Effect of Flood Peak Discharge Control by a Small Reservoir in an Urbanized Area—Case Study in the Kurabe River Basin, Japan

Recently severe damage of flooding by urbanizationwas frequently occurred. To prevent this damage, small reservoir wasconstructed in the urbanized residential area. This paper describes an effectof flood peak discharge control by a small reservoir (control reservoir) causedby rapidly developed urbanization. Although work for this purpose was conducted,research on the effects of the control reservoir was not conducted until now.This research, conducted by simulation, was a case study in the Kurabe RiverBasin in the Tedori River Alluvial Fan Area, Japan, based on the preciseinvestigation of the reservoir in the actual field. The study was conducted todetermine not only the actual control reservoir capacity for the newlydeveloped residential area but also the ideal capacity for all presentresidential areas and the largest capacity allowable for a maximum rainfallevent that recently occurred. The control reservoir effects between individualblocks and the entire basin area were compared by dividing the test basin into15 blocks (sub-basins). The results showed that the effects on the capacity perunit area of the residential area in blocks have close relationship with the decreasingratio of peak discharge in blocks. Consequently, the effects ofcontrol reservoir capacity and the limitation were clarified. In thefuture, control reservoirs should be constructed for all of the alreadydeveloped residential areas, for example, by utilizing underground car parking lot.The results of this research can contribute to the design of the controlreservoir for protection against flooding damage in urbanized areas.