Ⅰ Introduction
The hydrographic geography research group can be the basis of hydrological research in a river basin by organizing and comparing natural (topographical geology, climate, hydrological) conditions, humanities, social conditions, etc. (hereinafter referred to as basin environment information), trying to create a "basin chorography". The purpose of creating a basin chorography is to clarify the environmental issues of the basin and its small basins, to show the direction of measures to maintain an appropriate environment, and to conduct a detailed survey based on them. It is to propose the ideal way of preserving the hydrological environment of the basin.
The basin is said to be the entire area where rain and snow fall, which is the source of the river water1), and is like a bowl where precipitation collects. Some are called large river basins such as first-class rivers and second-class rivers, while others are medium- and small-sized river basins, and in a broader sense, areas such as sewage and tap water are also basins. Furthermore, the degree of diffusion of population and social capital development varies depending on the basin. It is not easy to compare watersheds with different areas and social conditions, but with the generalization of GIS, watershed information has become easier to organize. In addition, the types of GIS data published are increasing year by year.
In this paper, we report a part of the result of organizing the basin environment information using the natural environment, hydrological environment, statistical data and GIS software published on the WEB, and propose the utilization measures.
Ⅱ Sites that can be used to create basin chorography
First, a website where basin environment information is published Etc. were investigated. An example of sites that can be used is shown (Table 1).
Ⅲ Organization of basin environment information by utilizing GIS
We suggest using QGIS. QGIS is used on various sites such as research, practice and management2) because it does not require a high license fee.Most of the public data is surface data for each attribute, so the size in the basin is fixed.
Generate a standard mesh and enter information such as terrain, geology, climate, and land use in the mesh. The merit of meshing is the area ratio of each information in the basin and its small basin. In addition, the rate of change can be calculated, making comparisons easy. As an example, the geological map of the Uono River basin, which is a tributary of the Shinano River, created from the 1/200,000 geological map of the national land survey is shown (Fig. 1).
Ⅳ Conclusion
We reported some of the results of organizing the basin environment information in mesh units for each basin and its small basins. These series of analyzes can be used not only as the basis of basin chorography, but also as basic materials for mass balance and water balance research for river basins, as well as simulations and floods of river floods and inland floods. It can also be used for disaster prevention and mitigation measures such as time outflow analysis. In the future, we would like to consider formulating the method using rasters with reference to topographical analysis and hydrological analysis using rasters3).
References
1) Takaharu NOMITSU ,Kinzou SENO (1959):New river studies ,CHIJIN SHOKAN CO . ,LTD .p .3
2) Yoichi MORIMOTO , Koji KODERA (2022):Environmental analysis using QGIS and 3D point cloud data , JOURNAL OF REGIONAL AND ENVIRONMENTAL SCIENCES ,Vol .1
3) Koji KODERA , Yusuke NAKAYAMA , Yuta SHIMIZU , Shin-ichi ONODERA(2008): A study on the GIS model for the water environment analysis of river basin- A case of Ashida river basin - ,Hosei University Information Media Education and Research Center Research Report ,Vol .21
