An evaluation of flood risk reduction utilizing green infrastructures in the greater Tokyo area

The purpose of this study is to evaluate the effects of runoff control by green infrastructures in densely urbanized residential areas in the Greater Tokyo Area (GTA) in order to reduce the risk of urban flooding. In this research, we make comparisons of the effects of runoff control between green infrastructure and the measures projected by the Tokyo metropolitan government, which are composed of a mixture of porous pavement, seepage pit, and trenches for infiltration. This paper reveals that a green infrastructure plan gives feasible measures considering land use conditions, but is inferior to that of a seepage pit and soakage trench plan in terms of the total essential site area and the required expense. However, theoretically, the expense of the green infrastructure is improved by creating incentives for residents.