Author(s): Kenji Kawaike; Hajime Nakagawa; Nanae Watanabe
Linked Author(s): Kenji Kawaike, Hajime Nakagawa
Keywords: Flood disaster; Retarding basin; Numerical simulation; Ogura Pond; Overflow
Abstract: Recently, there have been several flood disasters in Japan caused by heavy rainfall. To mitigate the damage caused by such disasters, various structural and non-structural measures have been adopted. However, it is still difficult to reduce the damage. A huge scale of tentative water storage functions such as a retarding basin could be considered. We evaluated the mitigation effect of an assumed retarding basin against the actual flood event of 2013 in Kyoto, Japan, by conducting numerical simulations. During this flood event, the maximum water level exceeded the designed high water level at a few points. For the best combination of the length and height of the overflowing weir, and assuming a surrounding wall of this retarding basin, 37 million m3 of flood water was stored. Consequently, the peak flood water level was decreased by 0.8 m, and the water level did not exceed the designed high water level at any point. Thus, a retarding basin has mitigation effects on the exceedance flood hazards to some extent. Further, the total population of Japan is decreasing. If land use, particularly residential areas, can be efficiently regulated to the safer places, this type of retarding basin can be one of the most effective and feasible countermeasures.
Year: 2020