Abstract
A simulation model was formulated to assess underground space inundation in the event of a large-scale flood due to a failure of a levee along the Ara River. Data on locations and structures of flood defense facilities such as frame barriers and flood gates at entrances and exits of subway stations or other underground spaces were included in the model. Conditions at connecting spaces at junction stations were also incorporated in the model. Both surface flow and tube flow simulations were integrated into the model. The results of the simulation indicated the following: 1) wide underground areas will be submerged by the tube flows spreading through connecting spaces at junction stations; 2) tube flows will reach central areas including Tokyo Station faster than surface flows: 3) if a levee failure occurs at Senju in Adachi-ward, a wide area including the central part of Tokyo will be inundated, although the surface flows will be limited to a smaller area; and 4) in some simulation cases, measures to block flood waters at openings such as entrances would effectively work to decrease the length of the submerged areas of tubes as well as to delay the spread of the inundation.
