at river confluence points for the Iruma River basin, Arakawa water system. Runoff characteristics were investigated in each catchment area based on past hydrological data, and the relationship with basin characteristics was clarified by multivariate analysis. By comparing them between each catchment areas, it is estimated that the peak time tends to be concentrated if the peak time of rainfall in Toki River basin is about 2 to 4 hours earlier than Iruma River basin.