Abstract
This research undertook flood discharge analysis from urbanization using the unit flood discharge concept. The test site was selected at the Kurabe River basin, which is 17.5 km2 in area having a very steep landscape. Twenty-one rainfall events at 10-minute intervals were selected, and five urbanized years (1976, 1987, 1991, 1997 and 2009) were tested. It is estimated that the flood discharge increase to approximately twice during period from 1976 to 2009 (35 years), in which residential areas increased from 23% to 48%. Furthermore, we investigated the flood discharge changes due to urbanization from various aspects. For example, the flood discharge changes in the hydrograph, the effect of a small reservoir aiming to cut down the peak discharge, and the relationship between the unit discharge and, block and whole basin discharge, and the relationship between the discharges of our method and of estimated by a ‘Rational Formula’. Finally, the validity of our method was confirmed at the test site in the observed discharge.
