巨椋低平流域の都市化と内水 (5)-出水規模を考慮した洪水対策試案-

Abstract

The Ogura basin situated in south of Kyoto consists of three drainage zones such as the Joudanzone composed of hill and high land of 27.4km2, the Chudan zone of middle land of 6.3km2, and theGedan zone of low land of 18.7km2 contained the reclaimed land of 10.8km2. The Ogura PumpStation with 13 pumps of 48.9m3/sec in total capacity is in active at the outlet of the basin.The basin is rapidly being urbanized mainly in the Joudan zone to exceed 50% in area in thenear future. To cope with flood changes due to the urbanization, the improvement of the RiverFuru being the drainage channel of the Joudan zone was began in 1971, and the Kumiyama PumpStation with a pump of 3Om3/sec was built at the end of the River Furu in 1973. These counter-measures, however, are not enough yet to deal with floods in the future.This paper discusses a desirable least counter-measure continuing the previous paper to mitigateflood disasters in the future, analyzing the flood behaviour by the kinematic runoff model and thedynamic tank model under a dangerous rainfall condition for every return period.As the results, the following two measures are proposed. (1) Increasing the pump capacity of60m3/sec to do 9Om3/sec in total at the Kumiyama Pump Station, and enlarging the side weir to 8times as large in length as the present to do 200m in total in the downstream of the River Furu to spillflood water temporary into the reclaimed land. (2) Increasing the pump capacity of 30m3/sec at theKumiyama Pump Station, enlarging the side weir to do 200m in length in the downstream of theRiver Furu, and setting a new multi-purpose retarding basin of 47.7ha in the middlestream of theRiver Furu. This retarding basin is divided into three lots to expect the effective land utilization.The lowest lot of 11.Oha is used for minor floods, the middle lot of 22.Oha for floods over 5 years returnperiod, and the highest lot of 14.7ha for severe floods over 30 years return period.