During the first week of July 2018, widespread flooding caused extensive damage across several river basins in western Japan. Among the affected basins were the Mabicho district of Kurashiki city in the lower part of the Oda river basin of the Okayama prefecture. An analysis of such a historical flood event can provide useful input for proper water resources management. Therefore, to improve our understanding of the flood inundation profile over the Oda river basin during the period of intense rainfall from 5–8 July 2018, the Rainfall-Runoff-Inundation (RRI) model was used, with radar rainfall data from the Japan Meteorological Agency (JMA) as the input. River geometries—width, depth, and embankments—of the Oda river were generated and applied in the simulation. Our results show that the Mabicho district flooding was due to a backwater effect and bursting embankments along the Oda River. The model setup was then redesigned, taking into account these factors. The simulated maximum flood-affected areas were then compared with data from the Japanese Geospatial Information Authority (GSI), which showed that the maximum flood inundation areas estimated by the RRI model and the GSI flood-affected area matched closely. River geometries were extracted from a high-resolution digital elevation model (DEM), combined with coarser resolution DEM data (global data), and then utilized to perform a hydrological simulation of the Oda river basin under the scenarios of backwater effect and embankment failure. While this approach produced a successful outcome in this study, this is a case study for a single river basin in Japan. However, the fact that these results yielded valid information on the extent of flood inundation over the flood-affected area suggests that such an approach could be applicable to any river basin.

中文翻译：

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利用当地和全球水文数据对 2018 年 7 月 6 日至 7 日洪水事件期间日本小田河流域的淹没情况进行分析

在 2018 年 7 月的第一周，大范围的洪水在日本西部的几个流域造成了广泛的破坏。受影响的流域包括冈山县织田河流域下游的仓敷市马备町地区。对此类历史洪水事件的分析可为适当的水资源管理提供有用的输入。因此，为了提高我们对 2018 年 7 月 5 日至 8 日强降雨期间小田河流域洪水淹没剖面的了解，使用了降雨-径流-淹没 (RRI) 模型，以及来自日本气象局的雷达降雨数据。机构 (JMA) 作为输入。小田河的河流几何形状——宽度、深度和堤防——被生成并应用于模拟。我们的结果表明，Mabicho 地区的洪水是由于回水效应和小田河沿岸的堤防破裂造成的。然后重新设计模型设置，将这些因素考虑在内。然后将模拟的最大洪水影响区与日本地理空间信息局 (GSI) 的数据进行比较，结果表明 RRI 模型估计的最大洪水淹没区与 GSI 洪水影响区密切匹配。从高分辨率数字高程模型 (DEM) 中提取河流几何形状，结合较粗分辨率的 DEM 数据（全球数据），然后用于在回水效应和堤防破坏的情况下对小田河流域进行水文模拟。虽然这种方法在本研究中产生了成功的结果，这是日本单个流域的案例研究。然而，这些结果提供了关于受洪水影响地区洪水淹没程度的有效信息，这一事实表明这种方法可以适用于任何流域。