In the unequal flow calculation, which is the basis of the flow capacity evaluation, various condition settings are set while performing the reproduction calculation of the past flood. However, in the lower reaches of the Jinzu River, cases have been confirmed in which sufficient reproducibility for past floods cannot be ensured, and the problems are thought to be the starting water level, low channel roughness coefficient, and riverbed decline during floods. Based on this, it was confirmed that it is effective in setting calculation conditions that reflect the actual conditions during floods by observing the vertical water level during floods, three-dimensional surveying of riverbeds, and observing and analyzing riverbed fluctuations.

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This study proposes a user-friendly method to implement river flow visualization measurement utilizing web-based geographic information. Existing geographic data products useful for field sur-vey are summarized. Since river bathymetry data is not covered in the existing geographic data products, a prototype of the digital elevation model covering a river bathymetry is proposed. Next, an example of how geographic information, specifically aerial photographs and digital elevation models, can be used for efficient river visualization measurement is presented. Finally, a summary of this study is presented, then key points when preparing new geographic information products, especially the digital elevation model covering bathymetry of rivers are discussed.

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