宇治川流域の都市化と内水

Abstract

The Uji river basin, part of Ino Town adjoing Kochi City, is 13.9 km2 in area and is composedmainly of mountains. The narrow and lower plain of 2.2 km2 extending along the Uji river isused mostly as paddy fields and partly as urban areas. But the urbanization is recently advancingmainly along the Uji river in spite of the dangerous topographical condition from flood. Severalflood prevention works such as an increase of pump, the creation of a flood way of a tributary andthe improvement of river channel, have been hurriedly carried out after severe disasters in 1975 and1976.This paper examines the changes of flood risk due to the flood prevention works and the urba-nization in future on the basis of the results of flood analysis by the kinematic runoff and diffusivetank models. The results show that the effect of the flood prevention works is so great that theflood risk is reduced to one-tenth and/or one-fifth, and that the urbanization is undesirable becausethe flood risk is increased by a factor of two.