Author(s): Norio Tanaka; Yu Hasemi
Linked Author(s): Norio Tanaka
Keywords: Flood mitigation effect; Moat; Evacuation house; Fluid force reduction; Inundation depth
Abstract: In frequent flood affected areas like Yoshimi and Kawajima towns, a flood guard moat, Kamaebori (KA), around a protective mound, Mizuka, was developed in Japan about 300 to 400 years ago. A storehouse was then built on the mound and it served as an evacuation space in the event of a flood. There are several hypotheses to making a KA, i.e. dig the ground only for making a mound, or guard a house against floods. As the guard effects are still not made clear quantitatively and it provides a good information on strengthening the self-defense system, therefore, this study investigated how a KA and Mizuka mitigates flood by flume experiments. The KA was classified, through previous studies and field visits, into three types: a front type (FT), L-shape type (LT) and a horseshoe type (HT). The KA combined with a Mizuka, and woods (Yashikirin) surrounding the Mizuka, was mounted on to a flume bed. Flume experiments were then conducted initially without KA and then by each of the three types of KA each with a varying KA width. The experiment showed that FT with a large width of KA in the streamwise direction and HT irrespective of width size, decreased the water depth and fluid force on the storehouse that’s built on a Mizuka. The change of initiation of flood inundation water depth at the front side of Mizuka and the flood current repelling effect at unsteady condition were also investigated.
Year: 2018