2022 Volume 78 Issue 6 Pages II_509-II_521
Concerned about the frequent occurrence of flood damage in recent years, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is shifting from the traditional flood control plan that focuses only on river channel improvement to the basin-scale flood control plan including the systematic response of many sectors to flood damage mitigation in the basin society. However, there are still many uncertainties in the specific content. In the Edo Period (the 17th to the mid-19th century), on the other hand, areabased flood control management was widely practiced, in which the flood flows in river channels and on floodplains were designed in closely related. Their ideas and works may serve as a reference for developing the basin-scale flood control plan that MLIT is considering. However, since most of the flood control projects at that time were only described in documents and simple drawings, the hydraulic effects of their practices were not very clear. Therefore, in this study, based on the results of numerical flow simulations with the topographic and hydrological conditions at that time, the “vivid hydraulic scenery”, which civil engineers at that time looked at on their working site, was reproduced, and the effects of their flood control planning and practices were discussed and assessed. Based on the above discussion results, the points to improve the current basin-scale flood control project were summarized; flood control facility design connecting the flows in river channels and on the floodplains; and respecting the nature of rivers which becomes wider with the increase of flood discharge.
